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Eaton Vance National Municipal Opportunities Trust

07/22/2021 | Press release | Distributed by Public on 07/22/2021 14:38

Amendment to Post-Effective Amendment (SEC Filing - 486BPOS)

As filed with the Securities and Exchange Commission on July 22, 2021

1933 Act File No. 333-234007

1940 Act File No. 811-22269

SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM N-2
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT of 1933
¨
PRE-EFFECTIVE AMENDMENT NO. ¨
POST-EFFECTIVE AMENDMENT NO. 3 x
and/or
REGISTRATION STATEMENT
UNDER
THE INVESTMENT COMPANY ACT OF 1940
o
AMENDMENT NO. 8 x
EATON VANCE NATIONAL MUNICIPAL OPPORTUNITIES TRUST
(Exact Name of Registrant as Specified in Charter)
Two International Place, Boston, Massachusetts 02110
(Address of Principal Executive Offices)
(617) 482-8260
(Registrant's Telephone Number)
Deidre E. Walsh
Two International Place, Boston, Massachusetts 02110
(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering: As soon as practicable after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans check the following box. ☐

If any securities being registered on this Form will be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act of 1933 ('Securities Act') other than securities offered in connection with a dividend reinvestment plan check the following box. ☑

If this Form is a registration statement pursuant to General Instruction A.2 or a post-effective amendment thereto check the following box. ☐

If this Form is a registration statement pursuant to General Instruction B or a post-effective amendment thereto that will become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act check the following box. ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction B to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act check the following box. ☐

It is proposed that this filing will become effective (check appropriate box):

☐ when declared effective pursuant to section 8(c)

If appropriate, check the following box:

☐ This post-effective amendment designates a new effective date for a previously filed registration statement.

This Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act and the Securities Act registration statement number of the earlier effective registration statement for the same offering is ________.
This Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, and the Securities Act registration statement number of the earlier effective registration statement for the same offering is________.
This Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, and the Securities Act registration statement number of the earlier effective registration statement for the same offering is 333-234007.

Check each box that appropriately characterizes the Registrant:

Registered Closed-End Fund (closed-end company that is registered under the Investment Company Act of 1940 (the 'Investment Company Act')).
Business Development Company (closed-end company that intends or has elected to be regulated as a business development company under the Investment Company Act.
Interval Fund (Registered Closed-End Fund or a Business Development Company that makes periodic repurchase offers under Rule 23c-3 under the Investment Company Act).

☑ A.2 Qualified (qualified to register securities pursuant to General Instruction A.2 of this Form).

☐ Well-Known Seasoned Issuer (as defined by Rule 405 under the Securities Act).

Emerging Growth Company (as defined by Rule 12b-2 under the Securities Exchange Act of 1934 ('Exchange Act').
If an Emerging Growth Company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of Securities Act.
New Registrant (registered or regulated under the Investment Company Act for less than 12 calendar months preceding this filing).

Prospectus Supplement

(To Prospectus dated July 22, 2021)

Eaton Vance National Municipal Opportunities Trust

Up to 1,142,873 Common Shares

Eaton Vance National Municipal Opportunities Trust (the 'Trust,' 'we,' or 'our') is a diversified, closed-end management investment company which commenced operations on May 27, 2009. Our primary investment objective is to provide current income exempt from federal income tax. Capital appreciation is a secondary objective.

The Trust has entered into a distribution agreement dated November 26, 2019 (the 'Distribution Agreement') with Eaton Vance Distributors, Inc. (the 'Distributor') relating to the common shares of beneficial interest (the 'Common Shares') offered by this Prospectus Supplement and the accompanying Prospectus dated July 22, 2021. The Distributor has entered into a dealer agreement, dated November 26, 2019, (the 'Dealer Agreement') with UBS Securities LLC (the 'Dealer') with respect to the Trust relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. In accordance with the terms of the Dealer Agreement, we may offer and sell our Common Shares, $0.01 par value per share, from time to time through the Dealer as sub-placement agent for the offer and sale of the Common Shares. Under the Investment Company Act of 1940, as amended (the '1940 Act'), the Trust may not sell any Common Shares at a price below the current net asset value of such Common Shares, exclusive of any distributing commission or discount.

Prior to March 1, 2021, the Distributor was a direct, wholly owned subsidiary of Eaton Vance Corp. ('EVC'). On March 1, 2021, Morgan Stanley acquired EVC (the 'Transaction') and the Distributor became an indirect, wholly owned subsidiary of Morgan Stanley.

Our Common Shares are listed on the New York Stock Exchange ('NYSE') under the symbol 'EOT.' As of July 20, 2021, the last reported sale price for our Common Shares on the NYSE was $23.14 per share.

Sales of our Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be 'at the market' as defined in Rule 415 under the Securities Act of 1933, as amended (the '1933 Act'), including sales made directly on the NYSE or sales made to or through a market maker other than on an exchange.

The Trust will compensate the Distributor with respect to sales of the Common Shares at a commission rate of 1.00% of the gross proceeds of the sale of Common Shares. The Distributor will compensate the Dealer out of this commission at a certain percentage rate of the gross proceeds of the sale of Common Shares sold under the Dealer Agreement, with the exact amount of such compensation to be mutually agreed upon by the Distributor and the Dealer from time to time. In connection with the sale of the Common Shares on the Trust's behalf, the Distributor may be deemed to be an 'underwriter' within the meaning of the 1933 Act and the compensation of the Dealer may be deemed to be underwriting commissions or discounts.

The Common Shares have traded both at a premium and a discount to net asset value ('NAV'). The Trust cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company's common stock (calculated within 48 hours of pricing). The Trust's issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust's Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Trust's Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors' risk of loss.

Investing in our securities involves certain risks. You could lose some or all of your investment. See 'Investment Objectives, Policies and Risks' beginning on page 25 of the accompanying Prospectus. You should consider carefully these risks together with all of the other information contained in this Prospectus Supplement and the accompanying Prospectus before making a decision to purchase our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus Supplement or the accompanying Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Prospectus Supplement dated July 22, 2021

This Prospectus Supplement, together with the accompanying Prospectus, sets forth concisely information about the Trust that you should know before investing. You should read this Prospectus Supplement and the accompanying Prospectus, which contain important information, before deciding whether to invest in our securities. You should retain the accompanying Prospectus and this Prospectus Supplement for future reference. A Statement of Additional Information ('SAI'), dated July 22, 2021 as supplemented from time to time, containing additional information about the Trust, has been filed with the Securities and Exchange Commission (the 'SEC') and is incorporated by reference in its entirety into this Prospectus Supplement and the accompanying Prospectus. This Prospectus Supplement, the accompanying Prospectus and the SAI are part of a 'shelf' registration statement that we filed with the SEC. This Prospectus Supplement describes the specific details regarding this offering (as defined below), including the method of distribution. If information in this Prospectus Supplement is inconsistent with the accompanying Prospectus or the SAI, you should rely on this Prospectus Supplement. You may request a free copy of the SAI, the table of contents of which is on page 56 of the accompanying Prospectus or a free copy of our annual and semi-annual reports to shareholders, obtain other information or make shareholder inquiries, by calling toll-free 1-800-262-1122 or by writing to the Trust at Two International Place, Boston, Massachusetts 02110. The Trust's SAI and annual and semi-annual reports also are available free of charge on our website at http://www.eatonvance.com and on the SEC's website (http://www.sec.gov). You may also obtain these documents, after paying a duplication fee, by electronic request at the following email address: [email protected]

Our securities do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

ii

TABLE OF CONTENTS

You should rely only on the information contained in, or incorporated by reference into, this Prospectus Supplement and the accompanying Prospectus in making your investment decisions. The Trust has not authorized any person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. The Trust is not making an offer to sell the securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this Prospectus Supplement and the accompanying Prospectus is accurate only as of the dates on their covers. The Trust's business, financial condition and prospects may have changed since the date of its description in this Prospectus Supplement or the date of its description in the accompanying Prospectus.

Prospectus Supplement
Prospectus Supplement Summary 1
Capitalization 2
Summary of Trust Expenses 3
Market and Net Asset Value Information 4
Use of Proceeds 5
Plan of Distribution 6
Legal Matters 6
Available Information 7
Prospectus
Prospectus Summary 6
Summary of Trust Expenses 21
Financial Highlights and Investment Performance 22
The Trust 24
Use of Proceeds 25
Portfolio Composition 25
Investment Objectives, Policies and Risks 25
Management of the Trust 44
Plan of Distribution 45
Distributions 46
Potential Conflicts of Interest 47
Federal Income Tax Matters 48
Dividend Reinvestment Plan 50
Description of Capital Structure 51
Custodian and Transfer Agent 56
Legal Matters 56
Reports to Shareholders 56
Independent Registered Public Accounting Firm 56
Additional Information 56
Table of Contents for the Statement of Additional Information 57
The Trust's Privacy Policy 58

Until August 16, 2021 (25 days after the date of this Prospectus Supplement), all dealers that buy, sell or trade the Common Shares, whether or not participating in this offering (as defined below), may be required to deliver the Prospectus and this Prospectus Supplement. This requirement is in addition to the dealers' obligation to deliver the Prospectus and this Prospectus Supplement when acting as underwriters and with respect to their unsold allotments or subscriptions.

iii

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus Supplement, the accompanying Prospectus and the SAI contain 'forward-looking statements.' Forward-looking statements can be identified by the words 'may,' 'will,' 'intend,' 'expect,' 'estimate,' 'continue,' 'plan,' 'anticipate,' and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus Supplement as well as in the accompanying Prospectus. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the 'Investment Objectives, Policies and Risks' section of the accompanying Prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus Supplement or the accompanying Prospectus are made as of the date of this Prospectus Supplement or the accompanying Prospectus, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus Supplement, the accompanying Prospectus and the SAI are excluded from the safe harbor protection provided by section 27A of the 1933 Act.

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the 'Investment Objectives, Policies and Risks' section of the accompanying Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

iv

Prospectus Supplement Summary

The following summary is qualified in its entirety by reference to the more detailed information included elsewhere in this Prospectus Supplement and in the accompanying Prospectus and in the SAI.

THE TRUST

Eaton Vance National Municipal Opportunities Trust (the 'Trust,' 'we,' or 'our') is a diversified, closed-end management investment company, which commenced operations on May 27, 2009. The Trust's primary investment objective is to provide current income exempt from federal income tax. Capital appreciation is a secondary objective. Investments are based on Eaton Vance Management's ('Eaton Vance' or the 'Adviser') research and ongoing credit analysis, the underlying materials which are generally not available to individual investors. An investment in the Trust may not be appropriate for all investors, and there is no assurance that the Trust will achieve its investment objectives.

THE ADVISER

Eaton Vance acts as the Trust's investment adviser under an Investment Advisory and Administrative Agreement (the 'Advisory Agreement'). The Adviser's principal office is located at Two International Place, Boston, MA 02110. Eaton Vance, its affiliates and predecessor companies have been managing assets of individuals and institutions since 1924 and of investment companies since 1931. Prior to March 1, 2021, Eaton Vance was a wholly owned subsidiary of Eaton Vance Corp. ('EVC').

On March 1, 2021, Morgan Stanley acquired EVC (the 'Transaction') and Eaton Vance became an indirect, wholly owned subsidiary of Morgan Stanley. In connection with the Transaction, the Trust entered into a new investment advisory and administrative agreement with Eaton Vance. The agreement was approved by shareholders prior to the consummation of the Transaction and was effective upon its closing. Effective March 1, 2021, any fee reduction agreement previously applicable to the Trust was incorporated into its new investment advisory and administrative agreement with Eaton Vance.

Morgan Stanley (NYSE: MS), whose principal offices are at 1585 Broadway, New York, New York 10036, is a preeminent global financial services firm engaged in securities trading and brokerage activities, as well as providing investment banking, research and analysis, financing and financial advisory services. As of March 31, 2021, Morgan Stanley's asset management operations had aggregate assets under management of approximately $1.4 trillion.

Under the general supervision of the Trust's Board, Eaton Vance is responsible for managing the Trust's overall investment program, determining the Trust's allocations among its permitted investments, and selecting individual holdings. The Adviser will furnish to the Trust investment advice and office space and all necessary office facilities, equipment and personnel for servicing the investments of the Trust and for administering its affairs. The Adviser will compensate all Trustees and officers of the Trust who are members of the Adviser's organization and will also compensate all other Adviser personnel who provide research and investment services to the Trust. Pursuant to the Advisory Agreement, the Trust pays the Adviser a fee calculated as a percentage of the Trust's average daily gross assets in return for these investment advisory services, facilities and payments. The Trust's advisory fee currently is computed at an annual rate of 0.60% of the Trust's average daily gross assets up to and including $1.5 billion and 0.59% of average daily gross assets over $1.5 billion. For purposes of this calculation, 'gross assets' of the Trust shall mean total assets of the Trust, including any form of investment leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to investment leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means, all as determined in accordance with generally accepted accounting principles.

THE OFFERING

The Trust has entered into a distribution agreement dated November 26, 2019 (the 'Distribution Agreement') with Eaton Vance Distributors, Inc. (the 'Distributor') relating to the common shares of beneficial interest (the 'Common Shares'), offered by this Prospectus Supplement and the accompanying Prospectus dated July 22, 2021 (the 'Offering'). The Distributor has entered into a dealer agreement dated November 26, 2019 (the 'Dealer Agreement') with UBS Securities LLC (the 'Dealer') with respect to the Trust relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. In accordance with the terms of the Dealer Agreement, the Trust may offer and sell up to 1,142,873 Common Shares, par value $0.01 per Common Share, from time to time through the Dealer as sub-placement agent for the offer and sale of the Common Shares.

1

Offerings of the Common Shares will be subject to the provisions of the 1940 Act, which generally require that the public offering price of common shares of a closed-end investment company (exclusive of distribution commissions and discounts) must equal or exceed the net asset value per share of the company's common shares (calculated within 48 hours of pricing), absent shareholder approval or under certain other circumstances.

Sales of the Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be 'at the market' as defined in Rule 415 under the 1933 Act, including sales made directly on the New York Stock Exchange ('NYSE') or sales made to or through a market maker other than on an exchange. The Common Shares may not be sold through agents, underwriters or dealers without delivery or deemed delivery of a Prospectus and an accompanying Prospectus Supplement describing the method and terms of the offering of Common Shares.

Prior to March 1, 2021, the Distributor was a direct, wholly owned subsidiary of EVC. Upon the closing of the Transaction on March 1, 2021, the Distributor became an indirect, wholly owned subsidiary of Morgan Stanley.

LISTING AND SYMBOL

The Trust's currently outstanding Common Shares are listed on the NYSE under the symbol 'EOT.' Any new Common Shares offered and sold hereby are expected to be listed on the NYSE and trade under this symbol. The net asset value of the Common Shares on July 20, 2021 was $22.55 per share. As of July 20, 2021, the last reported sale price for the Common Shares was $23.14.

USE OF PROCEEDS

The Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus Supplement in accordance with its investment objectives and policies as described in the accompanying Prospectus under 'Investment Objectives, Policies and Risks' within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust's distribution to the holders of Common Shares ('Common Shareholders') or result in a distribution consisting principally of a return of capital.

Capitalization

We may offer and sell up to 1,142,873 of our Common Shares, $0.01 par value per share, from time to time through the Dealer as sub-placement agent under this Prospectus Supplement and the accompanying Prospectus. Of the 1,142,873 Common Shares, 151,865 have been issued and 991,008 are unsold. In addition, the Trust has registered, and may take down, additional shares at a later date. There is no guarantee that there will be any sales of our Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. The table below assumes that we will sell 991,008 Common Shares at a price of $23.14 per share (the last reported sale price per share of our Common Shares on the NYSE on July 20, 2021). Actual sales, if any, of our Common Shares under this Prospectus Supplement and the accompanying Prospectus may be greater or less than $23.14 per share, depending on the market price of our Common Shares at the time of any such sale. To the extent that the market price per share of our Common Shares on any given day is less than the net asset value per share on such day, we will instruct the Dealer not to make any sales on such day.

2

The following table sets forth our capitalization:

• on a historical basis as of March 31, 2021 (audited); and

• on a pro forma as adjusted basis to reflect the assumed sale of 991,008 Common Shares at $23.14 per share (the last reported sale price for our Common Shares on the NYSE on July 20, 2021), in an offering under this Prospectus Supplement and the accompanying Prospectus, after deducting the assumed commission of $229,319 (representing an estimated commission to the Distributor of 1.00% of the gross proceeds of the sale of Common Shares, of which a certain percentage will be paid to the Dealer in connection with sales of Common Shares effected in this Offering).

As of

March 31, 2021

(audited)

Pro Forma

(unaudited)

Actual As adjusted
Net Assets $ 333,178,201 $ 355,880,807
$0.01 par value per share of common shares outstanding $ 153,327 $ 163,237
Additional paid-in capital $ 291,757,902 $ 314,460,508
Distributable earnings $ 41,266,972 $ 41,257,062
Net Assets $ 333,178,201 $ 355,880,807
Net asset value per share $21.73 $21.80
Common shares issued and outstanding 15,332,688 16,323,696

Summary of Trust Expenses

The purpose of the table below is to help you understand all fees and expenses that you, as a holder of Common Shares ('Common Shareholder'), would bear directly or indirectly. The table reflects leverage attributable to floating-rate notes for the fiscal year ended March 31, 2021 in an amount equal to 6.10% of the Trust's gross assets (including floating-rate notes) and shows Trust expenses as a percentage of net assets attributable to Common Shares.

Common Shareholder transaction expenses
Sales load paid by you (as a percentage of offering price) 1.00% (1)
Offering expenses (as a percentage of offering price) None(2)
Dividend reinvestment plan fees $5.00(3)
Annual expenses Percentage of net assets
attributable to Common Shares(4)
Investment advisory fee 0.64%(5)
Interest expenses 0.05%(6)
Other expenses 0.09%
Total annual Trust operating expenses 0.78%
3

EXAMPLE

The following example illustrates the expenses that Common Shareholders would pay on a $1,000 investment in Common Shares, assuming (i) total annual expenses of 0.78% of net assets attributable to Common Shares in years 1 through 10; (ii) a sales load of 1.00%; (iii) a 5% annual return; and (iv) all distributions are reinvested at NAV:

1 Year 3 Years 5 Years 10 Years
$18 $35 $53 $106

The above table and example and the assumption in the example of a 5% annual return are required by regulations of the SEC that are applicable to all investment companies; the assumed 5% annual return is not a prediction of, and does not represent, the projected or actual performance of the Trust's Common Shares. For more complete descriptions of certain of the Trust's costs and expenses, see 'Management of the Trust.' In addition, while the example assumes reinvestment of all dividends and distributions at NAV, participants in the Trust's dividend reinvestment plan may receive Common Shares purchased or issued at a price or value different from NAV. See 'Distributions' and 'Dividend Reinvestment Plan.' The example does not include estimated offering costs, which would cause the expenses shown in the example to increase.

The example should not be considered a representation of past or future expenses, and the Trust's actual expenses may be greater or less than those shown. Moreover, the Trust's actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

___________

(1) Represents the estimated commission with respect to the Trust's Common Shares being sold in this Offering. There is no guarantee that there will be any sales of the Trust's Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales of the Trust's Common Shares under this Prospectus Supplement and the accompanying Prospectus, if any, may be less than as set forth under 'Capitalization' above. In addition, the price per share of any such sale may be greater or less than the price set forth under 'Capitalization' above, depending on market price of the Trust's Common Shares at the time of any such sale.
(2) Eaton Vance will pay the expenses of the Offering (other than the applicable commissions); therefore Offering expenses are not included in the Summary of Trust Expenses. Offering expenses generally include, but are not limited to, the preparation, review and filing with the SEC of the Trust's registration statement (including this Prospectus Supplement, the accompanying Prospectus and the SAI), the preparation, review and filing of any associated marketing or similar materials, costs associated with the printing, mailing or other distribution of this Prospectus Supplement, the accompanying Prospectus, the SAI and/or marketing materials, associated filing fees, NYSE listing fees, and legal and auditing fees associated with the Offering.
(3) You will be charged a $5.00 service charge and pay brokerage charges if you direct the plan agent to sell your Common Shares held in a dividend reinvestment account.
(4) Stated as a percentage of average net assets attributed to Common Shares for the year ended March 31, 2021.
(5) The advisory fee paid by the Trust to the Adviser is based on the average daily gross assets of the Trust, including all assets attributable to any form of investment leverage that the Trust may utilize. Accordingly, if the Trust were to increase investment leverage in the future, the advisory fee will increase as a percentage of net assets.
(6) 'Interest Expenses' relate to the Trust's liability with respect to floating-rate notes held by third parties in conjunction with investments in residual interest bonds. The Trust records offsetting interest income in an amount at least equal to this expense relating to the municipal obligations underlying such transactions.

Market and Net Asset Value Information

Our Common Shares are listed on the NYSE under the symbol 'EOT.' Our Common Shares commenced trading on the NYSE in 2009.

Our Common Shares have traded both at a premium and a discount to net asset value or NAV. We cannot predict whether our shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of Common Shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company's common stock (calculated within 48 hours of pricing). Our issuance of Common Shares may have an adverse effect on prices in the secondary market for our Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for our Common Shares. Shares of Common Stock of closed-end investment companies frequently trade at a discount from NAV. See 'Prospectus Summary-Special Risk Considerations-Discount from or premium to NAV' on page 11 of the accompanying Prospectus.

4

The following table sets forth for the period indicated the high and low closing market prices for Common Shares on the NYSE, and the corresponding NAV per share and the premium or discount to NAV per share at which the Trust's Common Shares were trading as of the same date. NAV is determined no less frequently than daily, generally on each day of the week that the NYSE is open for trading. See 'Determination of Net Asset Value' on page 24 of the accompanying SAI for information as to the determination of the Trust's net asset value.

Market Price NAV per Share on Date of Market Price NAV Premium/(Discount) on Date of Market Price
Quarter Ended High Low High Low High Low
June 30, 2021 $23.45 $22.09 $22.11 $22.23 6.06% (0.63)%

The last reported sale price, NAV per share and percentage premium/(discount) to NAV per share of the Common Shares as of July 20, 2021, were $23.14, $22.55 and 2.62%, respectively. As of July 20, 2021, the Trust had 15,396,359 Common Shares outstanding and net assets of the Trust were $347,118,606.

The following table provides information about our outstanding Common Shares as of July 20, 2021:

Title of Class Amount Authorized Amount Held by the Trust or for its Account Amount Outstanding
Common Shares Unlimited 0 15,396,359

Use of Proceeds

Sales of our Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be 'at the market' as defined in Rule 415 under the 1933 Act, including sales made directly on the NYSE or sales made to or through a market maker other than on an exchange. There is no guarantee that there will be any sales of our Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales, if any, of our Common Shares under this Prospectus Supplement and the accompanying Prospectus may be less than as set forth below in this paragraph. In addition, the price per share of any such sale may be greater or less than the price set forth in this paragraph, depending on the market price of our Common Shares at the time of any such sale. As a result, the actual net proceeds we receive may be more or less than the amount of net proceeds estimated in this Prospectus Supplement. Assuming the sale of all of the Common Shares offered under this Prospectus Supplement and the accompanying Prospectus, at the last reported sale price of $23.14 per share for our Common Shares on the NYSE as of July 20, 2021, we estimate that the net proceeds of this Offering will be approximately $22,702,606 after deducting the estimated sales load and the estimated offering expenses payable by the Trust, if any.

Subject to the remainder of this section, the Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus Supplement in accordance with its investment objectives and policies as described in the accompanying Prospectus under 'Investment Objectives, Policies and Risks' within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust's distribution to Common Shareholders or result in a distribution consisting principally of a return of capital.

5

Plan of Distribution

Under the Dealer Agreement between the Distributor and the Dealer, upon written instructions from the Distributor, the Dealer will use its reasonable best efforts, to sell, as sub-placement agent, the Common Shares under the terms and subject to the conditions set forth in the Dealer Agreement. The Dealer's solicitation will continue until the Distributor instructs the Dealer to suspend the solicitations and offers. The Distributor will instruct the Dealer as to the amount of Common Shares to be sold by the Dealer. The Distributor may instruct the Dealer not to sell Common Shares if the sales cannot be effected at or above the price designated by the Distributor in any instruction. To the extent that the market price per share of the Trust's Common Shares on any given day is less than the net asset value per share on such day, the Distributor will instruct the Dealer not to make any sales on such day. The Distributor or the Dealer may suspend the offering of Common Shares upon proper notice and subject to other conditions.

The Dealer will provide written confirmation to the Distributor following the close of trading on the day on which Common Shares are sold under the Dealer Agreement. Each confirmation will include the number of shares sold on the preceding day, the net proceeds to the Trust and the compensation payable by the Distributor to the Dealer in connection with the sales.

The Trust will compensate the Distributor with respect to sales of the Common Shares at a commission rate of 1.00% of the gross proceeds of the sale of Common Shares. The Distributor will compensate the Dealer for its services in acting as sub-placement agent in the sale of Common Shares out of this commission at a certain percentage rate of the gross proceeds of the sale of Common Shares sold under the Dealer Agreement, with the exact amount of such compensation to be mutually agreed upon by the Distributor and the Dealer from time to time. There is no guarantee that there will be any sales of the Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales, if any, of the Common Shares under this Prospectus Supplement and the accompanying Prospectus may be conducted at a price that is greater or less than the last reported sale price set forth in this Prospectus Supplement, depending on the market price of Common Shares at the time of any such sale. Eaton Vance will pay the expenses of the Offering (other than the applicable commissions).

Settlement for sales of Common Shares will occur on the second trading day following the date on which such sales are made, in return for payment of the net proceeds to the Trust. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

The Distributor has agreed to provide indemnification and contribution to the Dealer against certain civil liabilities, including liabilities under the 1933 Act.

The Dealer Agreement will remain in full force and effect unless terminated by either party upon 5 days' written notice to the other party.

The principal business address of the Dealer is 1285 Avenue of the Americas, New York, NY 10019.

The Dealer and its affiliates hold or may hold in the future, directly or indirectly, investment interests in the Distributor and its funds. The interests held by the Dealer or its affiliates are not attributable to, and no investment discretion is held by, the Dealer or its affiliates.

Legal Matters

Certain legal matters in connection with the Common Shares will be passed upon for the Trust by internal counsel for Eaton Vance.

6

Available Information

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the 'Exchange Act'), and the 1940 Act and are required to file reports, including annual and semi-annual reports, proxy statements and other information with the SEC. These documents are available on the SEC's EDGAR system.

This Prospectus Supplement, the accompanying Prospectus and the SAI do not contain all of the information in our registration statement, including amendments, exhibits, and schedules that the Trust has filed with the SEC (File No. 333-234007). Statements in this Prospectus Supplement and the accompanying Prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the copy of the contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by this reference.

Additional information about us can be found in our registration statement (including amendments, exhibits, and schedules) on Form N-2 filed with the SEC. The SEC maintains a web site (http://www.sec.gov) that contains our registration statement, other documents incorporated by reference, and other information we have filed electronically with the SEC, including proxy statements and reports filed under the Exchange Act.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund's annual and semi-annual shareholder reports are no longer being sent by mail unless you specifically request paper copies of the reports. Instead, the reports are being made available on the Fund's website (funds.eatonvance.com/closed-end-fund-and-term-trust-documents.php), and you will be notified by mail each time a report is posted and provided with a website address to access the report. If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. If you hold shares at the Fund's transfer agent, American Stock Transfer & Trust Company, LLC ('AST'), you may elect to receive shareholder reports and other communications from the Fund electronically by contacting AST. If you own your shares through a financial intermediary (such as a broker-dealer or bank), you must contact your financial intermediary to sign up. You may elect to receive all future Fund shareholder reports in paper free of charge. If you hold shares at AST, you can inform AST that you wish to continue receiving paper copies of your shareholder reports by calling 1-866-439-6787. If you own these shares through a financial intermediary, you must contact your financial intermediary or follow instructions included with this disclosure, if applicable, to elect to continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held with AST or to all funds held through your financial intermediary, as applicable.

7

(BASE PROSPECTUS)

Up to 2,285,745 Shares

Eaton Vance National Municipal Opportunities Trust

Common Shares

Investment Objectives and Policies. Eaton Vance National Municipal Opportunities Trust (the 'Trust') is a diversified, closed-end management investment company, which commenced operations on May 27, 2009. The Trust's primary investment objective is to provide current income exempt from federal income tax. Capital appreciation is a secondary objective. The Trust will invest primarily in municipal obligations that, at the time of investment, are investment grade quality. The Trust also may invest a portion of its assets in municipal obligations rated below investment grade quality or unrated securities that the Trust's investment adviser considers to be of comparable quality. The Trust's net asset value ('NAV') and distribution rate will vary and may be affected by several factors, including changes in interest rates and the credit quality of municipal issuers. Fluctuations in NAV may be magnified as a result of the Trust's use of leverage, which is a speculative investment technique. An investment in the Trust may not be appropriate for all investors, particularly those that are not subject to federal income tax. There is no assurance that the Trust will achieve its investment objectives.

Investment Adviser. The Trust's investment adviser is Eaton Vance Management ('Eaton Vance' or the 'Adviser'). Prior to March 1, 2021, Eaton Vance was a wholly owned subsidiary of Eaton Vance Corp. ('EVC'). On March 1, 2021, Morgan Stanley acquired EVC (the 'Transaction') and Eaton Vance became an indirect, wholly owned subsidiary of Morgan Stanley.

Morgan Stanley (NYSE: MS), whose principal offices are at 1585 Broadway, New York, New York 10036, is a preeminent global financial services firm engaged in securities trading and brokerage activities, as well as providing investment banking, research and analysis, financing and financial advisory services. As of March 31, 2021, Morgan Stanley's asset management operations had aggregate assets under management of approximately $1.4 trillion.

The Offering. The Trust may offer, from time to time, in one or more offerings (each, an 'Offering'), the Trust's common shares of beneficial interest, $0.01 par value ('Common Shares'). Common Shares may be offered at prices and on terms to be set forth in one or more supplements to this Prospectus (each, a 'Prospectus Supplement'). You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by us, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. The Trust may not sell any Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of the Common Shares. (continued on inside cover page)

The Common Shares have traded both at a premium and a discount to net asset value ('NAV'). The Trust cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the Investment Company Act of 1940, as amended (the '1940 Act'), generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company's common stock (calculated within 48 hours of pricing). The Trust's issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust's Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Trust's Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors' risk of loss.

Investing in shares involves certain risks, including that the Trust will invest substantial portions of its assets in below investment grade quality securities with speculative characteristics. See 'Investment Objectives, Policies and Risks' beginning at page 25 and 'Below Investment Grade Securities Risk' on page 14.

Neither the Securities and Exchange Commission ('SEC') nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

(continued from previous page)

Portfolio Contents. During normal market conditions, the Trust will invest at least 80% of its gross assets in debt obligations issued by or on behalf of states, territories and possessions of the United States, including the District of Columbia, and their political subdivisions, agencies or instrumentalities, the interest on which is exempt from regular federal income tax ('municipal obligations'), including investments in residual interest bonds whose interest is exempt from regular federal income tax. During normal market conditions, at least 70% of the Trust's investments in municipal obligations will be investment grade quality at the time of investment. Up to 30% of the Trust's investments in municipal obligations may be below investment grade quality at the time of investment. Up to 20% of the Trust's investments in municipal obligations may be subject to the alternative minimum tax.

A municipal obligation is considered investment grade quality if it is either (i) rated within the four highest ratings categories by at least one nationally recognized statistical rating organization (a 'Rating Agency'), which are those rated Baa or higher by Moody's Investors Service, Inc. ('Moody's') or BBB or higher by Standard & Poor's Ratings Services ('S&P') or Fitch Ratings ('Fitch'), or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of investment grade quality. If a municipal obligation is rated differently by two or more Rating Agencies, the Trust will use the higher of such ratings (the 'Municipal Obligation Rating'). If a municipal obligation is insured, the Trust will use the higher of the Municipal Obligation Rating or the insurance issuer's rating. Securities rated in the fourth highest category (i.e., Baa by Moody's or BBB by S&P or Fitch) are considered investment grade quality, but may have speculative characteristics. A municipal obligation is considered below investment grade quality if it is either (i) rated below investment grade by a Rating Agency, or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of comparable quality. Municipal obligations of below investment grade quality (commonly referred to as 'junk' bonds) involve special risks as compared to municipal obligations of investment grade quality. These risks include greater sensitivity to a general economic downturn, greater market price volatility and less secondary market trading. The Trust may invest in below investment grade municipal obligations of any quality. This means that the Trust's investments in municipal obligations may include securities of issuers that are having financial difficulties, which may include being in default on obligations to pay principal or interest thereon when due or involved in bankruptcy or insolvency proceedings (such securities are commonly referred to as 'distressed securities').

Leverage. The Trust currently uses leverage to seek to enhance returns by investing in residual interest bonds. The Trust will not utilize leverage in excess of 15% of its gross assets. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. Although the Trust has no current intention to do so, the Trust is authorized also to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act.

The Adviser anticipates that the use of leverage (from residual interest bonds) may result in higher income to holders of Common Shares ('Common Shareholders') over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful. The investment advisory fee paid to Eaton Vance will be calculated on the basis of the Trust's average daily gross assets. 'Gross assets' of the Trust means total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. This means that the Trust's advisory fees will be higher when leverage is utilized which may create an incentive for the Adviser to employ leverage. In this regard, holders of debt or preferred shares do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds from the use of leverage, which means that Common Shareholders effectively bear the entire advisory fee. See 'Investment Objectives, Policies and Risks - Use of Leverage and Related Risks' at page 32, 'Investment Objectives, Policies and Risks - Additional Risk Considerations' at page 35 and 'Description of Capital Structure' at page 51.

Exchange Listing. As of July 20, 2021, the Trust had 15,396,359 Common Shares outstanding, which are traded on the New York Stock Exchange ('NYSE') under the symbol 'EOT.' As of July 20, 2021, the last reported sales price of a Common Share of the Trust on the NYSE was $23.14. Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

Eaton Vance National Municipal Opportunities Trust 2 Prospectus dated July 22,2021

This Prospectus, together with any applicable Prospectus Supplement, sets forth concisely information you should know before investing in the shares of the Trust. Please read and retain this Prospectus for future reference. A Statement of Additional Information ('SAI') dated July 22, 2021, has been filed with the SEC and is incorporated by reference into this Prospectus. You may request a free copy of the SAI, the table of contents of which is on page 56 of this Prospectus, a free copy of our annual and semi-annual reports to shareholders, obtain other information or make shareholder inquiries, by calling toll-free 1-800-262-1122 or by writing to the Trust at Two International Place, Boston, Massachusetts 02110. The Trust's SAI and annual and semi-annual reports also are available free of charge on our website at http://www.eatonvance.com and on the SEC's website (http://www.sec.gov). You may also obtain these documents, after paying a duplication fee, by electronic request at the following email address: [email protected]

The Trust's shares do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

You should rely only on the information contained or incorporated by reference in this Prospectus. The Trust has not authorized anyone to provide you with different information. The Trust is not making an offer of these securities in any jurisdiction where the offer is not permitted. You should not assume that the information contained in this Prospectus is accurate as of any date other than the date on the front of this Prospectus.

Eaton Vance National Municipal Opportunities Trust 3 Prospectus dated July 22,2021

Table of Contents

Prospectus Summary 6
Summary of Trust Expenses 21
Financial Highlights and Investment Performance 22
The Trust 24
Use of Proceeds 25
Portfolio Composition 25
Investment Objectives, Policies and Risks 25
Management of the Trust 44
Plan of Distribution 45
Distributions 46
Potential Conflicts of Interest 47
Federal Income Tax Matters 48
Dividend Reinvestment Plan 50
Description of Capital Structure 51
Custodian and Transfer Agent 56
Legal Matters 56
Reports to Shareholders 56
Independent Registered Public Accounting Firm 56
Additional Information 56
Table of Contents for the Statement of Additional Information 57
The Trust's Privacy Policy 58
Eaton Vance National Municipal Opportunities Trust 4 Prospectus dated July 22,2021

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus, any accompanying Prospectus Supplement and the SAI contain 'forward-looking statements.' Forward-looking statements can be identified by the words 'may,' 'will,' 'intend,' 'expect,' 'estimate,' 'continue,' 'plan,' 'anticipate,' and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus as well as in any accompanying Prospectus Supplement. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the 'Investment Objectives, Policies and Risks' section of this Prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus or any accompanying Prospectus Supplement are made as of the date of this Prospectus or the accompanying Prospectus Supplement, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus, any accompanying Prospectus Supplement and the SAI are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended (the '1933 Act').

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the 'Investment Objectives, Policies and Risks' section of this Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

Prospectus dated July 22, 2021

Eaton Vance National Municipal Opportunities Trust 5 Prospectus dated July 22,2021

Prospectus Summary

The following summary is qualified in its entirety by reference to the more detailed information included elsewhere in this Prospectus, in any related Prospectus Supplement, and in the SAI.

THE TRUST

Eaton Vance National Municipal Opportunities Trust (the 'Trust') is a diversified, closed-end management investment company, which commenced operations on May 27, 2009. The Trust's investment objective is to provide current income exempt from federal income tax with capital appreciation as a secondary objective. Investments are based on the municipal securities research, trading and portfolio management of the Trust's investment adviser, Eaton Vance Management ('Eaton Vance' or the 'Adviser'), which generally are not available to individual investors. The Trust's NAV and distribution rate will vary and may be affected by several factors, including changes in interest rates and the credit quality of municipal issuers. An investment in the Trust may not be appropriate for all investors, particularly those that are not subject to federal income tax. There is no assurance that the Trust will achieve its investment objectives.

THE OFFERING

The Trust may offer, from time to time, in one or more offerings (each, an 'Offering'), up to 2,285,745 of the Trust's common shares of beneficial interest, $0.01 par value ('Common Shares'), on terms to be determined at the time of the Offering. The Common Shares may be offered at prices and on terms to be set forth in one or more prospectus supplements. You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by the Trust, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. See 'Plan of Distribution.' The Trust may not sell any of Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of Common Shares.

INVESTMENT OBJECTIVES, POLICIES AND RISKS

Investment Objectives. The Trust's primary investment objective is to provide current income exempt from federal income tax. The Trust's secondary investment objective is capital appreciation. The Trust will seek to achieve its investment objectives by investing primarily in municipal obligations (as defined below) that, at the time of investment, are investment grade quality. The Trust also may invest a portion of its gross assets in municipal obligations rated below investment grade or unrated securities that the Adviser considers to be of comparable quality. There is no assurance that the Trust will achieve its investment objectives.

Portfolio Parameters. During normal market conditions, the Trust will invest at least 80% of its gross assets in debt obligations issued by or on behalf of states, territories and possessions of the United States, including the District of Columbia, and their political subdivisions, agencies or instrumentalities, the interest on which is exempt from regular federal income tax ('municipal obligations'). For purposes of this 80% policy, municipal obligations will include investments in residual interest bonds whose interest is exempt from regular federal income tax.

The Trust's investment objectives are considered a non-fundamental policy that may be changed by the Trust's Board of Trustees (the 'Board') without approval of the holders of the Trust's common shares ('Common Shareholder'). The Trust's policy of investing at least 80% of its gross assets in municipal obligations is considered fundamental and may only be changed upon Common Shareholder approval.

Municipal obligations include bonds, notes and commercial paper issued by a municipality, a group of municipalities or participants in qualified issues of municipal debt for a wide variety of both public and private purposes, the interest on which is exempt from regular federal income tax. Public purpose municipal bonds include general obligation and revenue bonds. Issuers of general obligation bonds include states, counties, cities, towns and regional districts. The proceeds of these obligations are used to fund a wide range of public projects, including the construction or improvement of schools, highways and roads, water and sewer systems and a variety of other public purposes. The basic security of general obligation bonds is the issuer's pledge of its faith, credit, and taxing power for the payment of principal and interest. The taxes that can be levied for the payment of debt service may be limited or unlimited as to rate an amount. Revenue bonds are backed by the revenues of a project or facility, or from the proceeds of a specific revenue source. Some revenue bonds are payable solely or partly from funds that are subject to annual appropriations by a state's legislature. Municipal notes include bond anticipation, tax anticipation and revenue anticipation notes. Bond, tax and revenue anticipation notes

Eaton Vance National Municipal Opportunities Trust 6 Prospectus dated July 22,2021

are short-term obligations that will be retired with the proceeds of an anticipated bond issue, tax revenue or facility revenue, respectively. Certain types of bonds are issued by or on behalf of public authorities to finance various privately owned or operated facilities, including certain facilities for the local furnishing of electric energy or gas, sewage facilities, solid waste disposal facilities and other specialized facilities. The Trust may purchase municipal obligations in the form of bonds, notes, leases or certificates of participation; structured as callable or non-callable; with payment forms that include fixed coupon, variable rate, zero-coupon, capital appreciation bonds, residual interest bonds and short-term floating-rate securities. Such municipal obligations may be acquired through investments in pooled vehicles, partnerships, or other investment companies. No established resale market exists for certain of the municipal obligations in which the Trust may invest. The Trust has no limitation on the amount of its assets that may be invested in securities that are not readily marketable or are subject to restrictions on resale.

During normal market conditions, at least 70% of the Trust's investments in municipal obligations will be investment grade quality at time of investment. A municipal obligation is considered investment grade quality if it is either (i) rated within the four highest ratings categories by at least one nationally recognized statistical rating organization (a 'Rating Agency'), which are those rated Baa or higher by Moody's Investors Service, Inc. ('Moody's') or BBB or higher by Standard & Poor's Ratings Services ('S&P') or Fitch Ratings ('Fitch'), or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of investment grade quality. If a municipal obligation is rated differently by two or more Rating Agencies, the Trust will use the higher of such ratings (the 'Municipal Obligation Rating'). If a municipal obligation is insured, the Trust will use the higher of the Municipal Obligation Rating or the insurance issuer's rating. Securities rated in the fourth highest category (i.e., Baa by Moody's or BBB by S&P or Fitch) are considered investment grade quality, but may have speculative characteristics.

Up to 30% of the Trust's investments in municipal obligations may be below investment grade quality at time of investment. A municipal obligation is considered below investment grade quality if it is either (i) rated below investment grade by a Rating Agency, or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of comparable quality. Municipal obligations of below investment grade quality (commonly referred to as 'junk' bonds) involve special risks as compared to municipal obligations of investment grade quality. These risks include greater sensitivity to a general economic downturn, greater market price volatility and less secondary market trading. The Trust may invest in below investment grade municipal obligations of any quality. This means that the Trust's investments in municipal obligations may include securities of issuers that are having financial difficulties, which may include being in default on obligations to pay principal or interest thereon when due or involved in bankruptcy or insolvency proceedings (such securities are commonly referred to as 'distressed securities').

Under normal market conditions, the Trust will seek to maintain an average credit quality of investment grade. As indicated above, the Trust may invest in unrated obligations for which Eaton Vance will make a credit quality determination for purposes of the Trust's credit quality policy. To the extent that the Trust invests in such unrated obligations, the Trust's credit quality will be more dependent on Eaton Vance's credit analysis than if the Trust invested in only rated obligations. For a description of the risks of investing in below investment grade securities, see 'Investment Objectives, Policies and Risks - Risk Considerations - Below Investment Grade Securities Risk.'

Up to 20% of the Trust's investments in municipal obligations may be subject to the alternative minimum tax.

Up to 5% of the Trust's investments in municipal obligations may be collateralized by the proceeds from class action or other litigation against the tobacco industry. Such municipal obligations are backed solely by expected revenues to be derived from lawsuits involving tobacco-related deaths and illnesses which were settled between certain states and American tobacco companies.

The Trust invests in residual interest bonds, also known as inverse floating rate securities, which have the economic effect of leverage. A residual interest bond is a type of inverse floating-rate security created by dividing the income from a municipal bond into two portions. Typically, a third-party sponsor will create a trust (commonly referred to as a tender option bond trust) consisting of one or more municipal bonds and then create two new securities: a short-term floating-rate security and a residual interest inverse floating-rate bond. The short-term floating rate security will be linked to a reference interest rate (such as the London Interbank Offered Rate ('LIBOR') or the Securities Industry and Financial Markets Association ('SIFMA') Municipal Bond Swap Index), and the tender option bond trust's income will be used to pay the coupon on the short-term floating rate security, with any remaining income going toward the residual interest bond. Because the residual interest bond is an inverse floating rate security and only pays a residual income, compared to fixed rate municipal bonds, the value of residual interest bonds will fluctuate to a greater extent in response to changes in prevailing long-term interest rates. As market interest rates increase, the value of a residual interest bond will decrease. Moreover, the income earned on such bonds will fluctuate in response to changes in prevailing short-term interest rates. When residual interest bonds are held by the Trust, an increase in short- or long-term market interest rates may adversely affect the income received from such bonds or the NAV of Common Shares.

Eaton Vance National Municipal Opportunities Trust 7 Prospectus dated July 22,2021

If the Trust invests 25% or more of its gross assets in any one state (or U.S. territory) the Trust may be more susceptible to adverse economic, political or regulatory occurrences affecting a particular state (or territory).

The Trust generally will not invest more than 2% of its gross assets in any security of below investment grade quality.

'Gross assets' of the Trust shall mean total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities or through the purchase of residual interest bonds), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles.

In addition to investing in residual interest bonds, the Trust may invest without limitation in other derivative instruments (which are instruments that derive their value from another instrument, security or index) acquired for hedging purposes. The Trust may purchase and sell various kinds of financial futures contracts and related options, including futures contracts and related options based on various debt securities and securities indices. The Trust also may enter into interest rate, total return and other swaps and forward rate contracts to seek to hedge against changes in interest rates or for other risk management purposes. See 'Investment Objectives, Policies and Risks - Additional Investment Practices - Derivative Instruments.'

During unusual market conditions, the Trust may invest up to 100% of its assets in cash or cash equivalents temporarily, which may be inconsistent with its investment objective(s) and other policies.

The foregoing credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event that a Rating Agency downgrades its assessment of the credit characteristics of a particular issue or withdraws its assessment. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance's assessment of the credit quality of the issuer of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies.

The Trust is a 'diversified' investment company which means that with respect to 75% of its total assets (1) it may not invest more than 5% of its total assets in the securities of any one issuer and (2) it may not own more than 10% of the outstanding voting securities of any one issuer. Therefore, with respect to no more than 25% of its total assets, the Trust may invest more than 5% of the value of its total assets in the obligations of any single issuer. To the extent the Trust invests a relatively high percentage of its assets in obligations of a limited number of issuers, the Trust will be more susceptible to any single corporate, economic, political or regulatory occurrence.

LISTING

As of July 20, 2021, The Trust had 15,396,359 Common Shares outstanding. The Trust's Common Shares are traded on the New York Stock Exchange ('NYSE') under the symbol 'EOT.' As of July 20, 2021, the last reported sale price of a Common Share of the Trust on the NYSE was $23.14. Any new Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

LEVERAGE

The Trust uses leverage in the form of residual interest bonds. The Trust will not utilize leverage in excess of 15% of its gross assets. Residual interest bonds are residual interests of a special purpose vehicle ('SPV') that holds municipal obligations. Residual interest bonds pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. The interest rate payable on a residual interest bond also bears an inverse relationship to the interest rate on floating rate notes issued by the SPV. Because changes in the interest rate on such floating rate notes inversely affect the interest paid on the residual interest bond, the value and income of a residual interest bond is generally more volatile than that of a fixed rate bond. Residual interest bonds have interest rate adjustment formulas that generally reduce or, in the extreme, eliminate the interest paid to the Trust when short-term interest rates rise, and increase the interest paid to the Trust when short-term interest rates fall. Residual interest bonds have varying degrees of liquidity, and the market for these securities is relatively volatile. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. Although volatile, residual interest bonds typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. While residual interest bonds expose the Trust to leverage risk because they provide two or more dollars of bond market exposure for every dollar invested, they are not subject to the Trust's restrictions on borrowings. See 'Investment Objectives, Policies and Risks' - Primary Investment Policies - Residual Interest Bonds.' Although the Trust has no current intention to do so, the Trust is also authorized to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act.

Eaton Vance National Municipal Opportunities Trust 8 Prospectus dated July 22,2021

Eaton Vance believes that the use of leverage (from residual interest bonds and any borrowings) may result in higher income to holders of Common Shares ('Common Shareholders') over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful.

The costs of the financial leverage program (from investment in residual interest bonds and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the NAV of Common Shares. The amount of fees paid to Eaton Vance for investment advisory services will be higher if the Trust uses financial leverage because the fees will be calculated based on the Trust's average daily gross assets, which may create a conflict of interest between Eaton Vance and the Common Shareholders. 'Gross assets' of the Trust means the total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage. See 'Investment Objectives, Policies and Risks - Risk Considerations - Leverage Risks.'

Financial leverage may also be achieved through the purchase of certain derivative instruments. The Trust's use of derivative instruments exposes the Trust to special risks. See 'Investment Objectives, Policies and Risks - Additional Investment Practices' and 'Investment Objectives, Policies and Risks - Additional Risk Considerations.'

INVESTMENT ADVISER AND ADMINISTRATOR

Eaton Vance is the Trust's investment adviser and administrator. Prior to March 1, 2021, Eaton Vance was a wholly owned subsidiary of Eaton Vance Corp. ('EVC'). On March 1, 2021, Morgan Stanley acquired EVC (the 'Transaction') and Eaton Vance became an indirect, wholly owned subsidiary of Morgan Stanley. As of March 31, 2021, Morgan Stanley's asset management operations had aggregate assets under management of approximately $1.4 trillion. See 'Management of the Trust.'

PLAN OF DISTRIBUTION

The Trust may sell the Common Shares being offered under this Prospectus in any one or more of the following ways: (i) directly to purchasers; (ii) through agents; (iii) to or through underwriters; or (iv) through dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale.

The Trust may distribute Common Shares from time to time in one or more transactions at: (i) a fixed price or prices that may be changed; (ii) market prices prevailing at the time of sale; (iii) prices related to prevailing market prices; or (iv) negotiated prices; provided, however, that in each case the offering price per Common Share (less any underwriting commission or discount) must equal or exceed the NAV per Common Share.

The Trust from time to time may offer its Common Shares through or to certain broker-dealers, including UBS Securities LLC, that have entered into selected dealer agreements relating to at-the-market offerings.

The Trust may directly solicit offers to purchase Common Shares, or the Trust may designate agents to solicit such offers. The Trust will, in a Prospectus Supplement relating to such Offering, name any agent that could be viewed as an underwriter under the 1933 Act, and describe any commissions the Trust must pay to such agent(s). Any such agent will be acting on a reasonable best efforts basis for the period of its appointment or, if indicated in the applicable Prospectus Supplement or other offering materials, on a firm commitment basis. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for the Trust in the ordinary course of business.

If any underwriters or agents are used in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will enter into an underwriting agreement or other agreement with them at the time of sale to them, and the Trust will set forth in the Prospectus Supplement relating to such Offering their names and the terms of the Trust's agreement with them.

If a dealer is utilized in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will sell such Common Shares to the dealer, as principal. The dealer may then resell such Common Shares to the public at varying prices to be determined by such dealer at the time of resale.

Eaton Vance National Municipal Opportunities Trust 9 Prospectus dated July 22,2021

The Trust may engage in at-the-market offerings to or through a market maker or into an existing trading market, on an exchange or otherwise, in accordance with Rule 415(a)(4) under the 1933 Act. An at-the-market offering may be through an underwriter or underwriters acting as principal or agent for the Trust.

Agents, underwriters and dealers may be entitled under agreements which they may enter into with the Trust to indemnification by the Trust against certain civil liabilities, including liabilities under the 1933 Act, and may be customers of, engage in transactions with or perform services for the Trust in the ordinary course of business.

In order to facilitate the Offering of Common Shares, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of Common Shares or any other Common Shares the prices of which may be used to determine payments on the Common Shares. Specifically, any underwriters may over-allot in connection with the Offering, creating a short position for their own accounts. In addition, to cover over-allotments or to stabilize the price of Common Shares or of any such other Common Shares, the underwriters may bid for, and purchase, Common Shares or any such other Common Shares in the open market. Finally, in any Offering of Common Shares through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing Common Shares in the Offering if the syndicate repurchases previously distributed Common Shares in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of Common Shares above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

The Trust may enter into derivative transactions with third parties, or sell Common Shares not covered by this Prospectus to third parties in privately negotiated transactions. If the applicable Prospectus Supplement indicates, in connection with those derivatives, the third parties may sell Common Shares covered by this Prospectus and the applicable Prospectus Supplement or other offering materials, including in short sale transactions. If so, the third parties may use Common Shares pledged by the Trust or borrowed from the Trust or others to settle those sales or to close out any related open borrowings of securities, and may use Common Shares received from the Trust in settlement of those derivatives to close out any related open borrowings of securities. The third parties in such sale transactions will be underwriters and, if not identified in this Prospectus, will be identified in the applicable Prospectus Supplement or other offering materials (or a post-effective amendment).

The maximum amount of compensation to be received by any member of the Financial Industry Regulatory Authority, Inc. will not exceed 8% of the initial gross proceeds from the sale of any security being sold with respect to each particular Offering of Common Shares made under a single Prospectus Supplement.

Any underwriter, agent or dealer utilized in the initial Offering of Common Shares will not confirm sales to accounts over which it exercises discretionary authority without the prior specific written approval of its customer.

DISTRIBUTIONS

The Trust intends to make regular monthly cash distributions to Common Shareholders. The amount of each monthly distribution will vary depending on a number of factors, including distributions payable on any preferred shares or other costs of financial leverage. As portfolio and market conditions change, the rate of distribution on the Common Shares and the Trust's distribution policy could change. Over time, the Trust will distribute all of its net investment income (after it pays accrued distributions on any outstanding preferred shares or other costs of financial leverage).

The net investment income of the Trust will consist of all interest income accrued on portfolio investments, short-term capital gain (including short-term gains on options, futures and forward positions and gains on the sale of portfolio investments held for one year or less) in excess of long-term capital loss and income from certain hedging transactions, less all expenses of the Trust. Expenses of the Trust will be accrued each day. Substantially all of the Trust's investment company taxable income will be distributed each year. In addition, at least annually, the Trust intends to distribute any net capital gain (which is the excess of net long-term capital gain over net short-term capital loss). To the extent that the Trust's net investment income and net capital gain for any year exceed the total monthly distributions paid during the year, the Trust will make a special distribution at or near year-end of such excess amount as may be required. If the Trust's total monthly distributions in any year exceed the amount of its net investment income and net capital gain for the year, any such excess would be characterized as a return of capital for federal income tax purposes. A return of capital is treated as a non-dividend distribution for tax purposes and is not subject to current tax. A return of capital reduces a Shareholder's tax cost basis in Trust shares. Under the 1940 Act, for any distribution that includes amounts from sources other than net income, the Trust is required to provide Common Shareholders a written statement regarding the components of such distribution. Such a statement will be provided at the time of any distribution believed to include any such amounts.

Common Shareholders may automatically reinvest some or all of their distributions in additional Common Shares pursuant to the Trust's dividend reinvestment plan. See 'Dividend Reinvestment Plan.'

Eaton Vance National Municipal Opportunities Trust 10 Prospectus dated July 22,2021

DIVIDEND REINVESTMENT PLAN

The Trust has established a dividend reinvestment plan (the 'Plan'). Under the Plan, unless a Common Shareholder elects to receive distributions in cash, all distributions will be automatically reinvested in additional Common Shares. American Stock Transfer & Trust Company, LLC ('AST' or the 'Plan Agent') serves as agent for the Common Shareholders in administering the Plan. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or, if the Common Shares are held in street or other nominee name, then to the nominee) by AST, as disbursing agent. Participation in the Plan is completely voluntary and may be terminated or resumed at any time without penalty by written notice if received by the Plan Agent prior to any distribution record date. See 'Dividend Reinvestment Plan.'

CLOSED-END STRUCTURE

Closed-end funds differ from open-end management investment companies (commonly referred to as mutual funds) in that closed-end funds generally list their shares for trading on a securities exchange and do not redeem their shares at the option of the shareholder. By comparison, mutual funds issue securities redeemable at NAV at the option of the shareholder and typically engage in a continuous offering of their shares. Mutual funds are subject to continuous asset in-flows and out-flows that can complicate portfolio management, whereas closed-end funds generally can stay more fully invested in securities consistent with the closed-end fund's investment objective(s) and policies. In addition, in comparison to open-end funds, closed-end funds have greater flexibility in the employment of financial leverage and in the ability to make certain types of investments, including investments in illiquid securities.

However, shares of closed-end funds frequently trade at a discount from their net asset value. Since inception, the market price of the Common Shares has fluctuated and at times traded below the Trust's NAV, and at times has traded above NAV. In recognition of the possibility that the Common Shares might trade at a discount to net asset value and that any such discount may not be in the interest of Common Shareholders, the Trust's Board of Trustees (the 'Board'), in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount. The Board might consider open market repurchases or tender offers for Common Shares at net asset value. There can be no assurance that the Board will decide to undertake any of these actions or that, if undertaken, such actions would result in the Common Shares trading at a price equal to or close to net asset value per Common Share. The Board might also consider the conversion of the Trust to an open-end management investment company. The Board believes, however, that the closed-end structure is desirable, given the Trust's investment objectives and policies. Investors should assume, therefore, that it is highly unlikely that the Board would vote to convert the Trust to an open-end management investment company.

SPECIAL RISK CONSIDERATIONS

Risk is inherent in all investing. Investing in any investment company security involves risk, including the risk that you may receive little or no return on your investment or even that you may lose part or all of your investment.

Discount From or Premium to NAV. The Offering will be conducted only when Common Shares of the Trust are trading at a price equal to or above the Trust's NAV per Common Share plus the per Common Share amount of commissions. As with any security, the market value of the Common Shares may increase or decrease from the amount initially paid for the Common Shares. The Trust's Common Shares have traded both at a premium and at a discount relative to net asset value. The shares of closed-end management investment companies frequently trade at a discount from their NAV. This is a risk separate and distinct from the risk that the Trust's NAV may decrease.

Secondary Market for the Common Shares. The issuance of Common Shares through the Offering may have an adverse effect on the secondary market for the Common Shares. The increase in the amount of the Trust's outstanding Common Shares resulting from the Offering may put downward pressure on the market price for the Common Shares of the Trust. Common Shares will not be issued pursuant to the Offering at any time when Common Shares are trading at a price lower than a price equal to the Trust's NAV per Common Share plus the per Common Share amount of commissions.

The Trust also issues Common Shares of the Trust through its dividend reinvestment plan. See 'Dividend Reinvestment Plan.' Common Shares may be issued under the plan at a discount to the market price for such Common Shares, which may put downward pressure on the market price for Common Shares of the Trust.

When the Common Shares are trading at a premium, the Trust may also issue Common Shares of the Trust that are sold through transactions effected on the NYSE. The increase in the amount of the Trust's outstanding Common Shares resulting from that offering may also put downward pressure on the market price for the Common Shares of the Trust.

Eaton Vance National Municipal Opportunities Trust 11 Prospectus dated July 22,2021

The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any future Common Share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if the Adviser is unable to invest the proceeds of such offering as intended, the Trust's per share distribution may decrease (or may consist of return of capital) and the Trust may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Investment and Market Risk. An investment in Common Shares is subject to investment risk, including the possible loss of the entire principal amount invested. An investment in Common Shares represents an indirect investment in the securities owned by the Trust, which will generally trade in the over-the-counter ('OTC') markets. The Common Shares at any point in time may be worth less than the original investment, even after taking into account any reinvestment of distributions.

Interest Rate and Income Risk. When interest rates decline, the value of municipal obligations held by the Trust can be expected to rise. Conversely, when interest rates rise, the value of municipal obligations held by the Trust can be expected to decline. Interest rate risk is the risk that the municipal obligations in the Trust's portfolio will decline in value because of increases in market interest rates. Generally, obligations with longer durations or maturities are more sensitive to changes in interest rates than obligations with shorter durations or maturities, causing them to be more volatile. Conversely, obligations with shorter durations or maturities will be less volatile but may provide lower returns than obligations with longer durations or maturities. A decline in the prices of the municipal obligations owned by the Trust would cause a decline in the NAV of the Trust, which could adversely affect the trading price of the Common Shares. The Trust may utilize certain strategies, including taking positions in futures or interest rate swaps and forward rate contracts, for the purpose of reducing the interest rate sensitivity of the portfolio and decreasing the Trust's exposure to interest rate risk, although there can be no assurance that it will do so or that such strategies will be successful.

Because the Trust is managed toward an income objective, it may hold more longer duration or maturity obligations and thereby be more exposed to interest rate risk than municipal income funds that are managed with a greater emphasis on total return. Certain factors, such as the presence of call features, may cause a particular fixed-income security, or the Trust as a whole, to exhibit less sensitivity to changes in interest rates. Certain of the Trust's investments may also be valued, in part, by reference to the relative relationship between interest rates on tax-exempt securities and taxable securities, respectively. When the market for tax-exempt securities underperforms (or outperforms) the market for taxable securities, the value of these investments may be negatively affected (or positively affected). Certain countries and regulatory bodies may use negative interest rates as a monetary policy tool to encourage economic growth during periods of deflation. In a negative interest rate environment, debt instruments may trade at negative yields, which means the purchaser of the instrument may receive at maturity less than the total amount invested.

The income investors receive from the Trust is based primarily on the interest it earns from its investments, which can vary widely over the short- and long-term. If long-term interest rates drop, investors' income from the Trust over time could drop as well if the Trust purchases securities with lower interest coupons.

The Trust invests in residual interest bonds. Compared to similar fixed-rate municipal bonds, the value of these bonds will fluctuate to a greater extent in response to changes in prevailing long-term interest rates. Moreover, the income earned on residual interest municipal bonds will fluctuate in response to changes in prevailing short-term interest rates. Thus, when such bonds are held by the Trust, an increase in short- or long-term market interest rates may adversely affect the income received from such bonds or the NAV of Trust shares.

Call and Reinvestment Risks. If interest rates fall, it is possible that issuers of callable bonds with high interest coupons will 'call' (or prepay) their bonds before their maturity date. If a call were exercised by the issuer during a period of declining interest rates, the Trust would likely replace such called security with a lower yielding security. If that were to happen, it could decrease the Trust's dividends and possibly could affect the market price of Common Shares. Similar risks exist when the Trust invests the proceeds from matured or traded municipal obligations at market interest rates that are below the Trust's current earnings rate.

Credit Risk. Credit risk is the risk that one or more municipal bonds in the Trust's portfolio will decline in price, or fail to pay interest or principal when due, because the issuer of the bond experiences a decline in its financial status. In general, lower rated municipal bonds carry a greater degree of risk that the issuer will lose its ability to make interest and principal payments, which could have a negative impact on the Trust's NAV or dividends. Securities rated in the fourth highest category (i.e., Baa by Moody's or BBB by S&P or Fitch) are considered investment grade quality, but may have speculative characteristics. Municipal obligations may be insured as to principal and interest payments. If the claims paying ability or other rating of the insurer is downgraded by a rating agency, the value of such obligations may be negatively affected. The Trust is also exposed to credit risk when it engages in certain types of derivatives transactions and when it engages in transactions that expose the Trust to counterparty risk. See 'Derivatives Risk.'

Eaton Vance National Municipal Opportunities Trust 12 Prospectus dated July 22,2021

Changes in the credit quality of the issuers of municipal obligations held by the Trust will affect the principal value of (and possibly the income earned on) such obligations. The credit quality of an issuer of municipal obligations may be affected by a variety of factors, including the issuer's tax base, the extent to which the issuer relies on federal or state aid, limitations on the taxing power of the issuer and changes in general economic conditions. Changes by Rating Agencies in their ratings of a security and in the ability of the issuer to make payments of principal and interest may also affect the value of the Trust's investments. The amount of information about the financial condition of an issuer of municipal obligations may not be as extensive as that made available by corporations whose securities are publicly traded.

In evaluating the quality of a particular instrument, Eaton Vance may take into consideration, among other things, a credit rating assigned by a credit rating agency, the issuer's financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. Credit rating agencies are private services that provide ratings of the credit quality of certain investments. Credit ratings issued by rating agencies are based on a number of factors including, but not limited to, the issuer's financial condition and the rating agency's credit analysis, if applicable, at the time of rating. As such, the rating assigned to any particular security is not necessarily a reflection of the issuer's current financial condition. The ratings assigned are not absolute standards of credit quality and do not evaluate market risks or necessarily reflect the issuer's current financial condition or the volatility or liquidity of the security.

For purposes of determining compliance with the Trust's credit quality restrictions, Eaton Vance relies primarily on the ratings assigned by credit rating agencies but may, in the case of unrated instruments, perform its own credit and investment analysis to determine an instrument's credit quality. A credit rating may have a modifier (such as plus, minus or a numerical modifier) to denote its relative status within the rating. The presence of a modifier does not change the security credit rating (for example, BBB- and Baa3 are within the investment grade rating) for purposes of the Trust's investment limitations. If an instrument is rated differently by two or more rating agencies, the highest rating will be used for purposes of the Trust's rating restrictions.

The Trust may invest in unrated obligations for which Eaton Vance will make a credit quality determination for purposes of the Trust's credit quality policy. To the extent that the Trust invests in such unrated obligations, the Trust's credit quality will be more dependent on Eaton Vance's credit analysis than if the Trust invested in only rated obligations.

The Trust may invest in municipal lease obligations ('MLOs') and certificates of participation. The obligation of the issuer to meet its obligations under such instruments is often subject to the ongoing appropriation by a legislative body, on an annual or other basis, of funds for the payment of the obligations. Investments in municipal leases are thus subject to the risk that the legislative body will not make the necessary appropriation and the issuer will not otherwise be willing or able to meet its obligation.

Liquidity Risk. The secondary market for some municipal obligations is less liquid than that for widely traded taxable debt obligations or widely traded municipal obligations. No established resale market exists for certain of the municipal obligations in which the Trust may invest. The Trust has no limitation on the amount of its assets that may be invested in securities that are not readily marketable or are subject to restrictions on resale. In certain situations, the Trust could find it more difficult to sell such securities at desirable times and/or prices. The Trust may not be able to readily dispose of such securities at prices that approximate those at which the Trust could sell such securities if they were more widely traded or at which the Trust has valued such securities and, as a result of such illiquidity, the Trust may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. In addition, the limited liquidity could affect the market price of the securities, thereby adversely affecting the Trust's NAV and ability to make distributions.

Municipal Bond Market Risk. Investing in the municipal bond market involves certain risks. Certain securities in which the Trust will invest will not be registered with the SEC or any state securities commission and will not be listed on any national securities exchange. The amount of public information available about the municipal obligations in the Trust's portfolio is generally less than for corporate equities or bonds, and the investment performance of the Trust may, therefore, be more dependent on the analytical abilities of Eaton Vance than if the Trust were a stock fund or taxable bond fund.

The ability of municipal issuers to make timely payments of interest and principal may be diminished during general economic downturns and as governmental cost burdens are reallocated among federal, state and local governments. In addition, laws enacted in the future by Congress or state legislatures or referenda could extend the time for payment of principal and/or interest, or impose other constraints on enforcement of such obligations, or on the ability of municipalities to levy taxes. Issuers of municipal obligations might seek protection under the bankruptcy laws. In the event of bankruptcy of an issuer, the Trust could experience delays in collecting principal and interest to which it is entitled, and may obtain only a limited recovery or no recovery in such circumstances. To enforce its rights in the event of default in the payment of interest or repayment of principal, or both, the Trust may take possession of and manage the assetssecuring the issuer's obligations on such securities, which may increase the Trust's operating expenses. Any income derived from the Trust's ownership or operation of such assets may not be tax-exempt.

Eaton Vance National Municipal Opportunities Trust 13 Prospectus dated July 22,2021

The value of municipal securities generally may be affected by uncertainties in the municipal markets as a result of legislation or litigation, including legislation or litigation that changes the taxation of municipal securities or the rights of municipal security holders in the event of a bankruptcy. Certain provisions of the U.S. Bankruptcy Code governing such bankruptcies are unclear. Further, the application of state law to municipal security issuers could produce varying results among the states or among municipal security issuers within a state. These uncertainties could have a significant impact on the prices of the municipal securities in which the Trust invests.

If the number of municipal borrowers and the amount of outstanding municipal securities contract, without corresponding reductions in investor demand for municipal securities, the Trust may have fewer investment alternatives, may invest in securities that it previously would have declined and may concentrate its investments in a smaller number of issuers.

Below Investment Grade Securities Risk. Up to 30% of the Trust's investments in municipal obligations may be, at the time of investment, rated below investment grade or if unrated deemed by the Adviser to be below investment grade. Such obligations are commonly called 'junk bonds' and will have speculative characteristics in varying degrees. While such obligations may have some quality and protective characteristics, these characteristics can be expected to be offset or outweighed by uncertainties or major risk exposures to adverse conditions.

Below investment grade municipal obligations involve a greater degree of credit, interest rate and market risk than investment grade municipal obligations. Below investment grade municipal obligations are subject to a greater risk of an issuer's inability to meet principal and interest payments on the obligations and may also be subject to greater price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity. Below investment grade municipal obligations are considered predominantly speculative because of the credit risk of their issuers. While offering a greater potential opportunity for capital appreciation and higher yields, below investment grade municipal obligations typically entail greater potential price volatility and may be less liquid than investment grade municipal obligations. Issuers of below investment grade municipal obligations are more likely to default on their payments of interest and principal owed to the Trust, and such defaults will reduce the Trust's NAV and income distributions. The prices of these below investment grade obligations are more sensitive to negative developments than higher rated securities. Adverse economic conditions generally lead to a higher non-payment rate. In addition, below investment grade municipal obligations may lose significant value before a default occurs as the market adjusts to expected higher non-payment rates.

Increases in interest rates and changes in the economy may adversely affect the ability of issuers of lower grade municipal obligations to pay interest and to repay principal, to meet projected financial goals and to obtain additional financing. Issuers of below investment grade municipal obligations may be more adversely affected by a prolonged recession or continued deterioration of economic conditions. In the event that an issuer of securities held by the Trust experiences difficulties in the timely payment of principal or interest and such issuer seeks to restructure the terms of its borrowings, the Trust may incur additional expenses and may determine to invest additional assets with respect to such issuer or the project or projects to which the Trust's portfolio securities relate. Further, the Trust may incur additional expenses to the extent that it is required to seek recovery upon a default in the payment of interest or the repayment of principal on its portfolio holdings, and the Trust may be unable to obtain full recovery thereof. When the Trust invests in lower rated or unrated municipal obligations, the achievement of the Trust's investment objectives is more dependent on the Adviser's credit analysis than would be the case if the Trust were investing in municipal obligations rated investment grade.

To the extent that there is no established market for some of the lower grade municipal obligations in which the Trust may invest, trading in such securities may be relatively inactive. The Adviser is responsible for determining the NAV of the Trust, subject to the supervision of the Trust's Board. During periods of reduced market liquidity and in the absence of readily available market quotations for lower grade municipal obligations held in the Trust's portfolio, the ability of the Adviser to value the Trust's securities becomes more difficult and the Adviser's use of judgment may play a greater role in the valuation of the Trust's securities due to the reduced availability of reliable objective data. The effects of adverse publicity and investor perceptions may be more pronounced for securities for which no established market exists as compared with the effects on securities for which a regular market does exist. Further, the Trust may have more difficulty selling such securities in a timely manner and at their stated value than would be the case for securities for which an established market does exist.

Municipal obligations held by the Trust that are initially rated below investment grade may subsequently be determined by the Adviser to be of investment grade quality for purposes of the Trust's investment policies if the securities subsequently are backed by escrow accounts containing U.S. Government obligations. The Trust may retain in its portfolio an obligation that declines in quality, including defaulted obligations, if such retention is considered desirable by the Adviser. In the case of a defaulted obligation, the Trust may incur additional expense seeking recovery of its investment.

Eaton Vance National Municipal Opportunities Trust 14 Prospectus dated July 22,2021

Insurance Risk. Municipal obligations may be insured as to their scheduled payment of principal and interest. Although the insurance feature may reduce some financial risks, the premiums for insurance and the higher market price sometimes paid for insured obligations may reduce the current yield on the insured obligation. Insured obligations also may be secured by bank credit agreements or escrow accounts. Changes in the ratings of an insurer may affect the value of an insured obligation, and in some cases may even cause the value of a security to be less than a comparable uninsured obligation. The insurance does not guarantee the market value of the insured obligation or the net asset value of the Trust's shares. If a municipal obligation is insured, the Trust will use the higher of the Municipal Obligation Rating or the insurance issuer's rating. The obligation of a municipal bond insurance company to pay a claim extends over the life of each insured obligation. Although defaults on insured municipal obligations have been low to date and municipal bond insurers have met their claims, there is no assurance this will continue. A higher than expected default rate could strain the insurer's loss reserves and adversely affect its ability to pay claims to bondholders. Because a significant portion of insured municipal obligations that have been issued and are outstanding is insured by a small number of insurance companies, an event involving one or more of these insurance companies, such as a credit rating downgrade, could have a significant adverse effect on the value of the municipal obligations insured by that insurance company and on the municipal bond markets as a whole.

Current Regulatory Environment Risk. From time to time proposals have been introduced before Congress for the purpose of restricting or eliminating the federal income tax exemption for interest on certain types of municipal obligations, and it can be expected that similar proposals may be introduced in the future. Any proposed or actual changes in such rates or exempt status, therefore, can significantly affect the demand for and supply, liquidity and marketability of municipal obligations. This could in turn affect the Trust's net asset value and ability to acquire and dispose of municipal obligations at desirable yield and price levels.

The U.S. and non-U.S. derivatives markets have undergone substantial changes in recent years as a result of changes under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the 'Dodd-Frank Act') in the United States and regulation changes in Europe, Asia and other non-U.S. jurisdictions. In particular, the Dodd-Frank Act and related regulations require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. Additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Trust engages in derivative transactions. Trust management cannot predict the effects of any new governmental regulation that may be implemented, and future regulation may impair the effectiveness of the Trust's derivative transactions and its ability to achieve its investment objectives.

At any time after the date of this prospectus, legislation may be enacted that could negatively affect the assets of the Trust. Legislation or regulation may change the way in which the Trust itself is regulated. The Adviser cannot predict the effects of any new governmental regulation that may be implemented, and there can be no assurance that any new governmental regulation will not adversely affect the Trust's ability to achieve its investment objectives.

State Specific Risk. If the Trust focuses its investments in any one state (or U.S. territory), the Trust may be more susceptible to adverse economic, political or regulatory occurrences affecting a particular state (or territory). Certain municipal bond issuers in Puerto Rico have recently experienced financial difficulties and rating agency downgrades, and two such issuers have defaulted on their payment obligations.

Up to 5% of the Trust's investments in municipal obligations may be collateralized by the proceeds from class action or other litigation against the tobacco industry. Such municipal obligations are backed solely by expected revenues to be derived from lawsuits involving tobacco-related deaths and illnesses which were settled between certain states and American tobacco companies. Tobacco settlement bonds are secured by an issuing state's proportionate share in the Master Settlement Agreement ('MSA'). The MSA is an agreement, reached out of court in November 1998 between 46 states and nearly all of the major U.S. tobacco manufacturers. Under the terms of the MSA, the actual amount of future settlement payments by tobacco manufacturers is dependent on many factors, including, but not limited to, annual domestic cigarette shipments, reduced cigarette consumption, increased taxes on cigarettes, inflation, financial capability of tobacco companies, continuing litigation and the possibility of tobacco manufacturer bankruptcy. Payments made by tobacco manufacturers could be negatively impacted if the decrease in tobacco consumption is significantly greater than the forecasted decline. See 'State Specific Investments' in the SAI for additional information about tobacco settlement bonds and the MSA.

Residual Interest Bond Risk. Residual interest bonds are residual interests of a SPV that holds municipal obligations. Residual interest bonds pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. The interest rate payable on a residual interest bond also bears an inverse relationship to the interest rate on floating rate notes issued by the SPV ('Floating Rate Notes'). Because changes in the interest rate on the Floating Rate Notes inversely affect the interest paid on the residual interest bond, the value and

Eaton Vance National Municipal Opportunities Trust 15 Prospectus dated July 22,2021

income of a residual interest bond is generally more volatile than that of a fixed rate bond. Residual interest bonds have interest rate adjustment formulas that generally reduce or, in the extreme, eliminate the interest paid to the Trust when short-term interest rates rise, and increase the interest paid to the Trust when short-term interest rates fall. Residual interest bonds have varying degrees of liquidity, and the market for these securities is relatively volatile. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. Although volatile, residual interest bonds typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. These securities usually permit the investor to convert the floating rate to a fixed rate (normally adjusted downward), and this optional conversion feature may provide a partial hedge against rising rates if exercised at an opportune time. While residual interest bonds expose the Trust to leverage risk because they provide two or more dollars of bond market exposure for every dollar invested, they are not subject to the Trust's restrictions on borrowings.

Any economic effect of leverage through the Trust's purchase of residual interest bonds will create an opportunity for increased Common Share net income and returns, but will also create the possibility that the Trust's long-term returns will be diminished if the cost of leverage exceeds the return on the bonds purchased with leverage by the Trust. The amount of fees paid to Eaton Vance for investment advisory services will be higher if the Trust uses financial leverage because the fees will be calculated based on the Trust's average daily gross assets, which may create a conflict of interest between Eaton Vance and the Common Shareholders. 'Gross assets' of the Trust means the total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage. See 'Investment Objectives, Policies and Risks - Risk Considerations - Leverage Risk.'

A SPV typically can be collapsed or closed by the holder of the residual interest bonds (such as the Trust) or by the liquidity provider. In certain circumstances, the Trust may enter into shortfall and forbearance agreements with respect to a residual interest bond. The Trust generally may enter into such agreements (i) when the liquidity provider to the SPV requires such an agreement because the level of leverage in the SPV exceeds the level that the liquidity provider is willing support absent such an agreement; and/or (ii) to seek to prevent the liquidity provider from collapsing the SPV in the event that the municipal obligation held in the SPV has declined in value. Such agreements commit the Trust to reimburse, upon the termination of the SPV issuing the inverse floater, the difference between the liquidation value of the underlying security (which is the basis of the inverse floater) and the principal amount due to the holders of the floating rate security issued in conjunction with the inverse floater. Such agreements may expose a Trust's other assets to losses. Absent a shortfall and forbearance agreement, the Trust would not be required to make such a reimbursement. If the Trust chooses not to enter into such an agreement, the inverse floater could be terminated and the Trust could incur a loss. Consistent with SEC staff guidance, the Trust will segregate or earmark liquid assets with its custodian on a mark-to-market basis to cover any such payment obligations to liquidity providers.

On December 10, 2013, five U.S. federal agencies published final rules implementing section 619 of the Dodd-Frank Wall Street Reform and Consumer Protection Act (the 'Volcker Rule'). The Volcker Rule prohibits banking entities from engaging in proprietary trading of certain instruments and limits such entities' investments in, and relationships with, covered funds, as defined in the rules. The Volcker Rule precludes banking entities and their affiliates from (i) sponsoring residual interest bond programs as presently structured and (ii) continuing relationships with or services for existing residual interest bond programs. The effects of the Volcker Rule may make it more difficult for the Trust to maintain current or desired levels of income.

Risks of MLOs and Certificates of Participation. The Trust may invest in MLOs and certificates of participation that involve special risks not normally associated with general obligations or revenue obligations. A MLO is a bond that is secured by lease payments made by the party, typically a state or municipality, leasing the facilities (e.g., schools or office buildings) that were financed by the bond. Such lease payments may be subject to annual appropriation or may be made only from revenues associated with the facility financed. In other cases, the leasing state or municipality is obligated to appropriate funds from its general tax revenues to make lease payments as long as it utilizes the leased property. A certificate of participation (also referred to as a 'participation') in a municipal lease is an instrument evidencing a pro rata share in a specific pledged revenue stream, usually lease payments by the issuer . The issuer's obligations under such instruments are often subject to the ongoing appropriation by a legislative body, on an annual or other basis, of funds for the payment thereof. Investments in MLOs and certificates of participation are therefore typically subject to the risk that the legislative body will not make the necessary annual appropriation and the issuer will not otherwise be willing or able to meet its obligation.

Inflation Risk/Deflation Risk. Inflation risk is the risk that the value of assets or income from investment will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Common Shares and distributions thereon can decline. In addition, during periods of rising inflation, short-term interest rates and the Trust's cost of leverage would likely increase, reducing returns to Common Shareholders to the extent that such increased cost is not offset by commensurately higher income. Deflation risk is the risk that prices throughout the economy decline over time − the opposite of inflation. Deflation may have an adverse affect on the creditworthiness of issuers and may make issuer defaults more likely, which may result in a decline in the value of the Trust's investments.

Eaton Vance National Municipal Opportunities Trust 16 Prospectus dated July 22,2021

Leverage Risk. The Trust will not utilize leverage in excess of 15% of its gross assets. As discussed above, the Trust currently uses leverage created by investing in residual interest bonds. The Trust will comply with the asset segregation requirements of the 1940 Act in making such investments. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term interest rates and provide the economic effect of leverage. Although the Trust has no current intention to do so, the Trust is authorized to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act. There can be no assurance a leveraging strategy will be successful during any period in which it is employed.

The Adviser anticipates that the use of leverage (from residual interest bonds) may result in higher income to Common Shareholders over time. Leverage creates risks for Common Shareholders, including the likelihood of greater volatility of NAV and market price of the Common Shares and the risk that fluctuations in the costs of leverage may affect the return to Common Shareholders. To the extent the income derived from investments purchased with funds received from leverage exceeds the cost of leverage, the Trust's distributions will be greater than if leverage had not been used. Conversely, if the income from the investments purchased with such funds is not sufficient to cover the cost of leverage, the amount available for distribution to Common Shareholders will be less than if leverage had not been used. In the latter case, Eaton Vance, in its best judgment, may nevertheless determine to maintain the Trust's leveraged position if it deems such action to be appropriate. There can be no assurance that a leveraging strategy will be successful.

As discussed under 'Management of the Trust,' the investment advisory fee paid to Eaton Vance is calculated on the basis of the Trust's average daily gross assets. 'Gross assets' of the Trust shall mean total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. This means that the Trust's advisory fees will be higher when leverage is utilized which may create an incentive for the Adviser to employ leverage. In this regard, holders of any preferred shares do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds of the use of leverage, which means that Common Shareholders effectively bear the entire advisory fee.

Financial leverage may also be achieved through the purchase of certain derivative instruments. The Trust's use of derivative instruments exposes the Trust to special risks. See 'Investment Objectives, Policies and Risks - Additional Investment Practices' and 'Investment Objectives, Policies and Risks - Additional Risk Considerations.'

Derivatives Risk. In addition to investing in residual interest bonds, the Trust may invest without limitation in other derivative instruments (which are instruments that derive their value from a reference instrument) acquired for hedging purposes or investment purposes, such as financial futures contracts and related options, interest rate, total return and other swaps and forward rate contracts. Depending on the type of derivative instrument and the Trust's investment strategy, a reference instrument could be a security, instrument, index, currency, commodity, economic indicator or event ('reference instruments'). The loss on derivative instruments (other than purchased options) may substantially exceed amounts invested in these instruments. Derivative transactions, including options on securities and securities indices and other transactions in which the Trust may invest may subject the Trust to increased risk of principal loss due to unexpected movements in securities prices and interest rates, and imperfect correlations between the Trust's securities holdings and indices upon which derivative transactions are based. Derivatives can be illiquid, may disproportionately increase losses, and may have a potentially large impact on the Trust's performance. Use of derivative instruments may cause the realization of higher amounts of short-term capital gains (generally taxed at ordinary income tax rates) than if such instruments had not been used. Trust obligations created pursuant to derivative instruments may give rise to leverage, which would subject the Trust to increased leverage risk. The Trust also will be subject to credit risk with respect to the counterparties to any OTC derivatives contracts entered into by the Trust. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Trust may experience significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Trust may obtain only a limited recovery or no recovery in such circumstances.

The use of derivatives to enhance income is considered to be speculative in nature. The use of derivatives may result in greater losses than if they had not been used, may require the Trust to sell or purchase portfolio investments at inopportune times or for prices other than current market value, may limit the amount of appreciation the Trust can realize on an investment or may cause the Trust to hold a security it might otherwise sell. Segregated liquid assets, amounts paid by the Trust as premiums and cash or other assets held in margin accounts with respect to derivatives transactions are not otherwise available to the Trust for investment or operational purposes. Certain derivative transactions may have economic characteristics similar to leverage. See 'Additional Risk Considerations - Leverage Risk.'

Eaton Vance National Municipal Opportunities Trust 17 Prospectus dated July 22,2021

The U.S. and non-U.S. derivatives markets have undergone substantial changes in recent years as a result of changes under the Dodd-Frank Act in the United States and regulation changes in Europe, Asia and other non-U.S. jurisdictions. In particular, the Dodd-Frank Act and related regulations require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. As of October 28, 2020, the SEC has adopted new regulations that may significantly alter the Trust's regulatory obligations with regard to its derivatives usage. In particular, the new regulations will, upon implementation, eliminate the current asset segregation framework for covering derivatives and certain other financial instruments, impose new responsibilities on the Board and establish new reporting and recordkeeping requirements for the Trust and may, depending on the extent to which the Trust uses derivatives, impose value at risk limitations on the Trust's use of derivatives, and require the Trust's Board to adopt a derivative risk management program. The implementation of these requirements may limit the ability of the Trust to use derivative instruments as part of its investment strategy, increase the costs of using these instruments or make them less effective. Additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Trust engages in derivative transactions. Trust management cannot predict the effects of any new governmental regulation that may be implemented, and there can be no assurance that any new government regulation will not adversely affect the Trust's performance or ability to achieve its investment objectives.

Counterparty Risk. Changes in the credit quality of the companies that serve as the Trust's counterparties with respect to its derivatives positions and liquidity providers for the Trust's residual interest bonds or other investments supported by another party's credit will affect the value of those instruments. Certain entities that have served as counterparties in the municipals markets have in the past incurred significant financial hardships, including bankruptcy and material loss of credit standing as a result of exposure to investments that have experienced defaults or otherwise suffered extreme credit deterioration. As a result, such hardships reduced these entities' capital and called into question their continued ability to perform their obligations. By using derivatives or other instruments that expose the Trust to counterparties, the Trust assumes the risk that its counterparties could experience future financial hardship.

The counterparty risk for cleared derivatives is generally lower than for uncleared over-the-counter derivative transactions since generally a clearing organization becomes substituted for each counterparty to a cleared derivative contract and, in effect, guarantees the parties' performance under the contract as each party to a trade looks only to the clearing organization for performance of financial obligations under the derivative contract. However, there can be no assurance that a clearing organization, or its members, will satisfy its obligations to the Trust.

Tax Risk. The value of the Trust's investments and its NAV may be adversely affected by changes in tax rates and policies. Because interest income from municipal obligations normally is not subject to regular federal income taxation, the attractiveness of municipal obligations in relation to other investment alternatives is affected by changes in federal income tax rates or changes in the tax-exempt status of interest income from municipal obligations. From time to time proposals have been introduced before Congress for the purpose of restricting or eliminating the federal income tax exemption for interest on certain types of municipal obligations, and it can be expected that similar proposals may be introduced in the future. Any proposed or actual changes in such rates or exempt status, therefore, can significantly affect the demand for and supply, liquidity and marketability of municipal obligations. This could, in turn, affect the Trust's NAV and ability to acquire and dispose of municipal obligations at desirable yield and price levels. The Trust is not a suitable investment for individual retirement accounts, for other tax-exempt or tax-deferred accounts or for investors who are otherwise indifferent to the federal income tax consequences of their investments. See 'Distributions' and 'Federal income tax matters.'

The Trust will invest in municipal obligations in reliance at the time of purchase on an opinion of bond counsel to the issuer that the interest paid on those securities will be excludable from gross income under the regular federal income tax, and the Adviser will typically not independently verify that opinion. Subsequent to the Trust's acquisition of such a municipal security, however, the security may be determined to pay, or to have paid, taxable income. As a result, the treatment of dividends previously paid or to be paid by the Trust as 'exempt-interest dividends' could be adversely affected, subjecting the Trust's Common Shareholders to increased federal income tax liabilities.

Interest income from certain types of municipal obligations may be a tax preference item for purposes of the AMT for individual investors.

Eaton Vance National Municipal Opportunities Trust 18 Prospectus dated July 22,2021

Futures Risk. Although some futures contracts call for making or taking delivery of the underlying reference instrument, generally these obligations are closed out prior to delivery by offsetting purchases or sales of matching futures contracts (same exchange, underlying security or index, and delivery month). Closing a futures contract sale is effected by purchasing a futures contract for the same aggregate amount of the specific type of financial instrument or commodity with the same delivery date. If an offsetting purchase price is less than the original sale price, the Trust realizes a capital gain, or if it is more, the Trust realizes a capital loss. Conversely, if an offsetting sale price is more than the original purchase price, the Trust realizes a capital gain, or if it is less, the Trust realizes a capital loss. The Adviser has claimed an exclusion from the definition of a Commodity Pool Operator ('CPO') under the Commodity Exchange Act with respect to the Trust and therefore, neither the Adviser nor the Trust are subject to registration or regulation thereunder.

Management Risk. The Trust is subject to management risk because it is actively managed. Eaton Vance and the individual portfolio managers invest the assets of the Trust as they deem appropriate in implementing the Trust's investment strategy. Accordingly, the success of the Trust depends upon the investment skills and analytical abilities of Eaton Vance and the individual portfolio managers to develop and effectively implement strategies that achieve the Trust's investment objectives. There is no assurance that Eaton Vance and the individual portfolio managers will be successful in developing and implementing the Trust's investment strategy. Subjective decisions made by Eaton Vance and the individual portfolio managers may cause the Trust to incur losses or to miss profit opportunities.

Recent Market Conditions. An outbreak of respiratory disease caused by a novel coronavirus was first detected in China in late 2019 and subsequently spread internationally. This coronavirus has resulted in closing borders, enhanced health screenings, changes to healthcare service preparation and delivery, quarantines, cancellations, disruptions to supply chains and customer activity, as well as general concern and uncertainty. The impact of this coronavirus has resulted in a substantial economic downturn, which may continue for an extended period of time. Health crises caused by outbreaks of disease, such as the coronavirus outbreak, may exacerbate other pre-existing political, social and economic risks and disrupt normal market conditions and operations. The impact of this outbreak has negatively affected the worldwide economy, as well as the economies of individual countries and industries, and could continue to affect the market in significant and unforeseen ways. Other epidemics and pandemics that may arise in the future may have similar effects. For example, a global pandemic or other widespread health crisis could cause substantial market volatility and exchange trading suspensions and closures. In addition, the increasing interconnectedness of markets around the world may result in many markets being affected by events or conditions in a single country or region or events affecting a single or small number of issuers. The coronavirus outbreak and public and private sector responses thereto have led to large portions of the populations of many countries working from home for indefinite periods of time, temporary or permanent layoffs, disruptions in supply chains, and lack of availability of certain goods. The impact of such responses could adversely affect the information technology and operational systems upon which the Trust and the Trust's service providers rely, and could otherwise disrupt the ability of the employees of the Trust's service providers to perform critical tasks relating to the Trust. Any such impact could adversely affect the Trust's performance, or the performance of the securities in which the Trust invests and may lead to losses on your investment in the Trust.

Cybersecurity Risk. With the increased use of technologies by Trust service providers to conduct business, such as the Internet, the Trust is susceptible to operational, information security and related risks. The Trust relies on communications technology, systems, and networks to engage with clients, employees, accounts, shareholders, and service providers, and a cyber incident may inhibit the Trust's ability to use these technologies. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber attacks include, but are not limited to, gaining unauthorized access to digital systems (e.g., through 'hacking' or malicious software coding) for purposes of misappropriating assets or sensitive information, corrupting data, or causing operational disruption. Cyber attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites. A denial-of-service attack is an effort to make network services unavailable to intended users, which could cause shareholders to lose access to their electronic accounts, potentially indefinitely. Employees and service providers also may not be able to access electronic systems to perform critical duties for the Trust, such as trading and NAV calculation, during a denial-of-service attack. There is also the possibility for systems failures due to malfunctions, user error and misconduct by employees and agents, natural disasters, or other foreseeable and unforeseeable events.

Because technology is consistently changing, new ways to carry out cyber attacks are always developing. Therefore, there is a chance that some risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the Trust's ability to plan for or respond to a cyber attack. Like other Trusts and business enterprises, the Trust and its service providers have experienced, and will continue to experience, cyber incidents consistently. In addition to deliberate cyber attacks, unintentional cyber incidents can occur, such as the inadvertent release of confidential information by the Trust or its service providers.

Eaton Vance National Municipal Opportunities Trust 19 Prospectus dated July 22,2021

The Trust uses third party service providers who are also heavily dependent on computers and technology for their operations. Cybersecurity failures or breaches by the Trust's investment adviser or administrator and other service providers (including, but not limited to, the custodian or transfer agent), and the issuers of securities in which the Trust invests, may disrupt and otherwise adversely affect their business operations. This may result in financial losses to the Trust, impede Trust trading, interfere with the Trust's ability to calculate its NAV, or cause violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, litigation costs, or additional compliance costs. While many of the Trust service providers have established business continuity plans and risk management systems intended to identify and mitigate cyber attacks, there are inherent limitations in such plans and systems including the possibility that certain risks have not been identified. The Trust cannot control the cybersecurity plans and systems put in place by service providers to the Trust and issuers in which the Trust invests. The Trust and its shareholders could be negatively impacted as a result.

Other Investment Companies Risk. The Trust may, subject to the limitations of the 1940 Act, invest in the securities of other investment companies. Such securities may be leveraged. As a result, the Trust may be indirectly exposed to leverage through an investment in such securities. Utilization of leverage is a speculative investment technique and involves certain risks. The Trust, as a holder of the securities of other investment companies, will bear its pro rata portion of the other investment companies' expenses, including advisory fees. These expenses are in addition to the direct expenses of the Trust's own operations.

Market Disruption. Global instability, war, geopolitical tensions and terrorist attacks in the United States and around the world have previously resulted, and may in the future result in market volatility and may have long-term effects on the United States and worldwide financial markets and may cause further economic uncertainties in the United States and worldwide. The Trust cannot predict the effects of significant future events on the global economy and securities markets. A similar disruption of the financial markets could impact interest rates, auctions, secondary trading, ratings, credit risk, inflation and other factors relating to the Common Shares.

Swaps Risk. Swap agreements are two-party contracts entered into primarily by institutional investors for periods ranging from a few weeks to more than one year. In a standard 'swap' transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on a particular predetermined reference instrument or instruments, which can be adjusted for an interest rate factor. The gross returns to be exchanged or 'swapped' between the parties are generally calculated with respect to a 'notional amount' (i.e., the return on or increase in value of a particular dollar amount invested at a particular interest rate or in a 'basket' of securities representing a particular index). Other types of swap agreements may calculate the obligations of the parties to the agreement on a 'net basis.' Consequently, a party's current obligations (or rights) under a swap agreement will generally be equal only to the net amount to be paid or received under the agreement based on the relative values of the positions held by each party to the agreement (the 'net amount'). Whether the use of swap agreements will be successful will depend on the Adviser's ability to predict correctly whether certain types of reference instruments are likely to produce greater returns than other instruments. Swap agreements may be subject to contractual restrictions on transferability and termination and they may have terms of greater than seven days. The Trust's obligations under a swap agreement will be accrued daily (offset against any amounts owed to the Trust under the swap). Developments in the swaps market, including potential government regulation, could adversely affect the Trust's ability to terminate existing swap agreements or to realize amounts to be received under such agreements, as well as to participate in swap agreements in the future. If there is a default by the counterparty to a swap, the Trust will have contractual remedies pursuant to the swap agreement, but any recovery may be delayed depending on the circumstances of the default.

Duration and Maturity Risk. Holding long duration and long maturity investments will expose the Trust to certain magnified risks. These risks include interest rate risk, credit risk and liquidity risks as discussed above.

Hedging Risk. The Trust's use of derivatives or other transactions to reduce risks involves costs and will be subject to Eaton Vance's ability to predict correctly changes in the relationships of such hedge instruments to the Trust's portfolio holdings or other factors. No assurance can be given that Eaton Vance's judgment in this respect will be correct. In addition, no assurance can be given that the Trust will enter into hedging or other transactions at times or under circumstances in which it may be advisable to do so. Hedging transactions have risks, including the imperfect correlation between the value of such instruments and the underlying assets of the Trust, which creates the possibility that the loss on such instruments may be greater than the gain, if any, in the value of the underlying asset in the Trust's portfolio; the limited availability of such instruments; the loss of principal; the possible default of the other party to the transaction; illiquidity of the derivative investments; and the imperfect correlation between the tax-exempt and taxable markets. Furthermore, the ability to successfully use hedging transactions depends on the Eaton Vance's ability to predict pertinent market movements, which cannot be assured. Thus, the use of hedging transactions may result in losses greater than if they had not been used, may require the Trust to sell or purchase portfolio investments at inopportune times or for prices other than current market values, may limit the amount of appreciation the Trust can realize on an investment, or may cause the Trust to hold a security that it might otherwise sell.

Eaton Vance National Municipal Opportunities Trust 20 Prospectus dated July 22,2021

Anti-takeover Provisions. The Trust's Agreement and Declaration of Trust (the 'Declaration of Trust') and Amended and Restated By-Laws (the 'By-Laws' and together with the Declaration of Trust, the 'Organizational Documents') include provisions that could have the effect of limiting the ability of other persons or entities to acquire control of the Trust or to change the composition of its Board. For example, pursuant to the Trust's Declaration of Trust, the Board is divided into three classes of Trustees with each class serving for a three-year term and certain types of transactions require the favorable vote of holders of at least 75% of the outstanding shares of the Trust. See 'Description of Capital Structure - Certain Provisions of the Organizational Documents - Anti-Takeover Provisions in the Organizational Documents.'

Summary of Trust Expenses

The purpose of the table below is to help you understand all fees and expenses that you, as a Common Shareholder, would bear directly or indirectly. The table reflects leverage attributable to floating-rate notes for the fiscal year ended March 31, 2021 in an amount equal to 6.10% of the Trust's gross assets (including floating-rate notes) and shows Trust expenses as a percentage of net assets attributable to Common Shares.

Common Shareholder transaction expenses
Sales Load paid by you (as a percentage of offering price) --(1)
Offering expenses (as a percentage of offering price) None(2)
Dividend reinvestment plan fees $5.00(3)
Annual expenses

Percentage of net assets
attributable to Common Shares(4)

Investment advisory fee 0.64%(5)
Interest expenses 0.05%(6)
Other expenses 0.09%
Total annual Trust operating expenses 0.78%
(1) If Common Shares are sold to or through underwriters, the prospectus supplement will set forth any applicable sales load.
(2) The Adviser will pay the expenses of the Offering (other than the applicable commissions); therefore, Offering expenses are not included in the Summary of Trust Expenses. Offering expenses generally include, but are not limited to, the preparation, review and filing with the SEC of the Trust's registration statement (including this Prospectus and the SAI), the preparation, review and filing of any associated marketing or similar materials, costs associated with the printing, mailing or other distribution of the Prospectus, SAI and/or marketing materials, associated filing fees, NYSE listing fees, and legal and auditing fees associated with the Offering.
(3) You will be charged a $5.00 service charge and pay brokerage charges if you direct the plan agent to sell your Common Shares held in a dividend reinvestment account.
(4) Stated as a percentage of average net assets attributed to Common Shares for the year ended March 31, 2021.
(5) The advisory fee paid by the Trust to the Adviser is based on the average daily gross assets of the Trust, including all assets attributable to any form of investment leverage that the Trust may utilize. Accordingly, if the Trust were to increase investment leverage in the future, the advisory fee will increase as a percentage of net assets.
(6) 'Interest Expenses' relate to the Trust's liability with respect to floating-rate notes held by third parties in conjunction with investments in residual interest bonds. The Trust records offsetting interest income in an amount at least equal to this expense relating to the municipal obligations underlying such transactions.

EXAMPLE

The following example illustrates the expenses that Common Shareholders would pay on a $1,000 investment in Common Shares, assuming (i) total annual Trust operating expenses of 0.78% of net assets attributable to Common Shares in years 1 through 10; (ii) a 5% annual return; and (iii) all distributions are reinvested at NAV:

1 Year 3 Years 5 Years 10 Years
$8 $25 $43 $97

The above table and example and the assumption in the example of a 5% annual return are required by regulations of the SEC that are applicable to all investment companies; the assumed 5% annual return is not a prediction of, and does not represent, the projected or actual performance of the Trust's Common Shares. For more complete descriptions of certain of the Trust's costs and expenses, see 'Management of the Trust.' In addition, while the example assumes reinvestment of all dividends and distributions at NAV, participants in the Trust's dividend reinvestment plan may receive Common Shares purchased or issued at a price or value different from NAV. See 'Distributions' and 'Dividend Reinvestment Plan.' The example does not include sales load or estimated offering costs, which would cause the expenses shown in the example to increase.

The example should not be considered a representation of future expenses. Actual expenses may be higher or lower. The Trust's actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

Eaton Vance National Municipal Opportunities Trust 21 Prospectus dated July 22,2021

Financial Highlights and Investment Performance

FINANCIAL HIGHLIGHTS

This table details the financial performance of the Common Shares, including total return information showing how much an investment in the Trust has increased or decreased each period. This information has been audited by Deloitte & Touche LLP, an independent registered public accounting firm. The report of Deloitte & Touche LLP and the Trust's financial statements are incorporated by reference and included in the Trust's annual report, which is available upon request.

Selected data for a Common Share outstanding during the periods stated.

Year Ended March 31,
2021 2020 2019 2018 2017
Net asset value - Beginning of year $ 20.530 $ 21.090 $ 21.320 $ 21.700 $ 22.890
Income (Loss) From Operations
Net investment income(1) $ 0.780 $ 0.835 $ 0.955 $ 0.986 $ 1.016
Net realized and unrealized gain (loss) 1.183 (0.412) (0.057) (0.213) (0.969)
Total income from operations $ 1.963 $ 0.423 $ 0.898 $ 0.773 $ 0.047
Less Distributions
From net investment income $ (0.764) $ (0.841) $ (1.021) $ (1.031) $ (1.030)
From net realized gain - (0.078) (0.107) (0.122) (0.207)
Tax return of capital - (0.065) - - -
Total distributions $ (0.764) $ (0.984) $ (1.128) $ (1.153) $ (1.237)
Premium from common shares sold through shelf offering(1) $ 0.001 $ 0.001 $ - $ - $ -
Net asset value - End of year $ 21.730 $ 20.530 $ 21.090 $ 21.320 $ 21.700
Market value - End of year $ 22.500 $ 19.500 $ 21.120 $ 20.670 $ 21.520
Total Investment Return on Net Asset Value(2) 9.87% 1.90% 4.54% 3.59% 0.29%
Total Investment Return on Market Value(2) 19.77% (3.35)% 7.98% 1.27% 2.04%
Ratios/Supplemental Data
Net assets, end of year (000's omitted) $ 333,178 $ 314,321 $ 321,241 $ 324,587 $ 330,183
Ratios (as a percentage of average daily net assets):
Expenses excluding interest and fees 0.73% 0.75% 0.76% 0.76% 0.75%
Interest and fee expense(4) 0.05% 0.17% 0.22% 0.20% 0.16%
Total expenses 0.78% 0.92% 0.98% 0.96% 0.91%
Net investment income 3.67% 3.88% 4.55% 4.52% 4.50%
Portfolio Turnover 13% 44% 17% 17% 11%

(See related footnotes.)

Eaton Vance National Municipal Opportunities Trust 22 Prospectus dated July 22,2021

Financial Highlights (continued)

Year Ended March 31,
2016 2015 2014 2013 2012
Net asset value - Beginning of year $ 23.050 $ 21.510 $ 22.700 $ 21.640 $ 19.320
Income (Loss) From Operations
Net investment income(1) $ 1.065 $ 1.087 $ 1.096 $ 1.106 $ 1.174
Net realized and unrealized gain (loss) (0.190) 1.479 (1.270) 1.029 2.309
Total income (loss) from operations $ 0.875 $ 2.566 $ (0.174) $ 2.135 $ 3.483
Less Distributions
From net investment income $ (1.030) $ (1.030) $ (1.030) $ (1.075) $ (1.163)
From net realized gain (0.005) - - - -
Total distributions $ (1.035) $ (1.030) $ (1.030) $ (1.075) $ (1.163)
Anti-dilutive effect of share repurchase program(1) $ - $ 0.004 $ 0.014 $ - $ -
Net asset value - End of year $ 22.890 $ 23.050 $ 21.510 $ 22.700 $ 21.640
Market value - End of year $ 22.310 $ 21.200 $ 19.390 $ 22.250 $ 21.800
Total Investment Return on Net Asset Value(2) 4.27% 12.68% (0.02)% 10.03% 18.67%
Total Investment Return on Market Value(2) 10.50% 14.96% (8.05)% 7.06% 23.98%
Ratios/Supplemental Data
Net assets, end of year (000's omitted) $ 348,145 $ 350,611 $ 327,723 $ 347,887 $ 331,234
Ratios (as a percentage of average daily net assets):
Expenses excluding interest and fees(3) 0.76% 0.77% 0.79% 0.78% 0.80%
Interest and fee expense(4) 0.08% 0.09% 0.11% 0.10% 0.11%
Total expenses(3) 0.84% 0.86% 0.90% 0.88% 0.91%
Net investment income 4.70% 4.83% 5.17% 4.90% 5.70%
Portfolio Turnover 6% 13% 12% 14% 10%
(1) Computed using average shares outstanding.
(2) Returns are historical and are calculated by determining the percentage change in net asset value or market value with all distributions reinvested. Distributions are assumed to be reinvested at prices obtained under the Trust's dividend reinvestment plan.
(3) Excludes the effect of custody fee credits, if any, of less than 0.005%. Effective September 1, 2015, custody fee credits, which were earned on cash deposit balances, were discontinued by the custodian.
(4) Interest and fee expense relates to the liability for floating rate notes issued in conjunction with residual interest bond transactions.
Eaton Vance National Municipal Opportunities Trust 23 Prospectus dated July 22,2021

TRADING AND NAV INFORMATION

The Trust's Common Shares have traded both at a premium and a discount to NAV. The Trust cannot predict whether its shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of Common Shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company's common stock (calculated within 48 hours of pricing). The issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust's common shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Trust's Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV. See 'Additional Risk Considerations - Discount from or Premium to NAV'.

In addition, the Trust's Board of Trustees has authorized the Trust to repurchase up to 10% of its outstanding Common Shares as of the day of the prior calendar year-end at market prices when shares are trading at a discount to net asset value. The share repurchase program does not obligate the Trust to purchase a specific amount of shares. The results of the share repurchase program are disclosed in the Trust's annual and semi-annual reports to shareholders. See 'Description of Capital Structure - Repurchase of Common Shares and Other Discount Measures.'

The following table sets forth for each of the periods indicated the high and low closing market prices for Common Shares on the NYSE, and the corresponding NAV per share and the premium or discount to NAV per share at which the Trust's Common Shares were trading as of such date.

Market Price NAV per Share on Date of Market Price NAV Premium/(Discount) on Date of Market Price
Fiscal Quarter Ended High Low High Low High Low
6/30/2021 $23.45 $22.09 $22.11 $22.23 6.06% (0.63)%
3/31/2021 $22.74 $20.36 $21.72 $21.83 4.70% (6.73)%
12/31/2020 $21.50 $19.88 $21.52 $21.06 (0.09)% (5.60)%
9/30/2020 $20.78 $19.45 $21.57 $20.98 (3.66)% (7.29)%
6/30/2020 $19.65 $17.86 $20.93 $20.00 (6.12)% (10.70)%
3/31/2020 $23.12 $16.76 $22.30 $20.43 3.68% (17.96)%
12/31/2019 $24.09 $21.64 $21.49 $21.52 12.10% 0.56%
9/30/2019 $24.70 $21.92 $21.46 $21.62 15.10% 1.39%
6/30/2019 $23.84 $21.13 $21.44 $21.06 11.19% 0.33%

The last reported sale price, NAV per share and percentage premium/(discount) to NAV per share of the Common Shares as of July 20, 2021, were $23.14, $22.55 and 2.62%, respectively. As of July 20, 2021, the Trust had 15,396,359 Common Shares outstanding and net assets of the Trust were $347,118,606.

The following table provides information about our outstanding Common Shares as of July 20, 2021:

Title of Class Amount Authorized Amount Held by the Trust for its Account Amount Outstanding
Common Shares Unlimited 0 15,396,359

The Trust

The Trust is a diversified, closed-end management investment company registered under the 1940 Act. The Trust was organized as a Massachusetts business trust on January 26, 2009, pursuant to an Agreement and Declaration of Trust, as amended April 3, 2009, governed by the laws of The Commonwealth of Massachusetts. The Trust's principal office is located at Two International Place, Boston, MA 02110, and its telephone number is 1-800-262-1122.

Eaton Vance National Municipal Opportunities Trust 24 Prospectus dated July 22,2021

Use of Proceeds

Subject to the remainder of this section, and unless otherwise specified in a Prospectus Supplement, the Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus in accordance with its investment objectives and policies as described under 'Investment Objectives, Policies and Risks' within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the proceeds may be invested in short-term money market instruments, securities with remaining maturities of less than one year, cash and/or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust's distribution to Common Shareholders or result in a distribution consisting principally of a return of capital.

Portfolio Composition

As of March 31, 2021, the following sets forth certain information with respect to the composition of the Trust's investment portfolio:

Percentage of total investment portfolio invested in investment grade obligations 79.4%
Percentage of total investment portfolio invested in obligations rated below investment grade 20.6%
Rating(1) Number of issues Market Value Percentage
of Total Investment
Portfolio
AAA 5 $ 5,711,248 1.69%
AA 40 $ 107,257,072 31.68%
A 32 $ 56,224,471 16.61%
BBB 59 $ 99,610,593 29.42%
BB 19 $ 24,785,338 7.32%
B 7 $ 11,762,414 3.47%
C 1 $ 369,091 0.11%
Not rated 35 $ 32,858,381 9.70%
Total 198 $ 338,578,608 100%
(1) Ratings: Using the higher of S&P's, Moody's or Fitch's ratings on the Trust's investments. S&P and Fitch rating categories may be modified further by a plus (+) or minus
(-) in AA, A, BBB, BB, B, and CCC ratings. Moody's rating categories may be modified further by a 1, 2 or 3 in Aa, A, Baa, Ba, B, and Caa ratings. These ratings include the ratings of the municipal obligations held by tender option bond trusts in which the Trust holds a residual interest.

Investment Objectives, Policies and Risks

INVESTMENT OBJECTIVES

The Trust's primary investment objective is to provide current income exempt from federal income tax. The Trust will, as a secondary investment objective, seek to achieve capital appreciation. The Trust will seek to achieve its investment objectives by investing primarily in municipal obligations (as defined below) that, at the time of investment, are investment grade quality. The Trust also may invest a portion of its gross assets in municipal obligations rated below investment grade or unrated securities that the Adviser considers to be of comparable quality.

PRIMARY INVESTMENT POLICIES

General Composition of the Trust. During normal market conditions, the Trust will invest at least 80% of its gross assets in debt obligations issued by or on behalf of states, territories and possessions of the United States, including the District of Columbia, and their political subdivisions, agencies or instrumentalities, the interest on which is exempt from regular federal income tax ('municipal obligations'). For purposes of this 80% policy, municipal obligations will include investments in residual interest bonds whose interest is exempt from regular federal income tax. During normal market conditions, at least 70% of the Trust's investments in municipal obligations will be investment grade quality at time of

Eaton Vance National Municipal Opportunities Trust 25 Prospectus dated July 22,2021

investment. A municipal obligation is considered investment grade quality if it is either (i) rated within the four highest ratings categories by at least one nationally recognized statistical rating organization (a 'Rating Agency'), which are those rated Baa or higher by Moody's Investors Service, Inc. ('Moody's') or BBB or higher by Standard & Poor's Ratings Services ('S&P') or Fitch Ratings ('Fitch'), or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of investment grade quality. If a municipal obligation is rated differently by two or more Rating Agencies, the Trust will use the higher of such ratings (the 'Municipal Obligation Rating'). If a municipal obligation is insured, the Trust will use the higher of the Municipal Obligation Rating or the insurance issuer's rating. Securities rated in the fourth highest category (i.e., Baa by Moody's or BBB by S&P or Fitch) are considered investment grade quality, but may have speculative characteristics.

Up to 30% of the Trust's investments in municipal obligations may be in securities of issuers that are below investment grade quality at time of investment. A municipal obligation is considered below investment grade quality if it is either (i) rated below investment grade by a Rating Agency, or (ii) an unrated municipal obligation that the Trust's investment adviser considers to be of comparable quality. Municipal obligations of below investment grade quality (commonly referred to as 'junk' bonds) involve special risks as compared to municipal obligations of investment grade quality. These risks include greater sensitivity to a general economic downturn, greater market price volatility and less secondary market trading. The Trust may invest in below investment grade municipal obligations of any quality. This means that the Trust's investments in municipal obligations may include securities of issuers that are having financial difficulties, which may include being in default on obligations to pay principal or interest thereon when due or involved in bankruptcy or insolvency proceedings (such securities are commonly referred to as 'distressed securities'). The Trust generally will not invest more than 2% of its gross assets in any security rated below investment grade quality. For a description of municipal obligation ratings, see Appendix A to the SAI.

Up to 20% of the Trust's investments in municipal obligations may be subject to the alternative minimum tax.

The foregoing credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event that a Rating Agency downgrades its assessment of the credit characteristics of a particular issue or withdraws its assessment. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance's assessment of the credit quality of the issuer of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies.

The Trust has adopted certain fundamental investment restrictions set forth in the SAI which may not be changed without a vote of the holders of the Trust's common shares ('Common Shareholder'). Except for such restrictions and the 80% policy pertaining to investment in municipal obligations set forth above, the investment objectives and policies of the Trust may be changed by the Trust's Board of Trustees (the 'Board') without Common Shareholder action.

Under normal market conditions, the Trust will seek to maintain an average credit quality of investment grade. As indicated above, the Trust may invest in unrated obligations for which Eaton Vance will make a credit quality determination for purposes of the Trust's credit quality policy. To the extent that the Trust invests in such unrated obligations, the Trust's credit quality will be more dependent on Eaton Vance's credit analysis than if the Trust invested in only rated obligations. For a description of the risks of investing in below investment grade securities, see 'Investment Objectives, Policies and Risks - Risk Considerations - Below Investment Grade Securities Risk.'

If the Trust invests 25% or more of its gross assets in any one state (or U.S. territory) the Trust may be more susceptible to adverse economic, political or regulatory occurrences affecting a particular state (or territory).

The Trust is a 'diversified' investment company which means that with respect to 75% of its total assets (1) it may not invest more than 5% of its total assets in the securities of any one issuer and (2) it may not own more than 10% of the outstanding voting securities of any one issuer. Therefore, with respect to no more than 25% of its total assets, the Trust may invest more than 5% of the value of its total assets in the obligations of any single issuer. To the extent the Trust invests a relatively high percentage of its assets in obligations of a limited number of issuers, the Trust will be more susceptible to any single corporate, economic, political or regulatory occurrence.

The Trust may purchase and sell various kinds of financial futures contracts and related options, including futures contracts and related options based on various debt securities and securities indices. The Trust also may enter into interest rate, total return and other swaps and forward rate contracts to seek to hedge against changes in interest rates or for other risk management purposes.

The Trust may invest without limitation in derivative instruments (which are instruments that derive their value from another instrument, security or index) acquired for hedging purposes. See 'Investment Objectives, Policies and Risks - Additional Investment Practices - Derivative Instruments.'

During unusual market conditions, the Trust may invest up to 100% of its assets in cash or cash equivalents temporarily, which may be inconsistent with its investment objective(s) and other policies.

Eaton Vance National Municipal Opportunities Trust 26 Prospectus dated July 22,2021

Municipal Obligations. Municipal obligations include bonds (including general obligation and revenue bonds), notes and commercial paper issued by a municipality, a group of municipalities or participants in qualified issues of municipal debt for a wide variety of both public and private purposes.

Issuers of general obligation bonds include states, counties, cities, towns and regional districts. The proceeds of these obligations are used to fund a wide range of public projects, including the construction or improvement of schools, highways and roads, water and sewer systems and a variety of other public purposes. The basic security of general obligation bonds is the issuer's pledge of its faith, credit, and taxing power for the payment of principal and interest. The taxes that can be levied for the payment of debt service may be limited or unlimited as to rate and amount. General obligation bonds issued by municipalities can be adversely affected by economic downturns and the resulting decline in tax revenues, pension funding risk, other post-employment benefit risk, budget imbalances, taxing ability risk, lack of political willpower and federal funding risk, among others. Revenue bonds are payable only from the revenues derived from a particular facility or class of facilities or, in some cases, from the proceeds of a special excise tax or other specific revenue source such as payments from the user of the facility being financed. Revenue bonds can be adversely affected by the negative economic viability of the facility or revenue source. Industrial development bonds are normally secured by the revenues from the project and not by state or local government tax payments. They are subject to a wide variety of risks, many of which relate to the nature of the specific project. Generally industrial development bonds are sensitive to the risk of a slowdown in the economy. Municipal obligations also include municipal lease obligations and certificates of participations in municipal leases.

Certain municipal obligations may be purchased on a 'when-issued' basis, which means that payment and delivery occur on a future settlement date. The price and yield of such securities are generally fixed on the date of commitment to purchase.

The Trust may invest in zero coupon bonds, which do not make cash interest payments during a portion or all of the life of the bond. Instead, such bonds are sold at a deep discount to face value, and the interest consists of the gradual appreciation in price as the bond approaches maturity. Zero coupon bonds can be an attractive financing method for issuers with near-term cash-flow problems or seeking to preserve liquidity. Principal only investments entitle the Trust to receive the stated value of such investment when held to maturity. The values of zero coupon bonds and principal only investments are subject to greater fluctuation in response to changes in market interest rates than municipal obligations that pay interest currently. The Trust is required to distribute to shareholders income imputed to any zero coupon bonds or principal only investments even though such income may not be received by the Trust as distributable cash. Such distributions could reduce the Trust's reserve position and require it to sell securities and incur a gain or loss at a time it may not otherwise want to in order to provide the cash necessary for these distributions.

The interest on tax-exempt municipal obligations is (in the opinion of the issuer's counsel) exempt from regular federal income and state or local taxes, as applicable. Income from certain types of municipal obligations generally may be subject to the federal alternative minimum tax (the 'AMT') for individuals. Investors subject to AMT should consult their tax advisors.

Many municipal obligations provide the issuer the option to 'call,' or redeem, its securities. As such, the effective maturity of a municipal obligation may be reduced as the result of such call provisions and, if an investment is called in a declining interest rate environment, the proceeds from the called bond may have to be reinvested at a lower interest rate.

Up to 5% of the Trust's investments in municipal obligations may be collateralized by the proceeds from class action or other litigation against the tobacco industry. Such municipal obligations are backed solely by expected revenues to be derived from lawsuits involving tobacco-related deaths and illnesses which were settled between certain states and American tobacco companies. Tobacco settlement bonds are secured by an issuing state's proportionate share in the Master Settlement Agreement ('MSA'). The MSA is an agreement, reached out of court in November 1998 between 46 states and nearly all of the U.S. tobacco manufacturers. Under the terms of the MSA, the actual amount of future settlement payments by tobacco manufacturers is dependent on many factors, including, but not limited to, annual domestic cigarette shipments, reduced cigarette consumption, increased taxes on cigarettes, inflation, financial capability of tobacco companies, continuing litigation and the possibility of tobacco manufacturer bankruptcy. Payments made by tobacco manufacturers could be negatively impacted if the decrease in tobacco consumption is significantly greater than the forecasted decline. See 'State Specific Investments' in the SAI for additional information about tobacco settlement bonds and the MSA.

Municipal Lease Obligations ('MLOs') and Certificates of Participation. MLOs are bonds that are secured by lease payments made by the party, typically a state or municipality, leasing the facilities (e.g., schools or office buildings) that were financed by the bond. Interest income from MLOs is generally exempt from local and state taxes in the state of issuance. MLOs, like other municipal debt obligations, are subject to the risk of non-payment. Although MLOs do not constitute general obligations of the issuer for which the issuer's unlimited taxing power is pledged, the leasing state of municipality may be obligated to appropriate funds from its general tax revenues to make lease payments as long as it

Eaton Vance National Municipal Opportunities Trust 27 Prospectus dated July 22,2021

utilizes the leased property. Other lease payments may be subject to annual appropriation or may be made only from revenues associated with the facility financed. For example, certain lease obligations contain 'non-appropriation' clauses, which provide that the issuer has no obligation to make lease or installment purchase payments in future years unless money is appropriated for such purpose on a yearly basis. Although 'non-appropriation' lease obligations may be secured by the leased property, disposition of the property in the event of foreclosure might prove difficult. A certificate of participation (also referred to as a 'participation') in a municipal lease is an instrument evidencing a pro rata share in a specific pledged revenue stream, usually lease payments by the issuer that are typically subject to annual appropriation. The certificate generally entitles the holder to receive a share, or participation, in the payments from a particular project.

MLOs and participations therein represent a type of financing that may not have the depth of marketability associated with more conventional securities and, as such, they may be less liquid than conventional securities.

The ability of issuers of MLOs to make timely lease payments may be adversely impacted in general economic downturns and as relative governmental cost burdens are allocated and reallocated among federal, state and local governmental units. Such non-payment would result in a reduction of income from and value of the obligation. Issuers of MLOs might seek protection under the bankruptcy laws. In the event of bankruptcy of such an issuer, holders of MLOs could experience delays and limitations with respect to the collection of principal and interest on such MLOs and may not, in all circumstances, be able to collect all principal and interest to which it is entitled. To enforce its rights in the event of a default in lease payments, the Trust might take possession of and manage the assets securing the issuer's obligations on such securities or otherwise incur costs to protect its right, which may increase the Trust's operating expenses and adversely affect the net asset value of the Trust. When the lease contains a non-appropriation clause, however, the failure to pay would not be a default and the Trust would not have the right to take possession of the assets. Any income derived from the Trust's ownership or operation of such assets may not be tax-exempt.

Municipal Notes. Municipal securities in the form of notes, generally are used by municipal issuers to provide for short-term capital needs, in anticipation of an issuer's receipt of other revenues or financing, and typically have maturities of up to three years. Municipal notes include bond anticipation, tax anticipation and revenue anticipation notes. Bond, tax and revenue anticipation notes are short-term obligations that are intended to be retired with the proceeds of an anticipated bond issue, tax revenue or facility revenue, respectively. Generally, tax anticipation notes are issued in anticipation of various tax revenues, such as income, sales, property, use and business taxes, and are payable from these specific future taxes. Revenue anticipation notes are issued in expectation of receipt of other kinds of revenue, such as federal revenues available under federal revenue sharing programs. Bond anticipation notes are issued to provide interim financing until long-term bond financing can be arranged. In most cases, the long-term bonds then provide the funds needed for repayment of the bond anticipation notes. Tax and revenue anticipation notes combine individual characteristics of tax anticipation notes and revenue anticipation notes. The anticipated revenues from taxes, grants or bond financing generally secure the obligations of an issuer of municipal notes. An investment in such instruments, however, presents a risk that the anticipated revenues will not be received or that such revenues will be insufficient to satisfy the issuer's payment obligations under the notes or that refinancing will be otherwise unavailable.

Residual Interest Bonds. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. In general, income on residual interest bonds will decrease when short-term interest rates increase and increase when short-term interest rates decrease. Residual interest bonds have varying degrees of liquidity, and the market for these securities is relatively volatile. Residual interest bonds create investment leverage in the Trust because they provide more than one dollar of exposure to municipal bonds for each dollar the Trust invests in them.

The Trust may invest in residual interest bonds, also referred to as inverse floating rate securities, whereby the Trust may sell a variable or fixed rate bond for cash to a SPV, (which is generally organized as a trust), while at the same time, buying a residual interest in the assets and cash flows of the SPV. The bond is deposited into the SPV with the same CUSIP number as the bond sold to the SPV by the Trust, and which may have been, but is not required to be, the bond purchased from the Trust (the 'Bond'). The SPV also issues Floating Rate Notes which are sold to third-parties. The residual interest bond held by the Trust gives the Trust the right (1) to cause the holders of the Floating Rate Notes to generally tender their notes at par, and (2) to have the Bond held by the SPV transferred to the Trust, thereby terminating the SPV. Should the Trust exercise such right, it would generally pay the SPV the par amount due on the Floating Rate Notes and exchange the residual interest bond for the underlying Bond. Pursuant to generally accepted accounting principles, the Trust accounts for the transaction described above as a secured borrowing by including the Bond in its portfolio of investments and the Floating Rate Notes as a liability. The Floating Rate Notes have interest rates that generally reset weekly and their holders have the option to tender their notes to the SPV for redemption at par at each reset date. The SPV may be terminated by the Trust, as noted above, or by the occurrence of certain termination events as defined in the trust agreement, such as a downgrade in the credit quality of the underlying Bond, bankruptcy of or payment failure by the issuer of the underlying Bond, the inability to remarket Floating Rate Notes that have been tendered due to insufficient buyers in the market, or the failure by the SPV to obtain renewal of the liquidity agreement under which liquidity support is provided for the Floating Rate Notes up to one year.

Eaton Vance National Municipal Opportunities Trust 28 Prospectus dated July 22,2021

In certain circumstances, the Trust may enter into shortfall and forbearance agreements relating to a residual interest bond held by the Trust. Such agreements commit the Trust to reimburse the difference between the liquidation value of the underlying security (which is the basis of the residual interest bond) and the principal amount due to the holders of the floating rate security issued in conjunction with the residual interest bond upon the termination of the trust issuing the residual interest bond. Absent a shortfall and forbearance agreement, the Trust would not be required to make such a reimbursement. If the Trust chooses not to enter into such an agreement, the residual interest bond could be terminated and the Trust could incur a loss. The Trust had no shortfalls as of March 31, 2021.

The Trust may also purchase residual interest bonds in a secondary market transaction without first owning the underlying bond. Such transactions are not required to be treated as secured borrowings.

The Trust's investment policies and restrictions expressly permit investments in residual interest bonds. Such bonds typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. The value and income of residual interest bonds are generally more volatile than that of a fixed rate bond. The Trust's investment policies do not allow the Trust to borrow money except as permitted by the 1940 Act. The Adviser believes that the Trust's restrictions on borrowing money and issuing senior securities (other than as specifically permitted) do not apply to Floating Rate Notes issued by the SPV and included as a liability in the Trust's statement of assets and liabilities. As secured indebtedness issued by an SPV, Floating Rate Notes are distinct from the borrowings and senior securities to which the Trust's restrictions apply. Residual interest bonds held by the Trust are securities exempt from registration under Rule 144A of the Securities Act of 1933, as amended (the 'Securities Act').

The Trust will segregate or earmark liquid assets at its custodian equal to the value of economic leverage created by residual interest bonds, whether initiated by the Trust or purchased on the secondary market.

As of March 31, 2021, 3.03% of the Trust's net assets were invested in residual interest bonds.

As of March 31, 2021, the actual leverage attributable to the floating-rate notes was 6.52% of the Trust's net assets.

Short-Term Floating Rate Securities. The Trust may also invest in Floating-Rate Notes, as described above, issued by SPVs. The short-term floating rate security will be linked to a reference interest rate (such as LIBOR or the SIFMA Municipal Bond Swap Index) and the SPV's income will be used to pay the coupon on the Floating-Rate Notes. Generally, the interest rate earned on Floating-Rate Notes will be based upon the market rates for municipal obligations with maturities or remarketing provisions that are comparable in duration to the periodic interval of the tender option, which may vary from weekly, to monthly, to extended periods of one year or multiple years. Since the option feature has a shorter term than the final maturity or first call date of the underlying bond deposited in the trust, the Trust as the holder of the Floating-Rate Notes relies upon the terms of the agreement with the financial institution furnishing the option as well as the credit strength of that institution. As further assurance of liquidity, the terms of the SPV provide for a liquidation of the Bond and the application of the proceeds to pay off the Floating-Rate Notes. The SPVs that are organized to issue both Floating-Rate Notes and residual interest bonds generally include liquidation triggers to protect the investor in the Floating-Rate Notes. Generally, the SPVs do not have recourse to the investors in the residual interest bonds. However, the Trust may invest in residual interest securities issued by tender option bond trusts that may have recourse to the Trust's other assets. In such instances, the Trust may be at risk of loss that exceeds its investment in the residual interest securities. The Trust will segregate or earmark liquid assets with its custodian on a mark-to-market basis to cover such potential obligations.

Leverage. The Trust currently uses leverage to seek to enhance returns by investing in residual interest bonds. The Trust will not utilize leverage in excess of 15% of its gross assets. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. Although the Trust has no current intention to do so, the Trust is authorized also to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act.

The Adviser anticipates that the use of leverage (from residual interest bonds) may result in higher income to holders of Common Shares ('Common Shareholders') over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful. The investment advisory fee paid to Eaton Vance will be calculated on the basis of the Trust's average daily gross assets. 'Gross assets' of the Trust means total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing

Eaton Vance National Municipal Opportunities Trust 29 Prospectus dated July 22,2021

through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. This means that the Trust's advisory fees will be higher when leverage is utilized which may create an incentive for the Adviser to employ leverage. In this regard, holders of debt or preferred shares do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds from the use of leverage, which means that Common Shareholders effectively bear the entire advisory fee. See 'Investment Objectives, Policies and Risks - Use of Leverage and Related Risks' at page 32, 'Investment Objectives, Policies and Risks - Additional Risk Considerations' at page 35 and 'Description of Capital Structure' at page 51.

In addition to investing in residual interest bonds, the Trust may invest without limitation in other derivative instruments (which are instruments that derive their value from another instrument, security or index) acquired for hedging purposes.

ADDITIONAL INVESTMENT PRACTICES

Derivative Instruments. The Trust may invest without limitation in derivative instruments (which are instruments that derive their value from a reference instrument) acquired for hedging purposes. Depending on the type of derivative instrument and the Trust's investment strategy, a reference instrument could be a security, instrument, index, currency, commodity, economic indicator or event ('reference instruments'). In the course of pursuing these investment strategies, the Trust may purchase and sell derivative contracts based on securities indices and other instruments, purchase and sell futures contracts and options thereon, and enter into various transactions such as swaps, caps, floors or collars. In addition, derivatives may also include new techniques, instruments or strategies that are not currently available. Derivative instruments may be used by the Trust to enhance returns or as a substitute for the purchase or sale of securities. The loss on derivative instruments (other than purchased options) may substantially exceed an investment in these instruments. Additional information about certain derivative instruments is set forth below.

Swaps. Swap contracts may be purchased or sold to hedge against fluctuations in securities prices, interest rates or market conditions, to mitigate non-payment or default risk or to gain exposure to particular securities, baskets of securities, indices or currencies. In a standard 'swap' transaction, two parties agree to exchange the returns (or differentials in rates of return) on different currencies, securities, baskets of currencies or securities, indices or other instruments, which returns are calculated with respect to a 'notional amount,' i.e., the designated referenced amount of exposure to the underlying instruments. The Trust will enter into swaps only on a net basis, i.e., the two payment streams are netted out, with the Trust receiving or paying, as the case may be, only the net amount of the two payments. If the other party to a swap defaults, the Trust's risk of loss consists of the net amount of payments that the Trust is contractually entitled to receive that is in excess of collateral posted by the Trust's counterparty in respect of such liability. The net amount of the excess, if any, of the Trust's obligations over its entitlements will be maintained in a segregated account by the Trust's custodian. The Trust will not enter into any swap unless the claims-paying ability of the other party thereto is considered to be investment grade by the Adviser. If there is a default by the other party to such a transaction, the Trust will have contractual remedies pursuant to the agreements related to the transaction. Swaps are traded in the over-the-counter market. The use of swaps is a highly specialized activity, which involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. If the Adviser is incorrect in its forecasts of market values, interest rates and other applicable factors, the total return performance of the Trust would be unfavorably affected.

Total Return Swaps. A total return swap is a contract in which one party agrees to make periodic payments to another party based on the change in market value of a reference instrument during the specified period, in return for periodic payments from the other party that are based on a fixed or variable interest rate or the total return of the reference instrument or another reference instrument. Total return swap agreements may be used to obtain exposure to a security or market without owning or taking physical custody of such security or investing directly in such market.

Interest Rate Swaps and Forward Rate Contracts. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interest, e.g., an exchange of fixed rate payments for floating rate payments. The Trust will only enter into interest rate swaps on a net basis, i.e., the two payment streams are netted out with the Trust receiving or paying, as the case may be, only the net amount of the two payments. The Trust may also enter forward rate contracts. Under these contracts, the buyer locks in an interest rate at a future settlement date. If the interest rate on the settlement date exceeds the lock rate, the buyer pays the seller the difference between the two rates. If the lock rate exceeds the interest rate on the settlement date, the seller pays the buyer the difference between the two rates. Any such gain received by the Trust would be taxable.

Eaton Vance National Municipal Opportunities Trust 30 Prospectus dated July 22,2021

If the other party to an interest rate swap or forward rate contract defaults, the Trust's risk of loss consists of the net amount of payments that the Trust is contractually entitled to receive that is in excess of collateral posted by the Trust's counterparty in respect of such liability. The net amount of the excess, if any, of the Trust's obligations over its entitlements will be maintained in a segregated account by the Trust's custodian. The Trust will not enter into any interest rate swap or forward rate contract unless the claims-paying ability of the other party thereto is considered to be investment grade by the Adviser. If there is a default by the other party to such a transaction, the Trust will have contractual remedies pursuant to the agreements related to the transaction. These instruments are traded in the over-the-counter market.

Futures Transactions. The Trust may purchase and sell various kinds of financial futures contracts and options thereon to seek to hedge against changes in interest rates or for other risk management or investment purposes. Futures contracts may be based on various debt securities and securities indices. Such transactions involve a risk of loss or depreciation due to unanticipated adverse changes in securities prices, which may exceed the Trust's initial investment in these contracts. The Trust only will purchase or sell futures contracts or related options in compliance with the rules of the Commodity Futures Trading Commission. These transactions involve transaction costs. There can be no assurance that Eaton Vance's use of futures will be advantageous to the Trust. Distributions by the Trust of any gains realized on the Trust's transactions in futures and options on futures will be taxable.

Zero-Coupon Bonds. Some of the obligations in which the Trust invests may include so-called 'zero-coupon' bonds, whose values generally are subject to greater fluctuation in response to changes in market interest rates than bonds that pay interest currently. Zero-coupon bonds are issued at a discount from face value and pay interest only at maturity rather than at intervals during the life of the security. The Trust is required to take into account imputed income from zero-coupon bonds on a current basis, even though it does not receive that income currently in cash. Because the Trust is required to distribute substantially all of its income for each taxable year, investments in zero-coupon bonds may require the Trust to sell investments to obtain cash needed to make income distributions.

When-Issued Securities. The Trust may purchase securities on a 'when-issued' basis, which means that payment and delivery occur on a future settlement date. The price and yield of such securities are generally fixed on the date of commitment to purchase. However, the market value of the securities may fluctuate prior to delivery, and upon delivery the securities may be worth more or less than what the Trust agreed to pay for them. The Trust may be required to maintain a segregated account of liquid assets equal to outstanding purchase commitments. The Trust may also purchase instruments that give the Trust the option to purchase a municipal obligation when and if issued.

Investment Company Securities. The Trust may purchase common shares of closed-end investment companies that have investment objectives and policies similar to those of the Trust. In addition to providing tax-exempt income, such securities may provide capital appreciation. Such investments, which may also be leveraged and subject to similar risks as the Trust, will not exceed 10% of the Trust's gross assets. These companies bear fees and expenses that the Trust will incur indirectly. The Trust will not invest in other investment companies that are affiliated with Eaton Vance.

Portfolio Turnover. The Trust cannot accurately predict its portfolio turnover rate, but its historical annual turnover rate over the last five years has been between 11% and 44% (excluding turnover of securities and obligations having a maturity of one year or less). For the fiscal years ended March 31, 2021 and March 31, 2020, the Trust's portfolio turnover rates were 13% and 44%, respectively. The Trust may engage in active short-term trading to benefit from yield disparities among different issues, to seek short-term profits or for other reasons. Such trading will increase the Trust's rate of turnover and may increase the incidence of net short-term capital gains which, upon distribution by the Trust, are taxable to Common Shareholders as ordinary income.

Restricted Securities. Securities held by the Trust may be legally restricted as to resale (such as those issued in private placements), including commercial paper issued pursuant to Section 4(a)(2) of the 1933 Act and securities eligible for resale pursuant to Rule 144A thereunder, and securities of U.S. and non-U.S. issuers initially offered and sold outside the United States pursuant to Regulation S thereunder. Restricted securities may not be listed on an exchange and may have no active trading market. The Trust may incur additional expense when disposing of restricted securities, including all or a portion of the cost to register the securities. The Trust also may acquire securities through private placements under which it may agree to contractual restrictions on the resale of such securities that are in addition to applicable legal restrictions. In addition, if the Adviser receives material non-public information about the issuer, the Trust may as a result be unable to sell the securities. Restricted securities may be difficult to value properly and may involve greater risks than securities that are not subject to restrictions on resale. It may be difficult to sell restricted securities at a price representing fair value until such time as the securities may be sold publicly. Under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Trust could find it more difficult to sell such securities when the Adviser believes it advisable to do so or may be able to sell such securities only at prices lower than if such securities were more widely held. Holdings of restricted securities may increase the level of Trust illiquidity if eligible buyers become uninterested in purchasing them. Restricted securities may involve a high degree of business and financial risk, which may result in substantial losses.

Eaton Vance National Municipal Opportunities Trust 31 Prospectus dated July 22,2021

Illiquid Investments. The Trust may invest in investments for which there is no readily available trading market or that are otherwise illiquid. It may be difficult to sell illiquid investments at a price representing their fair value until such time as such investments may be sold publicly. Where registration is required, a considerable period may elapse between a decision by the Trust to sell the investments and the time when it would be permitted to sell. Thus, the Trust may not be able to obtain as favorable a price as that prevailing at the time of the decision to sell. The Trust may also acquire investments through private placements under which it may agree to contractual restrictions on the resale of such investments. Such restrictions might prevent their sale at a time when such sale would otherwise be desirable.

At times, a portion of the Trust's assets may be invested in investments as to which the Trust, by itself or together with other accounts managed by the Adviser and its affiliates, holds a major portion or all of such investments. Under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Trust could find it more difficult to sell such investments when the Adviser believes it advisable to do so or may be able to sell such investments only at prices lower than if such investments were more widely held. It may also be more difficult to determine the fair value of such investments for purposes of computing the Trust's net asset value.

Research Process. The Trust's portfolio management utilizes the information provided by, and the expertise of, the research staff of the investment adviser and/or certain of its affiliates in making investment decisions. As part of the research process, portfolio management may consider financially material environmental, social and governance ('ESG') factors. Such factors, alongside other relevant factors, may be taken into account in the Trust's securities selection process.

Temporary Investments. During unusual market conditions, the Trust may invest up to 100% of its assets in cash or cash equivalents temporarily, which may be inconsistent with its investment objectives, principal strategies and other policies. Cash equivalents are highly liquid, short-term securities such as commercial paper, time deposits, certificates of deposit, short-term notes and short-term United States government obligations. In moving to a substantial temporary investments position and in transitioning from such a position back into conformity with the Trust's normal investment policies, the Trust may incur transaction costs that would not be incurred if the Trust had remained fully invested in accordance with such normal policies. The transition to and from a substantial temporary investments position may also result in the Trust having to sell common stocks and/or close out options positions and then later purchase common stocks and open new options positions in circumstances that might not otherwise be optimal. The Trust's investment in such temporary investments under unusual market circumstances may not be in furtherance of the Trust's investment objectives.

USE OF LEVERAGE AND RELATED RISKS

As described herein, the Trust may invest in residual interest bonds, which have the economic effect of leverage. As of March 31, 2021, the Trust had leverage in the form of residual interest bonds. The Adviser anticipates that the use of leverage (from investment in residual interest bonds) may result in higher income to Common Shareholders over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will successful.

The costs of the financial leverage program (from investment in residual interest bonds and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the NAV of Common Shares. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust's gross assets, which means the total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. In this regard, holders of debt or preferred shares do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee.

Leverage creates risks for holders of the Common Shares, including the likelihood of greater volatility of NAV and market price of the Common Shares. There is a risk that the costs of leverage may adversely affect the return to the holders of the Common Shares. If the income from the investments purchased with the proceeds of leverage is not sufficient to cover the cost of leverage, the return on the Trust will be less than if leverage had not been used, and, therefore, the amount available for distribution to Common Shareholders will be reduced. The Adviser in its best judgment nevertheless may determine to maintain the Trust's leveraged position if it deems such action to be appropriate in the circumstances.

Eaton Vance National Municipal Opportunities Trust 32 Prospectus dated July 22,2021

Changes in the value of the Trust's investment portfolio (including investments bought with the proceeds of leverage) will be borne entirely by the Common Shareholders. If there is a net decrease (or increase) in the value of the Trust's investment portfolio, the leverage will decrease (or increase) the NAV per Common Share to a greater extent than if the Trust were not leveraged. As discussed under 'Description of Capital Structure,' the Trust's issuance of any preferred shares may alter the voting power of Common Shareholders.

Capital raised through leverage will be subject to distribution and/or interest payments, which may exceed the income and appreciation on the assets purchased. The issuance of a class of preferred shares involves offering expenses and other costs and may limit the Trust's freedom to pay distributions on Common Shares or to engage in other activities. The issuance of a class of preferred shares having priority over the Common Shares creates an opportunity for greater return per Common Share, but at the same time such leveraging is a speculative technique that will increase the Trust's exposure to capital risk. Unless the income and appreciation, if any, on assets acquired with offering proceeds exceed the cost of issuing additional classes of securities (and other Trust expenses), the use of leverage will diminish the investment performance of the Common Shares compared with what it would have been without leverage.

The Trust may be subject to certain restrictions on investments imposed by guidelines of one or more Rating Agencies that may issue ratings for any preferred shares issued by the Trust. Any bank lender in connection with a credit facility or commercial paper program may also impose specific restrictions as a condition to borrowing. Such restrictions imposed by a Rating Agency or lender may include asset coverage or portfolio composition requirements that are more stringent than those imposed on the Trust by the 1940 Act. It is not anticipated that these covenants or guidelines will significantly impede Eaton Vance from managing the Trust's portfolio in accordance with its investment objectives and policies.

Under the 1940 Act, the Trust is not permitted to issue preferred shares unless immediately after such issuance the total asset value of the Trust's portfolio is at least 200% of the liquidation value of the outstanding preferred shares plus the amount of any senior security representing indebtedness (i.e., such liquidation value and amount of indebtedness may not exceed 50% of the Trust's total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust's portfolio (determined after deducting the amount of such distribution) is at least 200% of such liquidation value plus amount of indebtedness. If preferred shares are issued, the Trust intends, to the extent possible, to purchase or redeem preferred shares, from time to time, to maintain coverage of any preferred shares of at least 200%. As of March 31, 2021, the leverage attributable to floating-rate notes represented 6.52% of the Trust's gross assets. Holders of any preferred shares, voting as a class, would be entitled to elect two of the Trust's Trustees. The holders of both the Common Shares and any preferred shares (voting together as a single class with each share entitling its holder to one vote) would be entitled to elect the remaining Trustees of the Trust. In the event the Trust fails to pay distributions on its preferred shares for two years, preferred shareholders would be entitled to elect a majority of the Trustees until the preferred distributions in arrears are paid. The Trust has no current intention to issue preferred shares.

Under the 1940 Act, the Trust is not permitted to incur indebtedness, including through the issuance of debt securities, unless immediately thereafter the total asset value of the Trust's portfolio is at least 300% of the liquidation value of the outstanding indebtedness (i.e., such liquidation value may not exceed 33 1/3% of the Trust's total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust's portfolio (determined after deducting the amount of such distribution) is at least 300% of such liquidation value. If the Trust borrows money or enters into a commercial paper program, the Trust intends, to the extent possible, to retire outstanding debt, from time to time, to maintain coverage of any outstanding indebtedness of at least 300%. As of March 31, 2021, there were no outstanding borrowings.

To qualify for federal income taxation as a 'regulated investment company,' the Trust must distribute in each taxable year at least 90% of its net investment income (including net interest income and net short-term gain). The Trust also will be required to distribute annually substantially all of its income and capital gain, if any, to avoid imposition of a nondeductible 4% federal excise tax. If the Trust is precluded from making distributions on the Common Shares because of any applicable asset coverage requirements, the terms of the preferred shares may provide that any amounts so precluded from being distributed, but required to be distributed for the Trust to meet the distribution requirements for qualification as a regulated investment company, will be paid to the holders of the preferred shares as a special distribution. This distribution can be expected to decrease the amount that holders of preferred shares would be entitled to receive upon redemption or liquidation of the shares.

Successful use of a leveraging strategy may depend on the Adviser's ability to predict correctly interest rates and market movements, and there is no assurance that a leveraging strategy will be successful during any period in which it is employed.

Eaton Vance National Municipal Opportunities Trust 33 Prospectus dated July 22,2021

Residual Interest Bonds. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. In general, income on residual interest bonds will decrease when short-term interest rates increase and increase when short-term interest rates decrease. Residual interest bonds have varying degrees of liquidity, and the market for these securities is relatively volatile. Residual interest bonds create investment leverage in the Trust because they provide more than one dollar of exposure to municipal bonds for each dollar the Trust invests in them.

The Trust may invest in residual interest bonds, also referred to as inverse floating rate securities, whereby the Trust may sell a variable or fixed rate bond for cash to a SPV, (which is generally organized as a trust), while at the same time, buying a residual interest in the assets and cash flows of the SPV. The bond is deposited into the SPV with the same CUSIP number as the bond sold to the SPV by the Trust, and which may have been, but is not required to be, the bond purchased from the Trust (the 'Bond'). The SPV also issues Floating Rate Notes which are sold to third-parties. The residual interest bond held by the Trust gives the Trust the right (1) to cause the holders of the Floating Rate Notes to generally tender their notes at par, and (2) to have the Bond held by the SPV transferred to the Trust, thereby terminating the SPV. Should the Trust exercise such right, it would generally pay the SPV the par amount due on the Floating Rate Notes and exchange the residual interest bond for the underlying Bond. Pursuant to generally accepted accounting principles the Trust accounts for the transaction described above as a secured borrowing by including the Bond in its portfolio of investments and the Floating Rate Notes as a liability. The Floating Rate Notes have interest rates that generally reset weekly and their holders have the option to tender their notes to the SPV for redemption at par at each reset date. The SPV may be terminated by the Trust, as noted above, or by the occurrence of certain termination events as defined in the trust agreement, such as a downgrade in the credit quality of the underlying Bond, bankruptcy of or payment failure by the issuer of the underlying Bond, the inability to remarket Floating Rate Notes that have been tendered due to insufficient buyers in the market, or the failure by the SPV to obtain renewal of the liquidity agreement under which liquidity support is provided for the Floating Rate Notes up to one year.

In certain circumstances, the Trust may enter into shortfall and forbearance agreements with respect to a residual interest bond. The Trust generally may enter into such agreements (i) when the liquidity provider to the SPV requires such an agreement because the level of leverage in the SPV exceeds the level that the liquidity provider is willing support absent such an agreement; and/or (ii) to seek to prevent the liquidity provider from collapsing the SPV in the event that the municipal obligation held in the SPV has declined in value. Such agreements commit the Trust to reimburse, upon the termination of the SPV, the difference between the liquidation value of the underlying security (which is the basis of the inverse floater) and the principal amount due to the holders of the floating rate security issued in conjunction with the inverse floater. Such agreements may expose the Trust's other assets to losses. Absent a shortfall and forbearance agreement, the Trust would not be required to make such a reimbursement. If the Trust chooses not to enter into such an agreement, the inverse floater could be terminated and the Trust could incur a loss. Consistent with SEC staff guidance, the Trust will segregate or earmark liquid assets with its custodian on a mark-to-market basis to cover any such payment obligations to liquidity providers. The Trust had no shortfalls as of March 31, 2021.

The Trust may also purchase residual interest bonds in a secondary market transaction without first owning the underlying bond. Such transactions are not required to be treated as secured borrowings.

The Trust's investment policies and restrictions expressly permit investments in residual interest bonds. Such bonds typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. The value and income of residual interest bonds are generally more volatile than that of a fixed rate bond. The Trust's investment policies do not allow the Trust to borrow money except as permitted by the 1940 Act. The Adviser believes that the Trust's restrictions on borrowing money and issuing senior securities (other than as specifically permitted) do not apply to Floating Rate Notes issued by the SPV and included as a liability in the Trust's statement of assets and liabilities. As secured indebtedness issued by an SPV, Floating Rate Notes are distinct from the borrowings and senior securities to which the Trust's restrictions apply. Residual interest bonds held by the Trust are securities exempt from registration under Rule 144A of the Securities Act of 1933, as amended (the 'Securities Act').

The Trust will segregate or earmark liquid assets at its custodian equal to the value of economic leverage created by residual interest bonds, whether initiated by the Trust or purchased on the secondary market.

Eaton Vance National Municipal Opportunities Trust 34 Prospectus dated July 22,2021

The following table is designed to illustrate the effect on the return to a holder of the Common Shares of leverage in the amount of approximately 6.10% of the Trust's gross assets, assuming hypothetical annual returns of the Trust's portfolio of minus 10% to plus 10%. As the table shows, leverage generally increases the return to Common Shareholders when portfolio return is positive and greater than the cost of leverage and decreases the return when the portfolio return is negative or less than the cost of leverage. The figures appearing in the table are hypothetical and actual returns may be greater or less than those appearing in the table.

Assumed Portfolio Return (Net of expenses) (10)% (5)% 0% 5% 10%
Corresponding Common Share Total Return (10.70)% (5.38)% (0.05)% 5.27% 10.60%

Assuming the utilization of leverage in the amount of 6.10% of the Trust's gross assets, the cost of leverage is 0.80%. The additional income that the Trust must earn (net of expenses) in order to cover such costs is approximately 0.05% of gross assets. The Trust's actual costs of leverage will be based on market rates at the time the Trust undertakes a leveraging strategy, and such actual costs of leverage may be higher or lower than that assumed in the previous example.

ADDITIONAL RISK CONSIDERATIONS

Risk is inherent in all investing. Investing in any investment company security involves risk, including the risk that you may receive little or no return on your investment or even that you may lose part or all of your investment.

Discount From or Premium to NAV. The Offering will be conducted only when Common Shares of the Trust are trading at a price equal to or above the Trust's NAV per Common Share plus the per Common Share amount of commissions. As with any security, the market value of the Common Shares may increase or decrease from the amount initially paid for the Common Shares. The Trust's Common Shares have traded both at a premium and at a discount relative to net asset value. The shares of closed-end management investment companies frequently trade at a discount from their NAV. This is a risk separate and distinct from the risk that the Trust's NAV may decrease.

Secondary Market for the Common Shares. The issuance of Common Shares through the Offering may have an adverse effect on the secondary market for the Common Shares. The increase in the amount of the Trust's outstanding Common Shares resulting from the Offering may put downward pressure on the market price for the Common Shares of the Trust. Common Shares will not be issued pursuant to the Offering at any time when Common Shares are trading at a price lower than a price equal to the Trust's NAV per Common Share plus the per Common Share amount of commissions.

The Trust also issues Common Shares of the Trust through its dividend reinvestment plan. See 'Dividend Reinvestment Plan.' Common Shares may be issued under the plan at a discount to the market price for such Common Shares, which may put downward pressure on the market price for Common Shares of the Trust.

When the Common Shares are trading at a premium, the Trust may also issue Common Shares of the Trust that are sold through transactions effected on the NYSE. The increase in the amount of the Trust's outstanding Common Shares resulting from that offering may also put downward pressure on the market price for the Common Shares of the Trust.

The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any future Common Share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if the Adviser is unable to invest the proceeds of such offering as intended, the Trust's per share distribution may decrease (or may consist of return of capital) and the Trust may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Investment and Market Risk. An investment in Common Shares is subject to investment risk, including the possible loss of the entire principal amount invested. An investment in Common Shares represents an indirect investment in the securities owned by the Trust, which will generally trade in the over-the-counter ('OTC') markets. The Common Shares at any point in time may be worth less than the original investment, even after taking into account any reinvestment of distributions.

Interest Rate and Income Risk. When interest rates decline, the value of municipal obligations held by the Trust can be expected to rise. Conversely, when interest rates rise, the value of municipal obligations held by the Trust can be expected to decline. Interest rate risk is the risk that the municipal obligations in the Trust's portfolio will decline in value because of increases in market interest rates. Generally, obligations with longer durations or maturities are more sensitive to changes in interest rates than obligations with shorter durations or maturities, causing them to be more volatile. Conversely, obligations with shorter durations or maturities will be less volatile but may provide lower returns than obligations with longer durations or maturities. A decline in the prices of the municipal obligations owned by the Trust would cause a decline in the NAV of the Trust, which could adversely affect the trading price of the Common Shares. The Trust may utilize certain strategies, including taking positions in futures or interest rate swaps and forward rate contracts, for the purpose of reducing the interest rate sensitivity of the portfolio and decreasing the Trust's exposure to interest rate risk, although there can be no assurance that it will do so or that such strategies will be successful.

Eaton Vance National Municipal Opportunities Trust 35 Prospectus dated July 22,2021

Because the Trust is managed toward an income objective, it may hold more longer duration or maturity obligations and thereby be more exposed to interest rate risk than municipal income funds that are managed with a greater emphasis on total return. Certain factors, such as the presence of call features, may cause a particular fixed-income security, or the Trust as a whole, to exhibit less sensitivity to changes in interest rates. Certain of the Trust's investments may also be valued, in part, by reference to the relative relationship between interest rates on tax-exempt securities and taxable securities, respectively. When the market for tax-exempt securities underperforms (or outperforms) the market for taxable securities, the value of these investments may be negatively affected (or positively affected). Certain countries and regulatory bodies may use negative interest rates as a monetary policy tool to encourage economic growth during periods of deflation. In a negative interest rate environment, debt instruments may trade at negative yields, which means the purchaser of the instrument may receive at maturity less than the total amount invested.

The income investors receive from the Trust is based primarily on the interest it earns from its investments, which can vary widely over the short- and long-term. If long-term interest rates drop, investors' income from the Trust over time could drop as well if the Trust purchases securities with lower interest coupons.

The Trust invests in residual interest bonds. Compared to similar fixed-rate municipal bonds, the value of these bonds will fluctuate to a greater extent in response to changes in prevailing long-term interest rates. Moreover, the income earned on residual interest municipal bonds will fluctuate in response to changes in prevailing short-term interest rates. Thus, when such bonds are held by the Trust, an increase in short- or long-term market interest rates may adversely affect the income received from such bonds or the NAV of Trust shares.

Call and Reinvestment Risks. If interest rates fall, it is possible that issuers of callable bonds with high interest coupons will 'call' (or prepay) their bonds before their maturity date. If a call were exercised by the issuer during a period of declining interest rates, the Trust would likely replace such called security with a lower yielding security. If that were to happen, it could decrease the Trust's dividends and possibly could affect the market price of Common Shares. Similar risks exist when the Trust invests the proceeds from matured or traded municipal obligations at market interest rates that are below the Trust's current earnings rate.

Credit Risk. Credit risk is the risk that one or more municipal bonds in the Trust's portfolio will decline in price, or fail to pay interest or principal when due, because the issuer of the bond experiences a decline in its financial status. In general, lower rated municipal bonds carry a greater degree of risk that the issuer will lose its ability to make interest and principal payments, which could have a negative impact on the Trust's NAV or dividends. Securities rated in the fourth highest category (i.e., Baa by Moody's or BBB by S&P or Fitch) are considered investment grade quality, but may have speculative characteristics. Municipal obligations may be insured as to principal and interest payments. If the claims paying ability or other rating of the insurer is downgraded by a rating agency, the value of such obligations may be negatively affected. The Trust is also exposed to credit risk when it engages in certain types of derivatives transactions and when it engages in transactions that expose the Trust to counterparty risk. See 'Derivatives Risk.'

Changes in the credit quality of the issuers of municipal obligations held by the Trust will affect the principal value of (and possibly the income earned on) such obligations. The credit quality of an issuer of municipal obligations may be affected by a variety of factors, including the issuer's tax base, the extent to which the issuer relies on federal or state aid, limitations on the taxing power of the issuer and changes in general economic conditions. Changes by Rating Agencies in their ratings of a security and in the ability of the issuer to make payments of principal and interest may also affect the value of the Trust's investments. The amount of information about the financial condition of an issuer of municipal obligations may not be as extensive as that made available by corporations whose securities are publicly traded.

In evaluating the quality of a particular instrument, Eaton Vance may take into consideration, among other things, a credit rating assigned by a credit rating agency, the issuer's financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. Credit rating agencies are private services that provide ratings of the credit quality of certain investments. Credit ratings issued by rating agencies are based on a number of factors including, but not limited to, the issuer's financial condition and the rating agency's credit analysis, if applicable, at the time of rating. As such, the rating assigned to any particular security is not necessarily a reflection of the issuer's current financial condition. The ratings assigned are not absolute standards of credit quality and do not evaluate market risks or necessarily reflect the issuer's current financial condition or the volatility or liquidity of the security.

Eaton Vance National Municipal Opportunities Trust 36 Prospectus dated July 22,2021

For purposes of determining compliance with the Trust's credit quality restrictions, Eaton Vance relies primarily on the ratings assigned by credit rating agencies but may, in the case of unrated instruments, perform its own credit and investment analysis to determine an instrument's credit quality. A credit rating may have a modifier (such as plus, minus or a numerical modifier) to denote its relative status within the rating. The presence of a modifier does not change the security credit rating (for example, BBB- and Baa3 are within the investment grade rating) for purposes of the Trust's investment limitations. If an instrument is rated differently by two or more rating agencies, the highest rating will be used for purposes of the Trust's rating restrictions.

The Trust may invest in unrated obligations for which Eaton Vance will make a credit quality determination for purposes of the Trust's credit quality policy. To the extent that the Trust invests in such unrated obligations, the Trust's credit quality will be more dependent on Eaton Vance's credit analysis than if the Trust invested in only rated obligations.

The Trust may invest in MLOs and certificates of participation. The obligation of the issuer to meet its obligations under such instruments is often subject to the ongoing appropriation by a legislative body, on an annual or other basis, of funds for the payment of the obligations. Investments in municipal leases are thus subject to the risk that the legislative body will not make the necessary appropriation and the issuer will not otherwise be willing or able to meet its obligation.

Liquidity Risk. The secondary market for some municipal obligations is less liquid than that for widely traded taxable debt obligations or widely traded municipal obligations. No established resale market exists for certain of the municipal obligations in which the Trust may invest. The Trust has no limitation on the amount of its assets that may be invested in securities that are not readily marketable or are subject to restrictions on resale. In certain situations, the Trust could find it more difficult to sell such securities at desirable times and/or prices. The Trust may not be able to readily dispose of such securities at prices that approximate those at which the Trust could sell such securities if they were more widely traded or at which the Trust has valued such securities and, as a result of such illiquidity, the Trust may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. In addition, the limited liquidity could affect the market price of the securities, thereby adversely affecting the Trust's NAV and ability to make distributions.

Municipal Bond Market Risk. Investing in the municipal bond market involves certain risks. Certain securities in which the Trust will invest will not be registered with the SEC or any state securities commission and will not be listed on any national securities exchange. The amount of public information available about the municipal obligations in the Trust's portfolio is generally less than for corporate equities or bonds, and the investment performance of the Trust may, therefore, be more dependent on the analytical abilities of Eaton Vance than if the Trust were a stock fund or taxable bond fund.

The ability of municipal issuers to make timely payments of interest and principal may be diminished during general economic downturns and as governmental cost burdens are reallocated among federal, state and local governments. In addition, laws enacted in the future by Congress or state legislatures or referenda could extend the time for payment of principal and/or interest, or impose other constraints on enforcement of such obligations, or on the ability of municipalities to levy taxes. Issuers of municipal obligations might seek protection under the bankruptcy laws. In the event of bankruptcy of an issuer, the Trust could experience delays in collecting principal and interest to which it is entitled, and may obtain only a limited recovery or no recovery in such circumstances. To enforce its rights in the event of default in the payment of interest or repayment of principal, or both, the Trust may take possession of and manage the assets securing the issuer's obligations on such securities, which may increase the Trust's operating expenses. Any income derived from the Trust's ownership or operation of such assets may not be tax-exempt.

The value of municipal securities generally may be affected by uncertainties in the municipal markets as a result of legislation or litigation, including legislation or litigation that changes the taxation of municipal securities or the rights of municipal security holders in the event of a bankruptcy. Certain provisions of the U.S. Bankruptcy Code governing such bankruptcies are unclear. Further, the application of state law to municipal security issuers could produce varying results among the states or among municipal security issuers within a state. These uncertainties could have a significant impact on the prices of the municipal securities in which the Trust invests.

If the number of municipal borrowers and the amount of outstanding municipal securities contract, without corresponding reductions in investor demand for municipal securities, the Trust may have fewer investment alternatives, may invest in securities that it previously would have declined and may concentrate its investments in a smaller number of issuers.

Below Investment Grade Securities Risk. Up to 30% of the Trust's investments in municipal obligations may be, at the time of investment, rated below investment grade or if unrated deemed by the Adviser to be below investment grade. Such obligations are commonly called 'junk bonds' and will have speculative characteristics in varying degrees. While such obligations may have some quality and protective characteristics, these characteristics can be expected to be offset or outweighed by uncertainties or major risk exposures to adverse conditions.

Eaton Vance National Municipal Opportunities Trust 37 Prospectus dated July 22,2021

Below investment grade municipal obligations involve a greater degree of credit, interest rate and market risk than investment grade municipal obligations. Below investment grade municipal obligations are subject to a greater risk of an issuer's inability to meet principal and interest payments on the obligations and may also be subject to greater price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity. Below investment grade municipal obligations are considered predominantly speculative because of the credit risk of their issuers. While offering a greater potential opportunity for capital appreciation and higher yields, below investment grade municipal obligations typically entail greater potential price volatility and may be less liquid than investment grade municipal obligations. Issuers of below investment grade municipal obligations are more likely to default on their payments of interest and principal owed to the Trust, and such defaults will reduce the Trust's NAV and income distributions. The prices of these below investment grade obligations are more sensitive to negative developments than higher rated securities. Adverse economic conditions generally lead to a higher non-payment rate. In addition, below investment grade municipal obligations may lose significant value before a default occurs as the market adjusts to expected higher non-payment rates.

Increases in interest rates and changes in the economy may adversely affect the ability of issuers of lower grade municipal obligations to pay interest and to repay principal, to meet projected financial goals and to obtain additional financing. Issuers of below investment grade municipal obligations may be more adversely affected by a prolonged recession or continued deterioration of economic conditions. In the event that an issuer of securities held by the Trust experiences difficulties in the timely payment of principal or interest and such issuer seeks to restructure the terms of its borrowings, the Trust may incur additional expenses and may determine to invest additional assets with respect to such issuer or the project or projects to which the Trust's portfolio securities relate. Further, the Trust may incur additional expenses to the extent that it is required to seek recovery upon a default in the payment of interest or the repayment of principal on its portfolio holdings, and the Trust may be unable to obtain full recovery thereof. When the Trust invests in lower rated or unrated municipal obligations, the achievement of the Trust's investment objectives is more dependent on the Adviser's credit analysis than would be the case if the Trust were investing in municipal obligations rated investment grade.

To the extent that there is no established market for some of the lower grade municipal obligations in which the Trust may invest, trading in such securities may be relatively inactive. The Adviser is responsible for determining the NAV of the Trust, subject to the supervision of the Trust's Board. During periods of reduced market liquidity and in the absence of readily available market quotations for lower grade municipal obligations held in the Trust's portfolio, the ability of the Adviser to value the Trust's securities becomes more difficult and the Adviser's use of judgment may play a greater role in the valuation of the Trust's securities due to the reduced availability of reliable objective data. The effects of adverse publicity and investor perceptions may be more pronounced for securities for which no established market exists as compared with the effects on securities for which a regular market does exist. Further, the Trust may have more difficulty selling such securities in a timely manner and at their stated value than would be the case for securities for which an established market does exist.

Municipal obligations held by the Trust that are initially rated below investment grade may subsequently be determined by the Adviser to be of investment grade quality for purposes of the Trust's investment policies if the securities subsequently are backed by escrow accounts containing U.S. Government obligations. The Trust may retain in its portfolio an obligation that declines in quality, including defaulted obligations, if such retention is considered desirable by the Adviser. In the case of a defaulted obligation, the Trust may incur additional expense seeking recovery of its investment.

Insurance Risk. Municipal obligations may be insured as to their scheduled payment of principal and interest. Although the insurance feature may reduce some financial risks, the premiums for insurance and the higher market price sometimes paid for insured obligations may reduce the current yield on the insured obligation. Insured obligations also may be secured by bank credit agreements or escrow accounts. Changes in the ratings of an insurer may affect the value of an insured obligation, and in some cases may even cause the value of a security to be less than a comparable uninsured obligation. The insurance does not guarantee the market value of the insured obligation or the net asset value of the Trust's shares. If a municipal obligation is insured, the Trust will use the higher of the Municipal Obligation Rating or the insurance issuer's rating. The obligation of a municipal bond insurance company to pay a claim extends over the life of each insured obligation. Although defaults on insured municipal obligations have been low to date and municipal bond insurers have met their claims, there is no assurance this will continue. A higher than expected default rate could strain the insurer's loss reserves and adversely affect its ability to pay claims to bondholders. Because a significant portion of insured municipal obligations that have been issued and are outstanding is insured by a small number of insurance companies, an event involving one or more of these insurance companies, such as a credit rating downgrade, could have a significant adverse effect on the value of the municipal obligations insured by that insurance company and on the municipal bond markets as a whole.

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Current Regulatory Environment Risk. From time to time proposals have been introduced before Congress for the purpose of restricting or eliminating the federal income tax exemption for interest on certain types of municipal obligations, and it can be expected that similar proposals may be introduced in the future. Any proposed or actual changes in such rates or exempt status, therefore, can significantly affect the demand for and supply, liquidity and marketability of municipal obligations. This could in turn affect the Trust's net asset value and ability to acquire and dispose of municipal obligations at desirable yield and price levels.

The U.S. and non-U.S. derivatives markets have undergone substantial changes in recent years as a result of changes under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the 'Dodd-Frank Act') in the United States and regulation changes in Europe, Asia and other non-U.S. jurisdictions. In particular, the Dodd-Frank Act and related regulations require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. Additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Trust engages in derivative transactions. Trust management cannot predict the effects of any new governmental regulation that may be implemented, and future regulation may impair the effectiveness of the Trust's derivative transactions and its ability to achieve its investment objectives.

At any time after the date of this prospectus, legislation may be enacted that could negatively affect the assets of the Trust. Legislation or regulation may change the way in which the Trust itself is regulated. The Adviser cannot predict the effects of any new governmental regulation that may be implemented, and there can be no assurance that any new governmental regulation will not adversely affect the Trust's ability to achieve its investment objectives.

State Specific Risk. If the Trust focuses its investments in any one state (or U.S. territory), the Trust may be more susceptible to adverse economic, political or regulatory occurrences affecting a particular state (or territory). Certain municipal bond issuers in Puerto Rico have recently experienced financial difficulties and rating agency downgrades, and two such issuers have defaulted on their payment obligations.

Up to 5% of the Trust's investments in municipal obligations may be collateralized by the proceeds from class action or other litigation against the tobacco industry. Such municipal obligations are backed solely by expected revenues to be derived from lawsuits involving tobacco-related deaths and illnesses which were settled between certain states and American tobacco companies. Tobacco settlement bonds are secured by an issuing state's proportionate share in the Master Settlement Agreement ('MSA'). The MSA is an agreement, reached out of court in November 1998 between 46 states and nearly all of the major U.S. tobacco manufacturers. Under the terms of the MSA, the actual amount of future settlement payments by tobacco manufacturers is dependent on many factors, including, but not limited to, annual domestic cigarette shipments, reduced cigarette consumption, increased taxes on cigarettes, inflation, financial capability of tobacco companies, continuing litigation and the possibility of tobacco manufacturer bankruptcy. Payments made by tobacco manufacturers could be negatively impacted if the decrease in tobacco consumption is significantly greater than the forecasted decline. See 'State Specific Investments' in the SAI for additional information about tobacco settlement bonds and the MSA.

Residual Interest Bond Risk. Residual interest bonds are residual interests of a SPV that holds municipal obligations. Residual interest bonds pay interest at rates that vary inversely with changes in prevailing short-term tax-exempt interest rates and provide the economic effect of leverage. The interest rate payable on a residual interest bond also bears an inverse relationship to the interest rate on floating rate notes issued by the SPV ('Floating Rate Notes'). Because changes in the interest rate on the Floating Rate Notes inversely affect the interest paid on the residual interest bond, the value and income of a residual interest bond is generally more volatile than that of a fixed rate bond. Residual interest bonds have interest rate adjustment formulas that generally reduce or, in the extreme, eliminate the interest paid to the Trust when short-term interest rates rise, and increase the interest paid to the Trust when short-term interest rates fall. Residual interest bonds have varying degrees of liquidity, and the market for these securities is relatively volatile. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. Although volatile, residual interest bonds typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. These securities usually permit the investor to convert the floating rate to a fixed rate (normally adjusted downward), and this optional conversion feature may provide a partial hedge against rising rates if exercised at an opportune time. While residual interest bonds expose the Trust to leverage risk because they provide two or more dollars of bond market exposure for every dollar invested, they are not subject to the Trust's restrictions on borrowings.

Any economic effect of leverage through the Trust's purchase of residual interest bonds will create an opportunity for increased Common Share net income and returns, but will also create the possibility that the Trust's long-term returns will be diminished if the cost of leverage exceeds the return on the bonds purchased with leverage by the Trust. The amount of fees paid to Eaton Vance for investment advisory services will be higher if the Trust uses financial leverage because

Eaton Vance National Municipal Opportunities Trust 39 Prospectus dated July 22,2021

the fees will be calculated based on the Trust's average daily gross assets, which may create a conflict of interest between Eaton Vance and the Common Shareholders. 'Gross assets' of the Trust means the total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage. See 'Investment Objectives, Policies and Risks - Risk Considerations - Leverage Risk.'

A SPV typically can be collapsed or closed by the holder of the residual interest bonds (such as the Trust) or by the liquidity provider. In certain circumstances, the Trust may enter into shortfall and forbearance agreements with respect to a residual interest bond. The Trust generally may enter into such agreements (i) when the liquidity provider to the SPV requires such an agreement because the level of leverage in the SPV exceeds the level that the liquidity provider is willing support absent such an agreement; and/or (ii) to seek to prevent the liquidity provider from collapsing the SPV in the event that the municipal obligation held in the SPV has declined in value. Such agreements commit the Trust to reimburse, upon the termination of the SPV, the difference between the liquidation value of the underlying security (which is the basis of the inverse floater) and the principal amount due to the holders of the floating rate security issued in conjunction with the inverse floater. Such agreements may expose the Trust's other assets to losses. Absent a shortfall and forbearance agreement, the Trust would not be required to make such a reimbursement. If the Trust chooses not to enter into such an agreement, the inverse floater could be terminated and the Trust could incur a loss. Consistent with SEC staff guidance, the Trust will segregate or earmark liquid assets with its custodian on a mark-to-market basis to cover any such payment obligations to liquidity providers.

On December 10, 2013, five U.S. federal agencies published final rules implementing section 619 of the Dodd-Frank Wall Street Reform and Consumer Protection Act (the 'Volcker Rule'). The Volcker Rule prohibits banking entities from engaging in proprietary trading of certain instruments and limits such entities' investments in, and relationships with, covered funds, as defined in the rules. The Volcker Rule precludes banking entities and their affiliates from (i) sponsoring residual interest bond programs as presently structured and (ii) continuing relationships with or services for existing residual interest bond programs. The effects of the Volcker Rule may make it more difficult for the Trust to maintain current or desired levels of income.

Risks of MLOs and Certificates of Participation. The Trust may invest in MLOs and certificates of participation that involve special risks not normally associated with general obligations or revenue obligations. A MLO is a bond that is secured by lease payments made by the party, typically a state or municipality, leasing the facilities (e.g., schools or office buildings) that were financed by the bond. Such lease payments may be subject to annual appropriation or may be made only from revenues associated with the facility financed. In other cases, the leasing state or municipality is obligated to appropriate funds from its general tax revenues to make lease payments as long as it utilizes the leased property. A certificate of participation (also referred to as a 'participation') in a municipal lease is an instrument evidencing a pro rata share in a specific pledged revenue stream, usually lease payments by the issuer . The issuer's obligations under such instruments are often subject to the ongoing appropriation by a legislative body, on an annual or other basis, of funds for the payment thereof. Investments in MLOs and certificates of participation are therefore typically subject to the risk that the legislative body will not make the necessary annual appropriation and the issuer will not otherwise be willing or able to meet its obligation.

Inflation Risk/Deflation Risk. Inflation risk is the risk that the value of assets or income from investment will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Common Shares and distributions thereon can decline. In addition, during periods of rising inflation, short-term interest rates and the Trust's cost of leverage would likely increase, reducing returns to Common Shareholders to the extent that such increased cost is not offset by commensurately higher income. Deflation risk is the risk that prices throughout the economy decline over time − the opposite of inflation. Deflation may have an adverse affect on the creditworthiness of issuers and may make issuer defaults more likely, which may result in a decline in the value of the Trust's investments.

Leverage Risk. The Trust will not utilize leverage in excess of 15% of its gross assets. As discussed above, the Trust currently uses leverage created by investing in residual interest bonds. The Trust will comply with the asset segregation requirements of the 1940 Act in making such investments. Residual interest bonds are securities that pay interest at rates that vary inversely with changes in prevailing short-term interest rates and provide the economic effect of leverage. Although the Trust has no current intention to do so, the Trust is authorized to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act. There can be no assurance that a leveraging strategy will be successful during any period in which it is employed.

The Adviser anticipates that the use of leverage (from residual interest bonds) may result in higher income to Common Shareholders over time. Leverage creates risks for Common Shareholders, including the likelihood of greater volatility of NAV and market price of the Common Shares and the risk that fluctuations in the costs of leverage may affect the return to Common Shareholders. To the extent the income derived from investments purchased with funds received from

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leverage exceeds the cost of leverage, the Trust's distributions will be greater than if leverage had not been used. Conversely, if the income from the investments purchased with such funds is not sufficient to cover the cost of leverage, the amount available for distribution to Common Shareholders will be less than if leverage had not been used. In the latter case, Eaton Vance, in its best judgment, may nevertheless determine to maintain the Trust's leveraged position if it deems such action to be appropriate. There can be no assurance that a leveraging strategy will be successful.

As discussed under 'Management of the Trust,' the investment advisory fee paid to Eaton Vance is calculated on the basis of the Trust's average daily gross assets. 'Gross assets' of the Trust shall mean total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. This means that the Trust's advisory fees will be higher when leverage is utilized which may create an incentive for the Adviser to employ leverage. In this regard, holders of any preferred shares do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds of the use of leverage, which means that Common Shareholders effectively bear the entire advisory fee.

Financial leverage may also be achieved through the purchase of certain derivative instruments. The Trust's use of derivative instruments exposes the Trust to special risks. See 'Investment Objectives, Policies and Risks - Additional Investment Practices' and 'Investment Objectives, Policies and Risks - Additional Risk Considerations.'

Derivatives Risk. In addition to investing in residual interest bonds, the Trust may invest without limitation in other derivative instruments (which are instruments that derive their value from a reference instrument) acquired for hedging purposes or investment purposes, such as financial futures contracts and related options, interest rate, total return and other swaps and forward rate contracts. Depending on the type of derivative instrument and the Trust's investment strategy, a reference instrument could be a security, instrument, index, currency, commodity, economic indicator or event ('reference instruments'). The loss on derivative instruments (other than purchased options) may substantially exceed amounts invested in these instruments. Derivative transactions, including options on securities and securities indices and other transactions in which the Trust may invest may subject the Trust to increased risk of principal loss due to unexpected movements in securities prices and interest rates, and imperfect correlations between the Trust's securities holdings and indices upon which derivative transactions are based. Derivatives can be illiquid, may disproportionately increase losses, and may have a potentially large impact on the Trust's performance. Use of derivative instruments may cause the realization of higher amounts of short-term capital gains (generally taxed at ordinary income tax rates) than if such instruments had not been used. Trust obligations created pursuant to derivative instruments may give rise to leverage, which would subject the Trust to increased leverage risk. The Trust also will be subject to credit risk with respect to the counterparties to any OTC derivatives contracts entered into by the Trust. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Trust may experience significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Trust may obtain only a limited recovery or no recovery in such circumstances.

The use of derivatives to enhance income is considered to be speculative in nature. The use of derivatives may result in greater losses than if they had not been used, may require the Trust to sell or purchase portfolio investments at inopportune times or for prices other than current market value, may limit the amount of appreciation the Trust can realize on an investment or may cause the Trust to hold a security it might otherwise sell. Segregated liquid assets, amounts paid by the Trust as premiums and cash or other assets held in margin accounts with respect to derivatives transactions are not otherwise available to the Trust for investment or operational purposes. Certain derivative transactions may have economic characteristics similar to leverage. See 'Additional Risk Considerations - Leverage Risk.'

The U.S. and non-U.S. derivatives markets have undergone substantial changes in recent years as a result of changes under the Dodd-Frank Act in the United States and regulation changes in Europe, Asia and other non-U.S. jurisdictions. In particular, the Dodd-Frank Act and related regulations require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. As of October 28, 2020, the SEC has adopted new regulations that may significantly alter the Trust's regulatory obligations with regard to its derivatives usage. In particular, the new regulations will, upon implementation, eliminate the current asset segregation framework for covering derivatives and certain other financial instruments, impose new responsibilities on the Board and establish new reporting and recordkeeping requirements for the Trust and may, depending on the extent to which the Trust uses derivatives, impose value at risk limitations on the Trust's use of derivatives, and require the Trust's Board to adopt a derivative risk management program. The implementation of these requirements may limit the ability of the Trust to use derivative instruments as part of its investment strategy, increase the costs of using these instruments or

Eaton Vance National Municipal Opportunities Trust 41 Prospectus dated July 22,2021

make them less effective. Additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Trust engages in derivative transactions. Trust management cannot predict the effects of any new governmental regulation that may be implemented, and there can be no assurance that any new government regulation will not adversely affect the Trust's performance or ability to achieve its investment objectives.

Counterparty Risk. Changes in the credit quality of the companies that serve as the Trust's counterparties with respect to its derivatives positions and liquidity providers for the Trust's residual interest bonds or other investments supported by another party's credit will affect the value of those instruments. Certain entities that have served as counterparties in the municipals markets have in the past incurred significant financial hardships including bankruptcy and material loss of credit standing as a result of exposure to investments that have experienced defaults or otherwise suffered extreme credit deterioration. As a result, such hardships reduced these entities' capital and called into question their continued ability to perform their obligations. By using derivatives or other instruments that expose the Trust to counterparties, the Trust assumes the risk that its counterparties could experience future financial hardship.

The counterparty risk for cleared derivatives is generally lower than for uncleared over-the-counter derivative transactions since generally a clearing organization becomes substituted for each counterparty to a cleared derivative contract and, in effect, guarantees the parties' performance under the contract as each party to a trade looks only to the clearing organization for performance of financial obligations under the derivative contract. However, there can be no assurance that a clearing organization, or its members, will satisfy its obligations to the Trust.

Tax Risk. The value of the Trust's investments and its NAV may be adversely affected by changes in tax rates and policies. Because interest income from municipal obligations normally is not subject to regular federal income taxation, the attractiveness of municipal obligations in relation to other investment alternatives is affected by changes in federal income tax rates or changes in the tax-exempt status of interest income from municipal obligations. From time to time proposals have been introduced before Congress for the purpose of restricting or eliminating the federal income tax exemption for interest on certain types of municipal obligations, and it can be expected that similar proposals may be introduced in the future. Any proposed or actual changes in such rates or exempt status, therefore, can significantly affect the demand for and supply, liquidity and marketability of municipal obligations. This could, in turn, affect the Trust's NAV and ability to acquire and dispose of municipal obligations at desirable yield and price levels. The Trust is not a suitable investment for individual retirement accounts, for other tax-exempt or tax-deferred accounts or for investors who are otherwise indifferent to the federal income tax consequences of their investments. See 'Distributions' and 'Federal income tax matters.'

The Trust will invest in municipal obligations in reliance at the time of purchase on an opinion of bond counsel to the issuer that the interest paid on those securities will be excludable from gross income under the regular federal income tax, and the Adviser will typically not independently verify that opinion. Subsequent to the Trust's acquisition of such a municipal security, however, the security may be determined to pay, or to have paid, taxable income. As a result, the treatment of dividends previously paid or to be paid by the Trust as 'exempt-interest dividends' could be adversely affected, subjecting the Trust's Common Shareholders to increased federal income tax liabilities.

Interest income from certain types of municipal obligations may be a tax preference item for purposes of the AMT for individual investors.

Futures Risk. Although some futures contracts call for making or taking delivery of the underlying reference instrument, generally these obligations are closed out prior to delivery by offsetting purchases or sales of matching futures contracts (same exchange, underlying security or index, and delivery month). Closing a futures contract sale is effected by purchasing a futures contract for the same aggregate amount of the specific type of financial instrument or commodity with the same delivery date. If an offsetting purchase price is less than the original sale price, the Trust realizes a capital gain, or if it is more, the Trust realizes a capital loss. Conversely, if an offsetting sale price is more than the original purchase price, the Trust realizes a capital gain, or if it is less, the Trust realizes a capital loss. The Adviser has claimed an exclusion from the definition of a Commodity Pool Operator ('CPO') under the Commodity Exchange Act with respect to the Trust and therefore, neither the Adviser nor the Trust are subject to registration or regulation thereunder.

Management Risk. The Trust is subject to management risk because it is actively managed. Eaton Vance and the individual portfolio managers invest the assets of the Trust as they deem appropriate in implementing the Trust's investment strategy. Accordingly, the success of the Trust depends upon the investment skills and analytical abilities of Eaton Vance and the individual portfolio managers to develop and effectively implement strategies that achieve the Trust's investment objectives. There is no assurance that Eaton Vance and the individual portfolio managers will be successful in developing and implementing the Trust's investment strategy. Subjective decisions made by Eaton Vance and the individual portfolio managers may cause the Trust to incur losses or to miss profit opportunities.

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Recent Market Conditions. An outbreak of respiratory disease caused by a novel coronavirus was first detected in China in late 2019 and subsequently spread internationally. This coronavirus has resulted in closing borders, enhanced health screenings, changes to healthcare service preparation and delivery, quarantines, cancellations, disruptions to supply chains and customer activity, as well as general concern and uncertainty. The impact of this coronavirus has resulted in a substantial economic downturn, which may continue for an extended period of time. Health crises caused by outbreaks of disease, such as the coronavirus outbreak, may exacerbate other pre-existing political, social and economic risks and disrupt normal market conditions and operations. The impact of this outbreak has negatively affected the worldwide economy, as well as the economies of individual countries and industries, and could continue to affect the market in significant and unforeseen ways. Other epidemics and pandemics that may arise in the future may have similar effects. For example, a global pandemic or other widespread health crisis could cause substantial market volatility and exchange trading suspensions and closures. In addition, the increasing interconnectedness of markets around the world may result in many markets being affected by events or conditions in a single country or region or events affecting a single or small number of issuers. The coronavirus outbreak and public and private sector responses thereto have led to large portions of the populations of many countries working from home for indefinite periods of time, temporary or permanent layoffs, disruptions in supply chains, and lack of availability of certain goods. The impact of such responses could adversely affect the information technology and operational systems upon which the Trust and the Trust's service providers rely, and could otherwise disrupt the ability of the employees of the Trust's service providers to perform critical tasks relating to the Trust. Any such impact could adversely affect the Trust's performance, or the performance of the securities in which the Trust invests and may lead to losses on your investment in the Trust.

Cybersecurity Risk. With the increased use of technologies by Trust service providers to conduct business, such as the Internet, the Trust is susceptible to operational, information security and related risks. The Trust relies on communications technology, systems, and networks to engage with clients, employees, accounts, shareholders, and service providers, and a cyber incident may inhibit the Trust's ability to use these technologies. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber attacks include, but are not limited to, gaining unauthorized access to digital systems (e.g., through 'hacking' or malicious software coding) for purposes of misappropriating assets or sensitive information, corrupting data, or causing operational disruption. Cyber attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites. A denial-of-service attack is an effort to make network services unavailable to intended users, which could cause shareholders to lose access to their electronic accounts, potentially indefinitely. Employees and service providers also may not be able to access electronic systems to perform critical duties for the Trust, such as trading and NAV calculation, during a denial-of-service attack. There is also the possibility for systems failures due to malfunctions, user error and misconduct by employees and agents, natural disasters, or other foreseeable and unforeseeable events.

Because technology is consistently changing, new ways to carry out cyber attacks are always developing. Therefore, there is a chance that some risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the Trust's ability to plan for or respond to a cyber attack. Like other Trusts and business enterprises, the Trust and its service providers have experienced, and will continue to experience, cyber incidents consistently. In addition to deliberate cyber attacks, unintentional cyber incidents can occur, such as the inadvertent release of confidential information by the Trust or its service providers.

The Trust uses third party service providers who are also heavily dependent on computers and technology for their operations. Cybersecurity failures or breaches by the Trust's investment adviser or administrator and other service providers (including, but not limited to, the custodian or transfer agent), and the issuers of securities in which the Trust invests, may disrupt and otherwise adversely affect their business operations. This may result in financial losses to the Trust, impede Trust trading, interfere with the Trust's ability to calculate its NAV, or cause violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, litigation costs, or additional compliance costs. While many of the Trust service providers have established business continuity plans and risk management systems intended to identify and mitigate cyber attacks, there are inherent limitations in such plans and systems including the possibility that certain risks have not been identified. The Trust cannot control the cybersecurity plans and systems put in place by service providers to the Trust and issuers in which the Trust invests. The Trust and its shareholders could be negatively impacted as a result.

Other Investment Companies Risk. The Trust may, subject to the limitations of the 1940 Act, invest in the securities of other investment companies. Such securities may be leveraged. As a result, the Trust may be indirectly exposed to leverage through an investment in such securities. Utilization of leverage is a speculative investment technique and involves certain risks. The Trust, as a holder of the securities of other investment companies, will bear its pro rata portion of the other investment companies' expenses, including advisory fees. These expenses are in addition to the direct expenses of the Trust's own operations.

Eaton Vance National Municipal Opportunities Trust 43 Prospectus dated July 22,2021

Market Disruption. Global instability, war, geopolitical tensions and terrorist attacks in the United States and around the world have previously resulted, and may in the future result in market volatility and may have long-term effects on the United States and worldwide financial markets and may cause further economic uncertainties in the United States and worldwide. The Trust cannot predict the effects of significant future events on the global economy and securities markets. A similar disruption of the financial markets could impact interest rates, auctions, secondary trading, ratings, credit risk, inflation and other factors relating to the Common Shares.

Swaps Risk. Swap agreements are two-party contracts entered into primarily by institutional investors for periods ranging from a few weeks to more than one year. In a standard 'swap' transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on a particular predetermined reference instrument or instruments, which can be adjusted for an interest rate factor. The gross returns to be exchanged or 'swapped' between the parties are generally calculated with respect to a 'notional amount' (i.e., the return on or increase in value of a particular dollar amount invested at a particular interest rate or in a 'basket' of securities representing a particular index). Other types of swap agreements may calculate the obligations of the parties to the agreement on a 'net basis.' Consequently, a party's current obligations (or rights) under a swap agreement will generally be equal only to the net amount to be paid or received under the agreement based on the relative values of the positions held by each party to the agreement (the 'net amount'). Whether the use of swap agreements will be successful will depend on the Adviser's ability to predict correctly whether certain types of reference instruments are likely to produce greater returns than other instruments. Swap agreements may be subject to contractual restrictions on transferability and termination and they may have terms of greater than seven days. The Trust's obligations under a swap agreement will be accrued daily (offset against any amounts owed to the Trust under the swap). Developments in the swaps market, including potential government regulation, could adversely affect the Trust's ability to terminate existing swap agreements or to realize amounts to be received under such agreements, as well as to participate in swap agreements in the future. If there is a default by the counterparty to a swap, the Trust will have contractual remedies pursuant to the swap agreement, but any recovery may be delayed depending on the circumstances of the default.

Duration and Maturity Risk. Holding long duration and long maturity investments will expose the Trust to certain magnified risks. These risks include interest rate risk, credit risk and liquidity risks as discussed above.

Hedging Risk. The Trust's use of derivatives or other transactions to reduce risks involves costs and will be subject to Eaton Vance's ability to predict correctly changes in the relationships of such hedge instruments to the Trust's portfolio holdings or other factors. No assurance can be given that Eaton Vance's judgment in this respect will be correct. In addition, no assurance can be given that the Trust will enter into hedging or other transactions at times or under circumstances in which it may be advisable to do so. Hedging transactions have risks, including the imperfect correlation between the value of such instruments and the underlying assets of the Trust, which creates the possibility that the loss on such instruments may be greater than the gain, if any, in the value of the underlying asset in the Trust's portfolio; the limited availability of such instruments; the loss of principal; the possible default of the other party to the transaction; illiquidity of the derivative investments; and the imperfect correlation between the tax-exempt and taxable markets. Furthermore, the ability to successfully use hedging transactions depends on the Eaton Vance's ability to predict pertinent market movements, which cannot be assured. Thus, the use of hedging transactions may result in losses greater than if they had not been used, may require the Trust to sell or purchase portfolio investments at inopportune times or for prices other than current market values, may limit the amount of appreciation the Trust can realize on an investment, or may cause the Trust to hold a security that it might otherwise sell.

Anti-takeover Provisions. The Trust's Agreement and Declaration of Trust (the 'Declaration of Trust') and Amended and Restated By-Laws (the 'By-Laws' and together with the Declaration of Trust, the 'Organizational Documents') include provisions that could have the effect of limiting the ability of other persons or entities to acquire control of the Trust or to change the composition of its Board. For example, pursuant to the Trust's Declaration of Trust, the Board is divided into three classes of Trustees with each class serving for a three-year term and certain types of transactions require the favorable vote of holders of at least 75% of the outstanding shares of the Trust. See 'Description of Capital Structure - Certain Provisions of the Organizational Documents - Anti-Takeover Provisions in the Organizational Documents.'

Management of the Trust

BOARD OF TRUSTEES

The management of the Trust, including general supervision of the duties performed by the Adviser under the Advisory Agreement (as defined below), is the responsibility of the Trust's Board under the laws of The Commonwealth of Massachusetts and the 1940 Act.

Eaton Vance National Municipal Opportunities Trust 44 Prospectus dated July 22,2021

THE ADVISER

Eaton Vance acts as the Trust's investment adviser under an Investment Advisory and Administrative Agreement (the 'Advisory Agreement'). Eaton Vance has offices at Two International Place, Boston, MA 02110. Eaton Vance and its predecessor organizations have been managing assets since 1924 and managing investment funds since 1931. Prior to March 1, 2021, Eaton Vance was a wholly owned subsidiary of Eaton Vance Corp. ('EVC').

On March 1, 2021, Morgan Stanley acquired EVC (the 'Transaction') and Eaton Vance became an indirect, wholly owned subsidiary of Morgan Stanley. In connection with the Transaction, the Trust entered into a new investment advisory and administrative agreement with Eaton Vance. The agreement was approved by shareholders prior to the consummation of the Transaction and was effective upon its closing.

Effective March 1, 2021, any fee reduction agreement previously applicable to the Trust was incorporated into its new investment advisory and administrative agreement with Eaton Vance.

Morgan Stanley (NYSE: MS), whose principal offices are at 1585 Broadway, New York, New York 10036, is a preeminent global financial services firm engaged in securities trading and brokerage activities, as well as providing investment banking, research and analysis, financing and financial advisory services. As of March 31, 2021, Morgan Stanley's asset management operations had aggregate assets under management of approximately $1.4 trillion.

Under the general supervision of the Trust's Board, Eaton Vance is responsible for managing the Trust's overall investment program, determining the Trust's allocations among its permitted investments, and selecting individual holdings. The Adviser will furnish to the Trust investment advice and office space and all necessary office facilities, equipment and personnel for servicing the investments of the Trust and for administering its affairs. The Adviser will compensate all Trustees and officers of the Trust who are members of the Adviser's organization and will also compensate all other Adviser personnel who provide research and investment services to the Trust. Pursuant to the Advisory Agreement, the Trust pays the Adviser a fee calculated as a percentage of the Trust's average daily gross assets in return for these investment advisory services, facilities and payments. The Trust's advisory fee currently is computed at an annual rate of 0.60% of the Trust's average daily gross assets up to and including $1.5 billion and 0.59% of average daily gross assets over $1.5 billion. For purposes of this calculation, 'gross assets' of the Trust shall mean total assets of the Trust, including any form of investment leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to investment leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means, all as determined in accordance with generally accepted accounting principles.)

During any periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust's gross assets, including any form of investment leverage. As demonstrated in the fee table under 'Summary of Trust Expenses,' after giving effect to the Trust's use of leverage and using the assumptions set forth in the fee table, the management fee would be 0.64%.

Cynthia J. Clemson is responsible for the overall and day-to-day management of the Trust's investments. Ms. Clemson is a Vice President of Eaton Vance, is Co-Director of the Municipal Investments Group and has been a portfolio manager of the Trust since May 2009. She has managed other Eaton Vance portfolios for more than five years.

Additional Information Regarding Portfolio Managers

The SAI provides additional information about the portfolio managers' compensation, other accounts managed by the portfolio managers, and the portfolio managers' ownership of securities in the Trust. The SAI is available free of charge by calling 1-800-262-1122 or by visiting the Trust's website at http://www.eatonvance.com. The information contained in, or that can be accessed through, the Trust's website is not part of this Prospectus or the SAI.

The Trust and the Adviser have adopted codes of ethics relating to personal securities transactions (the 'Code of Ethics'). The Codes of Ethics permit Adviser personnel to invest in securities (including securities that may be purchased or held by the Trust) for their own accounts, subject to the provisions of the Codes of Ethics and certain employees are also subject to certain pre-clearance, reporting and other restrictions and procedures contained in such Codes of Ethics.

The Trust's annual shareholder report contains information regarding the basis for the Trustees' approval of the Trust's Advisory Agreement.

Eaton Vance National Municipal Opportunities Trust 45 Prospectus dated July 22,2021

THE ADMINISTRATOR

Eaton Vance serves as administrator of the Trust. Under the Advisory Agreement, Eaton Vance has been engaged to administer the Trust's affairs, subject to the supervision of the Board, and shall furnish office space and all necessary office facilities, equipment and personnel for administering the affairs of the Trust.

In addition to the advisory fee, the Trust pays all costs and expenses of its operation, including compensation of its Trustees (other than those affiliated with the Adviser), custodial expenses, dividend disbursing expenses, legal fees, expenses of independent auditors, expenses of preparing Trust documents and reports to governmental agencies, and taxes and filing or other fees, if any.

Plan of Distribution

The Trust may sell the Common Shares being offered under this Prospectus in any one or more of the following ways: (i) directly to purchasers; (ii) through agents; (iii) to or through underwriters; or (iv) through dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale.

The Trust may distribute Common Shares from time to time in one or more transactions at: (i) a fixed price or prices that may be changed; (ii) market prices prevailing at the time of sale; (iii) prices related to prevailing market prices; or (iv) negotiated prices; provided, however, that in each case the offering price per Common Share (less any underwriting commission or discount) must equal or exceed the NAV per Common Share.

The Trust from time to time may offer its Common Shares through or to certain broker-dealers, including UBS Securities LLC, that have entered into selected dealer agreements relating to at-the-market offerings.

The Trust may directly solicit offers to purchase Common Shares, or the Trust may designate agents to solicit such offers. The Trust will, in a Prospectus Supplement relating to such Offering, name any agent that could be viewed as an underwriter under the 1933 Act, and describe any commissions the Trust must pay to such agent(s). Any such agent will be acting on a reasonable best efforts basis for the period of its appointment or, if indicated in the applicable Prospectus Supplement or other offering materials, on a firm commitment basis. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for the Trust in the ordinary course of business.

If any underwriters or agents are used in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will enter into an underwriting agreement or other agreement with them at the time of sale to them, and the Trust will set forth in the Prospectus Supplement relating to such Offering their names and the terms of the Trust's agreement with them.

If a dealer is utilized in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will sell such Common Shares to the dealer, as principal. The dealer may then resell such Common Shares to the public at varying prices to be determined by such dealer at the time of resale.

The Trust may engage in at-the-market offerings to or through a market maker or into an existing trading market, on an exchange or otherwise, in accordance with Rule 415(a)(4) under the 1933 Act. An at-the-market offering may be through an underwriter or underwriters acting as principal or agent for the Trust.

Agents, underwriters and dealers may be entitled under agreements which they may enter into with the Trust to indemnification by the Trust against certain civil liabilities, including liabilities under the 1933 Act, and may be customers of, engage in transactions with or perform services for the Trust in the ordinary course of business.

In order to facilitate the Offering of Common Shares, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of Common Shares or any other Common Shares the prices of which may be used to determine payments on the Common Shares. Specifically, any underwriters may over-allot in connection with the Offering, creating a short position for their own accounts. In addition, to cover over-allotments or to stabilize the price of Common Shares or of any such other Common Shares, the underwriters may bid for, and purchase, Common Shares or any such other Common Shares in the open market. Finally, in any Offering of Common Shares through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing Common Shares in the Offering if the syndicate repurchases previously distributed Common Shares in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of Common Shares above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

Eaton Vance National Municipal Opportunities Trust 46 Prospectus dated July 22,2021

The Trust may enter into derivative transactions with third parties, or sell Common Shares not covered by this Prospectus to third parties in privately negotiated transactions. If the applicable Prospectus Supplement indicates, in connection with those derivatives, the third parties may sell Common Shares covered by this Prospectus and the applicable Prospectus Supplement or other offering materials, including in short sale transactions. If so, the third parties may use Common Shares pledged by the Trust or borrowed from the Trust or others to settle those sales or to close out any related open borrowings of securities, and may use Common Shares received from the Trust in settlement of those derivatives to close out any related open borrowings of securities. The third parties in such sale transactions will be underwriters and, if not identified in this Prospectus, will be identified in the applicable Prospectus Supplement or other offering materials (or a post-effective amendment).

The maximum amount of compensation to be received by any member of the Financial Industry Regulatory Authority, Inc. will not exceed 8% of the initial gross proceeds from the sale of any security being sold with respect to each particular Offering of Common Shares made under a single Prospectus Supplement.

Any underwriter, agent or dealer utilized in the initial Offering of Common Shares will not confirm sales to accounts over which it exercises discretionary authority without the prior specific written approval of its customer.

Distributions

The Trust intends to make regular monthly cash distributions to Common Shareholders. The amount of each monthly distribution will vary depending on a number of factors, including distributions payable on any preferred shares or other costs of financial leverage. As portfolio and market conditions change, the rate of distribution on the Common Shares and the Trust's distribution policy could change. Over time, the Trust will distribute all of its net investment income (after it pays accrued distributions on any outstanding preferred shares or other costs of financial leverage).

The net investment income of the Trust will consist of all interest income accrued on portfolio investments, short-term capital gain (including short-term gains on options, futures and forward positions and gains on the sale of portfolio investments held for one year or less) in excess of long-term capital loss and income from certain hedging transactions, less all expenses of the Trust. Expenses of the Trust will be accrued each day. Substantially all of the Trust's investment company taxable income will be distributed each year. In addition, at least annually, the Trust intends to distribute any net capital gain (which is the excess of net long-term capital gain over net short-term capital loss). To the extent that the Trust's net investment income and net capital gain for any year exceed the total monthly distributions paid during the year, the Trust will make a special distribution at or near year-end of such excess amount as may be required. If the Trust's total monthly distributions in any year exceed the amount of its net investment income and net capital gain for the year, any such excess would be characterized as a return of capital for federal income tax purposes. A return of capital is treated as a non-dividend distribution for tax purposes and is not subject to current tax. A return of capital reduces a Shareholder's tax cost basis in Trust shares. Under the 1940 Act, for any distribution that includes amounts from sources other than net income, the Trust is required to provide Common Shareholders a written statement regarding the components of such distribution. Such a statement will be provided at the time of any distribution believed to include any such amounts.

Common Shareholders may automatically reinvest some or all of their distributions in additional Common Shares pursuant to the Trust's dividend reinvestment plan. See 'Dividend reinvestment plan.'

Potential Conflicts of Interest

As a diversified global financial services firm, Morgan Stanley, the parent company of the investment adviser, engages in a broad spectrum of activities, including financial advisory services, investment management activities, lending, commercial banking, sponsoring and managing private investment funds, engaging in broker-dealer transactions and principal securities, commodities and foreign exchange transactions, research publication and other activities. In the ordinary course of its business, Morgan Stanley is a full service investment banking and financial services firm and therefore engages in activities where Morgan Stanley's interests or the interests of its clients may conflict with the interests of a Fund or Portfolio, as applicable (collectively, for purposes of this section, 'Fund' or 'Funds'). Morgan Stanley advises clients and sponsors, manages or advises other investment funds and investment programs, accounts and businesses (collectively, together with any new or successor funds, programs, accounts or businesses, the ''Affiliated Investment Accounts'') with a wide variety of investment objectives that in some instances may overlap or conflict with a Fund's investment objectives and present conflicts of interest. In addition, Morgan Stanley may also from time to time create new or successor Affiliated Investment Accounts that may compete with a Fund and present similar conflicts of interest. The discussion below enumerates certain actual, apparent and potential conflicts of interest. There is no assurance that conflicts of interest will be resolved in favor of Fund shareholders and, in fact, they may not be. Conflicts of interest not described below may also exist.

Eaton Vance National Municipal Opportunities Trust 47 Prospectus dated July 22,2021

For more information about conflicts of interest, see the section entitled 'Potential Conflicts of Interest' in the SAI.

Material Non-public Information. It is expected that confidential or material non-public information regarding an investment or potential investment opportunity may become available to the investment adviser. If such information becomes available, the investment adviser may be precluded (including by applicable law or internal policies or procedures) from pursuing an investment or disposition opportunity with respect to such investment or investment opportunity. Morgan Stanley has established certain information barriers and other policies to address the sharing of information between different businesses within Morgan Stanley. In limited circumstances, however, including for purposes of managing business and reputational risk, and subject to policies and procedures and any applicable regulations, Morgan Stanley personnel, including personnel of the investment adviser, on one side of an information barrier may have access to information and personnel on the other side of the information barrier through 'wall crossings.' The investment adviser faces conflicts of interest in determining whether to engage in such wall crossings. Information obtained in connection with such wall crossings may limit or restrict the ability of the investment adviser to engage in or otherwise effect transactions on behalf of the Trust(s) (including purchasing or selling securities that the investment adviser may otherwise have purchased or sold for a Fund in the absence of a wall crossing).

Investments by Morgan Stanley and its Affiliated Investment Accounts. In serving in multiple capacities to Affiliated Investment Accounts, Morgan Stanley, including the investment adviser and its investment teams, may have obligations to other clients or investors in Affiliated Investment Accounts, the fulfillment of which may not be in the best interests of a Fund or its shareholders. A Fund's investment objectives may overlap with the investment objectives of certain Affiliated Investment Accounts. As a result, the members of an investment team may face conflicts in the allocation of suitable investment opportunities among a Fund and other investment funds, programs, accounts and businesses advised by or affiliated with the investment adviser. Certain Affiliated Investment Accounts may provide for higher management or incentive fees or greater expense reimbursements or overhead allocations, all of which may contribute to this conflict of interest and create an incentive for the investment adviser to favor such other accounts. To seek to reduce potential conflicts of interest and to attempt to allocate such investment opportunities in a fair and equitable manner, the investment adviser has implemented allocation policies and procedures. These policies and procedures are intended to give all clients of the investment adviser, including the Trust(s), fair access to investment opportunities consistent with the requirements of organizational documents, investment strategies, applicable laws and regulations, and the fiduciary duties of the investment adviser.

Payments to Broker-Dealers and Other Financial Intermediaries. The investment adviser and/or EVD may pay compensation, out of their own funds and not as an expense of a Fund, to certain financial intermediaries (which may include affiliates of the investment adviser and EVD), including recordkeepers and administrators of various deferred compensation plans, in connection with the sale, distribution, marketing and retention of shares of the Trust and/or shareholder servicing. The prospect of receiving, or the receipt of, additional compensation, as described above, by financial intermediaries may provide such financial intermediaries and their financial advisors and other salespersons with an incentive to favor sales of shares of a Fund over other investment options with respect to which these financial intermediaries do not receive additional compensation (or receives lower levels of additional compensation). These payment arrangements, however, will not change the price that an investor pays for shares of a Fund or the amount that the Trust receives to invest on behalf of an investor. Investors may wish to take such payment arrangements into account when considering and evaluating any recommendations relating to Fund shares and should review carefully any disclosures provided by financial intermediaries as to their compensation. In addition, in certain circumstances, the investment adviser may restrict, limit or reduce the amount of a Fund's investment, or restrict the type of governance or voting rights it acquires or exercises, where the Trust (potentially together with Morgan Stanley) exceeds a certain ownership interest, or possesses certain degrees of voting or control or has other interests.

Morgan Stanley Trading and Principal Investing Activities. Notwithstanding anything to the contrary herein, Morgan Stanley will generally conduct its sales and trading businesses, publish research and analysis, and render investment advice without regard for a Fund's holdings, although these activities could have an adverse impact on the value of one or more of the Trust's investments, or could cause Morgan Stanley to have an interest in one or more portfolio investments that is different from, and potentially adverse to, that of a Fund.

Morgan Stanley's Investment Banking Activities. Morgan Stanley advises clients on a variety of mergers, acquisitions, restructuring, bankruptcy and financing transactions. Morgan Stanley may act as an advisor to clients, including other investment funds that may compete with a Fund and with respect to investments that a Fund may hold. Morgan Stanley may give advice and take action with respect to any of its clients or proprietary accounts that may differ from the advice given, or may involve an action of a different timing or nature than the action taken, by a Fund. Morgan Stanley may give advice and provide recommendations to persons competing with a Fund and/or any of a Fund's investments that are contrary to the Trust's best interests and/or the best interests of any of its investments.

Eaton Vance National Municipal Opportunities Trust 48 Prospectus dated July 22,2021

General Process for Potential Conflicts. All of the transactions described above involve the potential for conflicts of interest between the investment adviser, related persons of the investment adviser and/or their clients. The Investment Advisers Act of 1940, as amended (the 'Advisers Act') the 1940 Act and ERISA impose certain requirements designed to decrease the possibility of conflicts of interest between an investment adviser and its clients. In some cases, transactions may be permitted subject to fulfillment of certain conditions. Certain other transactions may be prohibited. In addition, the investment adviser has instituted policies and procedures designed to prevent conflicts of interest from arising and, when they do arise, to ensure that it effects transactions for clients in a manner that is consistent with its fiduciary duty to its clients and in accordance with applicable law. The investment adviser seeks to ensure that potential or actual conflicts of interest are appropriately resolved taking into consideration the overriding best interests of the client.

Federal Income Tax Matters

The discussions below and certain disclosure in the SAI provide general tax information related to an investment in the Common Shares. Because tax laws are complex and often change, you should consult your tax adviser about the tax consequences of an investment in the Trust. For instance, the Biden administration has proposed a significant number of changes to the U.S. tax laws, including an increase in the maximum tax rate applicable to U.S. corporations and certain individuals, which could potentially have retroactive effect. These changes may significantly alter the after-tax return of the Common Shareholders. The following tax discussion assumes that you are a U.S. Common Shareholder that is not subject to special rules under the Internal Revenue Code of 1986, as amended (the 'Code'), and that you hold the Common Shares as a capital asset within the meaning of Section 1221 of the Code.

A U.S. Common Shareholder means an owner of Common Shares that, for U.S. federal income tax purposes, is a citizen or individual resident of the United States, a corporation (including any entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States or any state thereof or the District of Columbia, an estate the income of which is subject to U.S. federal income taxation regardless of its source, or a trust if (i) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have the authority to control all substantial decisions of the trust or (ii) the trust has a valid election in effect under applicable U.S. Treasury Regulations to be treated as a U.S. person.

The Trust has elected to be treated and intends to qualify each year as a regulated investment company ('RIC') under Subchapter M of the Code. In order to qualify as a RIC, the Trust must satisfy certain requirements regarding the sources of its income, the diversification of its assets and the distribution of its income. As a RIC, the Trust is not expected to be subject to U.S. federal income tax to the extent that it timely distributes its investment company taxable income and net capital gains.

The Trust currently intends to invest a sufficient portion of its assets in tax-exempt municipal obligations so that it will be permitted to pay 'exempt-interest dividends' (as defined under applicable U.S. federal income tax law). Each distribution of exempt-interest dividends, whether paid in cash or reinvested in additional Common Shares, ordinarily will constitute income exempt from regular U.S. federal income tax under current U.S. federal tax law, but it may be subject to state and local taxes. Interest on certain municipal obligations, such as certain private activity bonds, however, is included as an item of tax preference in determining the amount of a taxpayer's alternative minimum taxable income. To the extent that the Trust receives income from such municipal obligations, a portion of the dividends paid by the Trust, although exempt from regular U.S. federal income tax, will be taxable to Common Shareholders to the extent that their tax liability is determined under the AMT. Furthermore, exempt-interest dividends are included in determining what portion, if any, of a person's social security and railroad retirement benefits will be includible in gross income subject to regular U.S. federal income tax. The Trust will annually provide a report indicating the percentage of the Trust's income attributable to municipal obligations subject to the AMT.

In addition to exempt-interest dividends, the Trust also may distribute to its Common Shareholders amounts that are treated as long-term capital gain or ordinary income (which may include short-term capital gains). These distributions may be subject to federal, state and local taxation, depending on a Common Shareholder's situation. Taxable distributions are taxable whether or not such distributions are paid in cash or reinvested in additional Common Shares in the Trust. Net capital gain distributions (the excess of net long-term capital gain over net short-term capital loss, in each case determined with reference to certain loss carryforwards) designated as capital gains dividends are generally taxable at rates applicable to long-term capital gains regardless of how long a Common Shareholder has held his or her Common Shares. The Trust does not currently expect that any part of its distributions to Common Shareholders from its investments will qualify for the dividends-received deduction available to corporate Common Shareholders or as 'qualified dividend income' to noncorporate Common Shareholders.

As a RIC, the Trust will not be subject to U.S. federal income tax in any taxable year provided that it meets certain distribution requirements. If the Trust retains any net capital gain or investment company taxable income, it will be subject to tax at regular corporate rates on the amount retained. If the Trust retains any net capital gain, it may designate the

Eaton Vance National Municipal Opportunities Trust 49 Prospectus dated July 22,2021

retained amount as undistributed capital gains in a notice to its Common Shareholders who (i) will be required to include in income for U.S. federal income tax purposes, as long-term capital gain, their share of such undistributed amount; (ii) will be entitled to credit their proportionate share of the tax paid by the Trust on such undistributed amount against their U.S. federal income tax liabilities, if any; and (iii) will be entitled to claim refunds to the extent the credit exceeds such liabilities. For U.S. federal income tax purposes, the tax basis of Common Shares owned by a Common Shareholder of the Trust will be increased by an amount equal to the difference between the amount of undistributed capital gains included in the Common Shareholder's gross income under clause (i) and the tax deemed paid by the Common Shareholder under clauses (ii) and (iii) of the preceding sentence. The Trust is not required to, and there can be no assurance that the Trust will, make this designation if it retains all or a portion of its net capital gain in a taxable year.

The Internal Revenue Service ('IRS') currently requires that a RIC that has two or more classes of stock allocate to each such class proportionate amounts of each type of its income (such as exempt-interest, ordinary income and capital gains) based on the percentage of total dividends distributed to each class for the tax year. Accordingly, if the Trust issues preferred Common Shares, it will designate dividends made with respect to Common Shares and preferred Common Shares as consisting of particular types of income (e.g., exempt-interest, net capital gain and ordinary income) in accordance with the proportionate share of each class in the total dividends paid by the Trust during the year.

Investors who purchase Common Shares at a time when the Trust's net asset value reflects gains that are either unrealized or realized but undistributed will pay the full price for the Common Shares and then may receive some portion of the purchase price back as a taxable distribution. Dividends and other taxable distributions declared by the Trust in October, November or December to Common Shareholders of record on a specified date in such month and paid during the following January are deemed to have been paid by the Trust on December 31 of the preceding year.

Each Common Shareholder will receive an annual statement summarizing the source and tax status of all distributions (including net capital gains credited to the Common Shareholder but retained by the Trust) after the close of the Trust's taxable year.

The redemption, sale or exchange of Common Shares normally will result in capital gain or loss to Common Shareholders. Generally a Common Shareholder's gain or loss will be long-term capital gain or loss if the Common Shares have been held for more than one year, and short-term capital gain or loss if the Common Shares are held for one year or less. Any loss on the sale of Common Shares that have been held for six months or less will be disallowed to the extent of any distribution of exempt-interest dividends received with respect to such Common Shares, unless the Common Shares are of a RIC that declares exempt-interest dividends on a daily basis in an amount equal to at least 90% of its net tax-exempt interest and distributes such dividends on a monthly or more frequent basis. If a Common Shareholder sells or otherwise disposes of Common Shares before holding them for more than six months, any loss on the sale or disposition will be treated as a long-term capital loss to the extent of any capital gain dividends received by the Common Shareholder on such Common Shares. Any loss realized on a sale or exchange of Common Shares of the Trust will be disallowed to the extent those Common Shares of the Trust are replaced by other substantially identical Common Shares of the Trust or other substantially identical stock or securities (including through reinvestment of dividends) within a period of 61 days beginning 30 days before and ending 30 days after the date of disposition of the original Common Shares. In that event, the basis of the replacement Common Shares of the Trust will be adjusted to reflect the disallowed loss.

Any interest on indebtedness incurred or continued to purchase or carry the Trust's Common Shares on which exempt-interest dividends are paid is not deductible in proportion to the percentage that the Trust's distribution of exempt-interest dividends bears to all of the Trust's distributions, excluding capital gain dividends. Under certain applicable rules, the purchase or ownership of Common Shares may be considered to have been made with borrowed funds even though such funds are not directly used for the purchase or ownership of the Common Shares. In addition, if you receive Social Security or certain railroad retirement benefits, you may be subject to U.S. federal income tax on a portion of such benefits as a result of receiving investment income, including exempt-interest dividends and other distributions paid by the Trust.

If the Trust invests in certain pay-in-kind securities, zero coupon securities, deferred interest securities or, in general, any other securities with original issue discount (or with market discount if the Trust elects to include market discount in income currently), the Trust must accrue income on such investments for each taxable year, which generally will be prior to the receipt of the corresponding cash payments. However, the Trust must distribute to Common Shareholders, at least annually, all or substantially all of its investment company taxable income (determined without regard to the deduction for dividends paid) and net tax-exempt income, including such accrued income, to qualify as a RIC and to avoid U.S. federal income and excise taxes. Therefore, the Trust may have to dispose of its portfolio investments under disadvantageous circumstances to generate cash, or may have to leverage itself by borrowing the cash, to satisfy these distribution requirements.

Eaton Vance National Municipal Opportunities Trust 50 Prospectus dated July 22,2021

The net investment income of certain U.S. individuals, estates and trusts is subject to a 3.8% Medicare contribution tax. For individuals, the tax is on the lesser of the 'net investment income' and the excess of modified adjusted gross income over $200,000 (or $250,000 if married filing jointly). Net investment income includes, among other things, interest, dividends (other than exempt-interest dividends), and gross income and capital gains derived from passive activities and trading in securities or commodities. Net investment income is reduced by deductions 'properly allocable' to this income.

The Trust may be required to withhold, for U.S. federal income tax purposes, a certain portion of all taxable distributions payable to Common Shareholders who fail to provide the Trust with their correct taxpayer identification number or make required certifications, or if the Common Shareholders have been notified by the IRS that they are subject to backup withholding. Backup withholding is not an additional tax. Any amounts withheld may be credited against a Common Shareholder's U.S. federal income tax liability.

Certain foreign entities including foreign entities acting as intermediaries may be subject to a 30% withholding tax on ordinary dividend income paid under the Foreign Account Tax Compliance Act ('FATCA'). To avoid withholding, foreign financial institutions subject to FATCA must agree to disclose to the relevant revenue authorities certain information regarding their direct and indirect U.S. owners and other foreign entities must certify certain information regarding their direct and indirect U.S. owners to the Trust. In addition, the IRS and the Department of Treasury have issued proposed regulations providing that these withholding rules will not be applicable to the gross proceeds of share redemptions or capital gain dividends the Trust pays. For more detailed information regarding FATCA withholding and compliance, please refer to the SAI.

The Trust may invest in other securities the U.S. federal income tax treatment of which is uncertain or subject to recharacterization by the IRS. To the extent the tax treatment of such securities or their income differs from the tax treatment expected by the Trust, it could affect the timing or character of income recognized by the Trust, requiring the Trust to purchase or sell securities, or otherwise change its portfolio, in order to comply with the tax rules applicable to RICs under the Code.

Dividend Reinvestment Plan

Pursuant to the Trust's dividend reinvestment plan (the 'Plan'), unless a Common Shareholder elects to receive distributions in cash, all distributions will be automatically reinvested in additional Common Shares.

American Stock Transfer & Trust Company LLC (the 'Plan Agent') serves as agent for the Common Shareholders in administering the Plan. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or if the Common Shares are held in street or other nominee name, then to the nominee) by the Plan Agent, as disbursing agent. Participation in the Plan is completely voluntary and may be terminated or resumed at any time without penalty by written notice if received by the Plan Agent prior to any distribution record date.

Common Shares will be acquired by the Plan Agent or an independent broker-dealer for the participants' accounts, depending upon the circumstances described below, either (i) through receipt of additional previously authorized but unissued Common Shares from the Trust ('newly issued Common Shares') or (ii) by purchase of outstanding Common Shares on the open market ('open-market purchases') on the NYSE or elsewhere. If on the payment date for the distribution, the NAV per Common Share is equal to or less than the market price per Common Share plus estimated brokerage commissions (such condition being referred to herein as 'market premium'), the Plan Agent will invest the distribution amount in newly issued Common Shares on behalf of the participants. The number of newly issued Common Shares to be credited to each participant's account will be determined by dividing the dollar amount of the distribution by the NAV per Common Share on the date the Common Shares are issued, provided that the maximum discount from the then current market price per Common Share on the date of issuance may not exceed 5%. If on the distribution payment date the NAV per Common Share is greater than the market value plus estimated brokerage commissions (such condition being referred to herein as 'market discount'), the Plan Agent will invest the distribution amount in Common Shares acquired on behalf of the participants in open-market purchases.

In the event of a market discount on the distribution payment date, the Plan Agent will have up to 30 days after the distribution payment date to invest the distribution amount in Common Shares acquired in open-market purchases. If, before the Plan Agent has completed its open-market purchases, the market price of a Common Share exceeds the NAV per Common Share, the average per Common Share purchase price paid by the Plan Agent may exceed the NAV of the Common Shares, resulting in the acquisition of fewer Common Shares than if the distribution had been paid in newly issued Common Shares on the distribution payment date. Therefore, the Plan provides that if the Plan Agent is unable to invest the full distribution amount in open-market purchases during the purchase period or if the market discount shifts to a market premium during the purchase period, the Plan Agent will cease making open-market purchases and will invest the uninvested portion of the distribution amount in newly issued Common Shares.

Eaton Vance National Municipal Opportunities Trust 51 Prospectus dated July 22,2021

The Plan Agent maintains all Common Shareholders' accounts in the Plan and furnishes written confirmation of all transactions in the accounts, including information needed by Common Shareholders for tax records. Common Shares in the account of each Plan participant will be held by the Plan Agent on behalf of the Plan participant, and each Common Shareholder proxy will include those Common Shares purchased or received pursuant to the Plan. The Plan Agent will forward all proxy solicitation materials to participants and vote proxies for Common Shares held pursuant to the Plan in accordance with the instructions of the participants. In the case of Common Shareholders such as banks, brokers or nominees that hold Common Shares for others who are the beneficial owners, the Plan Agent will administer the Plan on the basis of the number of Common Shares certified from time to time by the record Common Shareholder's name and held for the account of beneficial owners who participate in the Plan.

There will be no brokerage charges to Common Shares issued directly by the Trust as a result of distributions payable either in Common Shares or in cash. However, each Plan participant will pay a pro rata share of brokerage commissions incurred with respect to the Plan Agent's open-market purchases in connection with the reinvestment of distributions.

Common Shareholders participating in the Plan may receive benefits not available to Common Shareholders not participating in the Plan. If the market price (plus commissions) of the Common Shares is above their NAV, participants in the Plan will receive Common Shares of the Trust purchased at a discount to market price and having a current value that exceeds the cash distributions they would have otherwise received on their Common Shares. If the market price (plus commissions) of the Common Shares is below their NAV, Plan participants will receive Common Shares with a NAV that exceeds the cash distributions they would have otherwise received on their Common Shares. There may, however, be insufficient Common Shares available in the market at prices below NAV to satisfy the Plan's requirements, in which case the Plan Agent will acquire newly issued Common Shares. Also, since the Trust does not redeem its Common Shares, the price on resale may be more or less than their NAV.

Experience under the Plan may indicate that changes are desirable. Accordingly, upon 30 days' notice to Plan participants, the Trust reserves the right to amend or terminate the Plan. A Plan participant will be charged a $5.00 service charge and pay brokerage charges whenever he or she directs the Plan Agent to sell Common Shares held in a distribution reinvestment account.

The Plan Agent will reinvest all shares, including fractions, under the Plan. Upon any termination in the Plan for a participant, the Plan Agent will issue a cash adjustment at the market value of shares at the time of termination for any fractional share held.

Any inquiries regarding the Plan can be directed to the Plan Agent, AST, at 1-866-439-6787.

Description of Capital Structure

The Trust is an unincorporated business trust established under the laws of The Commonwealth of Massachusetts by an Agreement and Declaration of Trust (the 'Declaration of Trust'). The Declaration of Trust provides that the Trustees of the Trust may authorize separate classes of shares of beneficial interest. The Trustees have authorized an unlimited number of Common Shares. The Trust holds annual meetings of shareholders in compliance with the requirements of the NYSE.

COMMON SHARES

The Declaration of Trust permits the Trust to issue an unlimited number of full and fractional Common Shares. Each Common Share represents an equal proportionate interest in the assets of the Trust with each other Common Share in the Trust. Common Shareholders are entitled to the payment of distributions when, as, and if declared by the Board. The 1940 Act or the terms of any future borrowings or issuance of preferred shares may limit the payment of distributions to the Common Shareholders. Each whole Common Share shall be entitled to one vote as to matters on which it is entitled to vote pursuant to the terms of the Declaration of Trust on file with the SEC.

The Trust's By-Laws include provisions (the 'Control Share Provisions'), pursuant to which a shareholder who obtains beneficial ownership of Fund shares in a 'Control Share Acquisition' may exercise voting rights with respect to such shares only to the extent the authorization of such voting rights is approved by other shareholders of the Trust. The By-Laws define a 'Control Share Acquisition,' pursuant to various conditions and exceptions, to include an acquisition of Fund shares that would give the beneficial owner, upon the acquisition of such shares, the ability to exercise voting power, but for the Control Share Provisions, in the election of Fund Trustees in any of the following ranges: (i) one-tenth or more, but less than one-fifth of all voting power; (ii) one-fifth or more, but less than one-third of all voting power; (iii) one-third or more, but less than a majority of all voting power; or (iv) a majority or more of all voting power. Subject to various conditions and procedural requirements, including the delivery of a 'Control Share Acquisition Statement' to the Trust's secretary setting forth certain required information, a shareholder who obtains beneficial ownership of shares in a Control Share Acquisition generally may request a vote of Fund shareholders (excluding such acquiring shareholder and certain other interested shareholders) to approve the authorization of voting rights for such shares at the next annual meeting of Fund shareholders following the Control Share Acquisition. See 'Certain Provisions of the Organizational Documents' below for more information.

Eaton Vance National Municipal Opportunities Trust 52 Prospectus dated July 22,2021

The By-Laws establish qualification criteria applicable to prospective Trustees and generally require that advance notice be given to the Trust in the event a shareholder desires to nominate a person for election to the Board or to transact any other business at a meeting of shareholders. Any notice by a shareholder must be accompanied by certain information as required by the By-Laws. No shareholder proposal will be considered at any meeting of shareholders of the Trust if such proposal is submitted by a shareholder who does not satisfy all applicable requirements set forth in the By-Laws.

In the event of the liquidation of the Trust, after paying or adequately providing for the payment of all liabilities of the Trust and the liquidation preference with respect to any outstanding preferred shares, and upon receipt of such releases, indemnities and refunding agreements as they deem necessary for their protection, the Board may distribute the remaining assets of the Trust among the Common Shareholders. The Declaration of Trust provides that Common Shareholders are not liable for any liabilities of the Trust and permits inclusion of a clause to that effect in every agreement entered into by the Trust and, in coordination with the Trust's By-Laws, indemnifies shareholders against any such liability. Although shareholders of an unincorporated business trust established under Massachusetts law may, in certain limited circumstances, be held personally liable for the obligations of the business trust as though they were general partners, the provisions of the Trust's Organizational Documents described in the foregoing sentence make the likelihood of such personal liability remote.

The Trust has no current intention to issue preferred shares or to borrow money. However, if at some future time there are any borrowings or preferred shares outstanding, the Trust may not be permitted to declare any cash distribution on its Common Shares, unless at the time of such declaration, (i) all accrued distributions on preferred shares or accrued interest on borrowings have been paid and (ii) the value of the Trust's total assets (determined after deducting the amount of such distribution), less all liabilities and indebtedness of the Trust not represented by senior securities, is at least 300% of the aggregate amount of such securities representing indebtedness and at least 200% of the aggregate amount of securities representing indebtedness plus the aggregate liquidation value of the outstanding preferred shares. In addition to the requirements of the 1940 Act, the Trust may be required to comply with other asset coverage requirements as a condition of the Trust obtaining a rating of preferred shares from a nationally recognized statistical rating agency (a 'Rating Agency'). These requirements may include an asset coverage test more stringent than under the 1940 Act. This limitation on the Trust's ability to make distributions on its Common Shares could in certain circumstances impair the ability of the Trust to maintain its qualification for taxation as a regulated investment company for federal income tax purposes. If the Trust were in the future to issue preferred shares or borrow money, it would intend, however, to the extent possible to purchase or redeem preferred shares or reduce borrowings from time to time to maintain compliance with such asset coverage requirements and may pay special distributions to the holders of the preferred shares in certain circumstances in connection with any potential impairment of the Trust's status as a regulated investment company. See 'Federal Income Tax Matters.' Depending on the timing of any such redemption or repayment, the Trust may be required to pay a premium in addition to the liquidation preference of the preferred shares to the holders thereof.

The Trust has no present intention of offering additional Common Shares, except as described herein. Other offerings of its Common Shares, if made, will require approval of the Board. Any additional offering will not be sold at a price per Common Share below the then current net asset value (exclusive of underwriting discounts and commissions) except in connection with an offering to existing Common Shareholders or with the consent of a majority of the outstanding Common Shares. The Common Shares have no preemptive rights.

The Trust generally will not issue Common Share certificates. However, upon written request to the Trust's transfer agent, a share certificate will be issued for any or all of the full Common Shares credited to an investor's account. Common Share certificates that have been issued to an investor may be returned at any time.

REPURCHASE OF COMMON SHARES AND OTHER DISCOUNT MEASURES

Because shares of closed-end management investment companies frequently trade at a discount to their NAVs, the Board has determined that from time to time it may be in the interest of shareholders for the Trust to take corrective actions. The Board, in consultation with Eaton Vance, will review at least annually the possibility of open market repurchases and/or tender offers for the Common Shares and will consider such factors as the market price of the Common Shares, the NAV of the Common Shares, the liquidity of the assets of the Trust, effect on the Trust's expenses, whether such transactions would impair the Trust's status as a regulated investment company or result in a failure to comply with applicable asset coverage requirements, general economic conditions and such other events or conditions which may have a material effect on the Trust's ability to consummate such transactions. There are no assurances that the Board will, in fact, decide to undertake either of these actions or if undertaken, that such actions will result in the Trust's Common Shares trading at a price which is equal to or approximates their NAV. In recognition of the possibility that the Common Shares might trade at a discount to NAV and that any such discount may not be in the interest of shareholders, the Board, in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount.

Eaton Vance National Municipal Opportunities Trust 53 Prospectus dated July 22,2021

In November 2013, the Board of Trustees initially approved a share repurchase program for the Trust. Pursuant to the reauthorization of the share repurchase program by the Board of Trustees in December 2019, the Trust is authorized to repurchase up to 10% of its common shares outstanding as of the last day of the prior calendar year at market prices when shares are trading at a discount to net asset value. The share repurchase program does not obligate the Trust to purchase a specific amount of shares. Results of the share repurchase program are disclosed in the Trust's annual and semiannual reports to shareholders.

PREFERRED SHARES

The Trust has no current intention of issuing any shares other than the Common Shares. However, the Declaration of Trust authorizes the issuance of an unlimited number of shares of beneficial interest with preference rights (the 'preferred shares') in one or more series, with rights as determined by the Board, by action of the Board without the approval of the Common Shareholders.

Under the requirements of the 1940 Act, the Trust must, immediately after the issuance of any preferred shares, have an 'asset coverage' of at least 200%. Asset coverage means the ratio which the value of the total assets of the Trust, less all liabilities and indebtedness not represented by senior securities (as defined in the 1940 Act), bears to the aggregate amount of senior securities representing indebtedness of the Trust, if any, plus the aggregate liquidation preference of the preferred shares. If the Trust seeks a rating for preferred shares, asset coverage requirements in addition to those set forth in the 1940 Act may be imposed. The liquidation value of any preferred shares would be expected to equal their aggregate original purchase price plus redemption premium, if any, together with any accrued and unpaid distributions thereon (on a cumulative basis), whether or not earned or declared. The terms of any preferred shares, including their distribution rate, voting rights, liquidation preference and redemption provisions, will be determined by the Board (subject to applicable law and the Trust's Declaration of Trust) if and when it authorizes preferred shares. The Trust may issue preferred shares that provide for the periodic redetermination of the distribution rate at relatively short intervals through an auction or remarketing procedure, although the terms of such preferred shares may also enable the Trust to lengthen such intervals. At times, the distribution rate on any preferred shares may exceed the Trust's return after expenses on the investment of proceeds from the preferred shares and the Trust's leverage structure, resulting in a lower rate of return to Common Shareholders than if the Trust were not so structured.

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Trust, the terms of any preferred shares may entitle the holders of preferred shares to receive a preferential liquidating distribution (expected to equal the original purchase price per share plus redemption premium, if any, together with accrued and unpaid dividends, whether or not earned or declared and on a cumulative basis) before any distribution of assets is made to Common Shareholders. After payment of the full amount of the liquidating distribution to which they are entitled, the preferred shareholders would not be entitled to any further participation in any distribution of assets by the Trust.

Holders of preferred shares, voting as a class, would be entitled to elect two of the Trust's Trustees if any preferred shares are issued. The holders of both the Common Shares and the preferred shares (voting together as a single class with each share entitling its holder to one vote) would be entitled to elect the remaining Trustees of the Trust. Under the 1940 Act, if at any time dividends on the preferred shares are unpaid in an amount equal to two full years' dividends thereon, the holders of all outstanding preferred shares, voting as a class, will be allowed to elect a majority of the Board until all distributions in arrears have been paid or declared and set apart for payment. In addition, if required by a Rating Agency rating the preferred shares or if the Board determines it to be in the best interests of the Common Shareholders, issuance of the preferred shares may result in more restrictive provisions than required under the 1940 Act. In this regard, holders of preferred shares may be entitled to elect a majority of the Board in other circumstances, for example, if one payment on the preferred shares is in arrears. The differing rights of the holders of preferred and Common Shares with respect to the election of Trustees do not affect the obligation of all Trustees to take actions they believe to be consistent with the best interests of the Trust. All such actions must be consistent with (i) the obligations of the Trust with respect to the holders of preferred shares (which obligations arise primarily from the contractual terms of the preferred shares, as specified in the Declaration of Trust and By-laws of the Trust) and (ii) the fiduciary duties owed to the Trust, which include the duties of loyalty and care.

In the event of any future issuance of preferred shares, the Trust likely would seek a credit rating for such preferred shares from a Rating Agency. In such event, as long as preferred shares are outstanding, the composition of its portfolio will reflect guidelines established by such Rating Agency. Based on previous guidelines established by Rating Agencies for the securities of other issuers, the Trust anticipates that the guidelines with respect to any preferred shares would

Eaton Vance National Municipal Opportunities Trust 54 Prospectus dated July 22,2021

establish a set of tests for portfolio composition and asset coverage that supplement (and in some cases are more restrictive than) the applicable requirements under the 1940 Act. Although no assurance can be given as to the nature or extent of the guidelines that may be imposed in connection with obtaining a rating of any preferred shares, the Trust anticipates that such guidelines would include asset coverage requirements that are more restrictive than those under the 1940 Act, restrictions on certain portfolio investments and investment practices and certain mandatory redemption requirements relating to any preferred shares. No assurance can be given that the guidelines actually imposed with respect to any preferred shares by a Rating Agency would be more or less restrictive than those described in this Prospectus.

EFFECTS OF LEVERAGE

As discussed above, the Trust currently uses leverage in the form of residual interest bonds. The Trust will not utilize leverage in excess of 15% of its gross assets. Although the Trust has no current intention to do so, the Trust is authorized also to utilize leverage through the issuance of preferred shares and/or borrowings, including the issuance of debt securities. The Trust may borrow for temporary, emergency or other purposes as permitted by the 1940 Act. In the event that the Trust determines in the future to utilize alternative or additional forms of leverage, there can be no assurance that such strategy would be successful during any period in which it is employed. Leverage creates risks for Common Shareholders, including the likelihood of greater volatility of NAV and market price of the Common Shares and the risk that fluctuations in leverage costs may affect the income and return to Common Shareholders. To the extent the amounts available for distribution derived from securities purchased with proceeds received from leverage exceed the cost of leverage, the Trust's distributions would be greater than if leverage had not been used. Conversely, if the amounts available for distribution derived from securities purchased with such proceeds are not sufficient to cover the cost of leverage, distributions to Common Shareholders would be less than if leverage had not been used. In the latter case, Eaton Vance, in its best judgment, may nevertheless determine to maintain the Trust's leveraged position if it deems such action to be appropriate. The costs of an offering of preferred shares and/or a borrowing program would be borne by Common Shareholders and consequently would result in a reduction of the NAV of Common Shares.

In addition, the advisory fee paid to Eaton Vance is calculated on the basis of the Trust's average daily gross assets. 'Gross assets' of the Trust means total assets of the Trust, including assets attributable to any form of leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles. This means that the advisory fees paid by the Trust would be higher if leverage is utilized. In this regard, holders of preferred shares would not bear the investment advisory fee. Rather, Common Shareholders would bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds of the preferred shares offering.

CERTAIN PROVISIONS OF THE DECLARATION OF TRUST

Summary of Anti-Takeover Provisions in the Organizational Documents

Pursuant to the Organizational Documents, the Board is divided into three classes, with the term of one class expiring at each annual meeting of holders of Common Shares and preferred shares. At each annual meeting, one class of Trustees is elected to a three-year term. This provision could delay the replacement of a majority of the Board, thereby increasing stability of the composition of the Board. In addition, in the event a Trustee is not elected at an annual meeting at which such Trustee's term expires, and a nominee presented to shareholders as such Trustee's successor is also not elected, then the incumbent Trustee shall remain a member of the relevant class of Trustees and hold office until the expiration of the term applicable to Trustees in that class. In a contested Trustee election, a nominee must receive the affirmative vote of a majority of the shares outstanding and entitled to vote in order to be elected. A Trustee may be removed from office only (i) for cause by a written instrument signed by the remaining Trustees or (ii) by a vote of the holders of at least two-thirds of the class of shares of the Trust that elected such Trustee and are entitled to vote on the matter. These provisions similarly could delay the replacement of Trustees, which similarly increases stability of the composition of the Board.

The Organizational Documents establish supermajority voting requirements with respect to certain other matters. The Declaration of Trust requires the favorable vote of the holders of at least 75% of the outstanding shares of each class of the Trust, voting as a class, then entitled to vote to approve, adopt or authorize certain transactions with 5%-or-greater holders ('Principal Shareholders') of a class of shares and their associates, unless the Board shall by resolution have approved a memorandum of understanding with such holders, in which case normal voting requirements would be in effect. For purposes of these provisions, a Principal Shareholder refers to any person who, whether directly or indirectly and whether alone or together with its affiliates and associates, beneficially owns 5% or more of the outstanding shares of any class of beneficial interest of the Trust. The transactions subject to these special approval requirements are: (i) the

Eaton Vance National Municipal Opportunities Trust 55 Prospectus dated July 22,2021

merger or consolidation of the Trust or any subsidiary of the Trust with or into any Principal Shareholder; (ii) the issuance of any securities of the Trust to any Principal Shareholder for cash; (iii) the sale, lease or exchange of all or any substantial part of the assets of the Trust to any Principal Shareholder (except assets determined by the Board to have an aggregate fair market value of less than $1,000,000, aggregating for the purpose of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period); or (iv) the sale, lease or exchange to or with the Trust or any subsidiary thereof, in exchange for securities of the Trust, of any assets of any Principal Shareholder (except assets determined by the Board to have an aggregate fair market value of less than $1,000,000, aggregating for the purposes of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period). For information on the Control Share Provisions and the qualification criteria applicable to prospective Trustees in the Trust's By-Laws, see 'Description of Capital Structure - Common Shares.'

The Board believes that these provisions are in the best interests of the Trust and its shareholders. These provisions may provide some protection to the Trust against insurgent campaigns from 'activist' investors that may, under some circumstances, impede the Trust's ability to achieve its investment objective and may otherwise threaten to harm the long-term interests of the Trust and its other shareholders. These provisions promote continuity and stability and enhance the Trust's ability to pursue the Trust's investment strategies that are consistent with its stated investment objective and investment policies. Because these provisions may discourage third parties from seeking to obtain control of the Trust or from seeking to effect a tender offer or similar transaction, they may reduce opportunities for Common Shareholders to sell their Common Shares at a short-term premium over the then-current market price. However, they allow the Board to balance the interests of the entire shareholder base in evaluating these and other types of transactions rather than prioritizing the interests of certain shareholders.

The voting thresholds described above and below under 'Conversion to Open-End Fund' are higher than those (if any) established under Massachusetts or federal law. The Board has determined that these voting requirements are in the best interest of holders of Common Shares and preferred shares generally. Reference is made to the Organizational Documents on file with the SEC for the full text of these provisions.

Conversion to Open-End Fund

The Trust may be converted to an open-end investment company at any time if approved by the lesser of (i) two-thirds or more of the Trust's then outstanding Common Shares and preferred shares, each voting separately as a class, or (ii) more than 50% of the then outstanding Common Shares and preferred shares, voting separately as a class if such conversion is recommended by at least 75% of the Trustees then in office. If approved in the foregoing manner, conversion of the Trust could not occur until 90 days after the Common Shareholders' meeting at which such conversion was approved and would also require at least 30 days' prior notice to all Common Shareholders. Conversion of the Trust to an open-end management investment company also would require the redemption of any outstanding preferred shares could require the repayment of borrowings. The Board believes that the closed-end structure is desirable, given the Trust's investment objectives and policies. Investors should assume, therefore, that it is unlikely that the Board would vote to convert the Trust to an open-end management investment company.

Eaton Vance National Municipal Opportunities Trust 56 Prospectus dated July 22,2021

Custodian and Transfer Agent

State Street Bank and Trust Company ('State Street'), State Street Financial Center, One Lincoln Street, Boston, MA 02111, is the custodian of the Trust and will maintain custody of the securities and cash of the Trust. State Street maintains the Trust's general ledger and computes NAV per share at least weekly. State Street also attends to details in connection with the sale, exchange, substitution, transfer and other dealings with the Trust's investments, and receives and disburses all funds. State Street also assists in preparation of shareholder reports and the electronic filing of such reports with the SEC.

American Stock Transfer & Trust Company, LLC, 6201 15th Avenue, Brooklyn, NY 11219 is the transfer agent and dividend disbursing agent of the Trust.

Legal Matters

Certain legal matters in connection with the Common Shares will be passed upon for the Trust by internal counsel for Eaton Vance.

Reports to Shareholders

The Trust will send to Common Shareholders unaudited semi-annual and audited annual reports, including a list of investments held.

Independent Registered Public Accounting Firm

Deloitte & Touche LLP ('Deloitte'), 200 Berkeley Street, Boston, MA 02116, independent registered public accounting firm, audits the Trust's financial statements. Deloitte and/or its affiliates provide other audit, tax and related services to the Trust.

Additional Information

The Prospectus and the SAI do not contain all of the information set forth in the Registration Statement that the Trust has filed with the SEC. The complete Registration Statement may be obtained from the SEC upon payment of the fee prescribed by its rules and regulations. The SAI can be obtained without charge by calling 1-800-262-1122.

Statements contained in this Prospectus as to the contents of any contract or other document referred to are not necessarily complete, and, in each instance, reference is made to the copy of such contract or other document filed as an exhibit to the Registration Statement of which this Prospectus forms a part, each such statement being qualified in all respects by such reference.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Trust's annual and semi-annual shareholder reports are no longer being sent by mail unless you specifically request paper copies of the reports. Instead, the reports are available on the Trust's website (funds.eatonvance.com/closed-end-fund-and-term-trust-documents.php), and you will be notified by mail each time a report is posted and provided with a website address to access the report. If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. If you hold shares at the Trust's transfer agent, American Stock Transfer & Trust Company, LLC ('AST'), you may elect to receive shareholder reports and other communications from the Trust electronically by contacting AST. If you own your shares through a financial intermediary (such as a broker-dealer or bank), you must contact your financial intermediary to sign up. You may elect to receive all future Fund shareholder reports in paper free of charge. If you hold shares at AST, you can inform AST that you wish to continue receiving paper copies of your shareholder reports by calling 1-866-439-6787. If you own these shares through a financial intermediary, you must contact your financial intermediary or follow instructions included with this disclosure, if applicable, to elect to continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held with AST or to all funds held through your financial intermediary, as applicable.

Eaton Vance National Municipal Opportunities Trust 57 Prospectus dated July 22,2021

Table of Contents for the Statement of Additional Information

Page
Additional Investment Information and Restrictions 2
Trustees and Officers 13
Investment Advisory and Other Services 22
Determination of Net Asset Value 24
Portfolio Trading 25
Taxes 28
Other Information 33
Custodian 34
Independent Registered Public Accounting Firm 34
Potential Conflicts of Interest 34
Financial Statements 40
APPENDIX A: Ratings 41
APPENDIX B: Eaton Vance Funds Proxy Voting Policy and Procedures 53
APPENDIX C: Adviser Proxy Voting Policies and Procedures 55
Eaton Vance National Municipal Opportunities Trust 58 Prospectus dated July 22,2021

The Trust's Privacy Policy

The Eaton Vance organization is committed to ensuring your financial privacy. Each entity listed below has adopted privacy policy and procedures ('Privacy Program') Eaton Vance believes is reasonably designed to protect your personal information and to govern when and with whom Eaton Vance may share your personal information.

· At the time of opening an account, Eaton Vance generally requires you to provide us with certain information such as name, address, social security number, tax status, account numbers, and account balances. This information is necessary for us to both open an account for you and to allow us to satisfy legal requirements such as applicable anti-money laundering reviews and know-your-customer requirements.
· On an ongoing basis, in the normal course of servicing your account, Eaton Vance may share your information with unaffiliated third parties that perform various services for Eaton Vance and/or your account. These third parties include transfer agents, custodians, broker/dealers and our professional advisers, including auditors, accountants, and legal counsel. Eaton Vance may share your personal information with our affiliates. Eaton Vance may also share your information as required or permitted by applicable law.
· We have adopted a Privacy Program we believe is reasonably designed to protect the confidentiality of your personal information and to prevent unauthorized access to that information.
· We reserve the right to change our Privacy Program at any time upon proper notification to you. You may want to review our Privacy Program periodically for changes by accessing the link on our homepage: www.eatonvance.com.

Our pledge of protecting your personal information applies to the following entities within the Eaton Vance organization: the Eaton Vance Family of Funds, Eaton Vance Management, Eaton Vance WaterOak Advisors, Eaton Vance Distributors, Inc., Eaton Vance Trust Company, Eaton Vance Management (International) Limited, Eaton Vance Advisers International Ltd., Eaton Vance Global Advisors Limited, Eaton Vance Management's Real Estate Investment Group, Boston Management and Research, Calvert Research and Management, and Calvert Funds.

This Privacy Notice supersedes all previously issued privacy disclosures.

For more information about Eaton Vance's Privacy Program or about how your personal information may be used, please call 1-800-262-1122.

Eaton Vance National Municipal Opportunities Trust 59 Prospectus dated July 22,2021

Up to 2,285,745 Shares

Eaton Vance National Municipal Opportunities Trust

Common Shares

Prospectus July 22, 2021

Printed on recycled paper.

Eaton Vance National Municipal Opportunities Trust 60 Prospectus dated July 22,2021

STATEMENT OF
ADDITIONAL INFORMATION

July 22, 2021

Eaton Vance National Municipal Opportunities Trust

Two International Place
Boston, Massachusetts 02110
1-800-262-1122

Table of Contents

Page
Additional Investment Information and Restrictions 2
Trustees and Officers 13
Investment Advisory and Other Services 22
Determination of Net Asset Value 24
Portfolio Trading 25
Taxes 28
Other Information 33
Custodian 34
Independent Registered Public Accounting Firm 34
Potential Conflicts of Interest 34
Financial Statements 40
APPENDIX A: Ratings 41
APPENDIX B: Eaton Vance Funds Proxy Voting Policy and Procedures 53
APPENDIX C: Adviser Proxy Voting Policies and Procedures 55

THIS STATEMENT OF ADDITIONAL INFORMATION ('SAI') IS NOT A PROSPECTUS AND IS AUTHORIZED FOR DISTRIBUTION TO PROSPECTIVE INVESTORS ONLY IF PRECEDED OR ACCOMPANIED BY THE PROSPECTUS OF EATON VANCE NATIONAL MUNICIPAL OPPORTUNITIES TRUST (THE 'TRUST') DATED JULY 22, 2021, AS SUPPLEMENTED FROM TIME TO TIME, WHICH IS INCORPORATED HEREIN BY REFERENCE. THIS SAI SHOULD BE READ IN CONJUNCTION WITH SUCH PROSPECTUS, A COPY OF WHICH MAY BE OBTAINED WITHOUT CHARGE BY CONTACTING YOUR FINANCIAL INTERMEDIARY OR CALLING THE TRUST AT 1-800-262-1122.

Capitalized terms used in this SAI and not otherwise defined have the meanings given them in the Trust's Prospectus and any related Prospectus Supplements.

ADDITIONAL INVESTMENT INFORMATION AND RESTRICTIONS

Primary investment strategies are described in the Prospectus. The following is a description of the various investment practices that may be engaged in, whether as a primary or secondary strategy, and a summary of certain attendant risks. The Adviser may not buy any of the following instruments or use any of the following techniques unless it believes that doing so will help to achieve the Trust's investment objectives.

OTHER INVESTMENTS

Municipal Obligations. Municipal obligations include debt obligations issued to obtain funds for various public purposes, including the construction of a wide range of public facilities, refunding of outstanding obligations and obtaining funds for general operating expenses and loans to other public institutions and facilities. Certain types of bonds are issued by or on behalf of public authorities to finance various privately owned or operated facilities, including certain facilities for the local furnishing of electric energy or gas, sewage facilities, solid waste disposal facilities and other specialized facilities. Municipal obligations include bonds as well as tax-exempt commercial paper, project notes and municipal notes such as tax, revenue and bond anticipation notes of short maturity, generally less than three years. While most municipal bonds pay a fixed rate of interest semiannually in cash, there are exceptions. Some bonds pay no periodic cash interest, but rather make a single payment at maturity representing both principal and interest. Some bonds may pay interest at a variable or floating rate. Bonds may be issued or subsequently offered with interest coupons materially greater or less than those then prevailing, with price adjustments reflecting such deviation. Municipal obligations also include trust certificates representing interests in municipal securities held by a trustee. The trust certificates may evidence ownership of future interest payments, principal payments or both on the underlying securities.

In general, there are three categories of municipal obligations, the interest on which is exempt from federal income tax and is not a tax preference item for purposes of the alternative minimum tax ('AMT'): (i) certain 'public purpose' obligations (whenever issued), which include obligations issued directly by state and local governments or their agencies to fulfill essential governmental functions; (ii) certain obligations issued before August 8, 1986 for the benefit of non-governmental persons or entities; and (iii) certain 'private activity bonds' issued after August 7, 1986, which include 'qualified Section 501(c)(3) bonds' or refundings of certain obligations included in the second category. Opinions relating to the validity of municipal bonds, exclusion of municipal bond interest from an investor's gross income for federal income tax purposes and, where applicable, state and local income tax, are rendered by bond counsel to the issuing authorities at the time of issuance.

Interest on certain 'private activity bonds' (not including the bonds described in clause (iii) of the previous paragraph) issued after August 7, 1986 is exempt from regular federal income tax, but such interest (including a distribution by the Trust derived from such interest) is treated as a tax preference item that could subject the recipient to or increase the recipient's liability for the AMT.

The two principal classifications of municipal bonds are 'general obligation' and 'revenue' bonds. Issuers of general obligation bonds include states, counties, cities, towns and regional districts. The proceeds of these obligations are used to fund a wide range of public projects, including the construction or improvement of schools, highways and roads, water and sewer systems and a variety of other public purposes. The basic security of general obligation bonds is the issuer's pledge of its faith, credit, and taxing power for the payment of principal and interest. The taxes that can be levied for the payment of debt service may be limited or unlimited as to rate and amount.

Typically, the only security for a limited obligation or revenue bond is the net revenue derived from a particular facility or class of facilities financed thereby or, in some cases, from the proceeds of a special tax or other special revenues. Revenue bonds have been issued to fund a wide variety of revenue-producing public capital projects including: electric, gas, water and sewer systems; highways, bridges and tunnels; port and airport facilities; colleges and universities; hospitals; and convention, recreational, tribal gaming and housing facilities. Although the security behind these bonds varies widely, many lower rated bonds provide additional security in the form of a debt service reserve fund that may also be used to make principal and interest payments on the issuer's obligations. In addition, some revenue obligations (as well as general obligations) are insured by a bond insurance company or backed by a letter of credit issued by a banking institution. Revenue bonds also include, for example, pollution control, health care and housing bonds, which, although nominally issued by municipal authorities, are generally not secured by the taxing power of the municipality but by the revenues of the authority derived from payments by the private entity that owns or operates the facility financed with the proceeds of the bonds. Obligations of housing finance authorities have a wide range of security features, including reserve funds and insured or subsidized mortgages, as well as the net revenues from housing or other public projects. Many of these bonds do not generally constitute the pledge of the credit of the issuer of such bonds. The credit quality of such revenue bonds is usually directly related to the credit standing of the user of the facility being financed or of an

Eaton Vance National Municipal Opportunities Trust 2 SAI dated July 22, 2021

institution which provides a guarantee, letter of credit or other credit enhancement for the bond issue. The Trust may on occasion acquire revenue bonds that carry warrants or similar rights covering equity securities. Such warrants or rights may be held indefinitely, but if exercised, the Trust anticipates that it would, under normal circumstances, dispose of any equity securities so acquired within a reasonable period of time. Investing in revenue bonds may involve (without limitation) the following risks.

Hospital bond ratings are often based on feasibility studies that contain projections of expenses, revenues and occupancy levels. A hospital's income available to service its debt may be influenced by demand for hospital services, management capabilities, the service area economy, efforts by insurers and government agencies to limit rates and expenses, competition, availability and expense of malpractice insurance, and Medicaid and Medicare funding.

Education-related bonds are comprised of two types: (i) those issued to finance projects for public and private colleges and universities, charter schools and private schools, and (ii) those representing pooled interests in student loans. Bonds issued to supply educational institutions with funding are subject to many risks, including the risks of unanticipated revenue decline, primarily the result of decreasing student enrollment, decreasing state and federal funding, or changes in general economic conditions. Additionally, higher than anticipated costs associated with salaries, utilities, insurance or other general expenses could impair the ability of a borrower to make annual debt service payments. Student loan revenue bonds are generally offered by state (or sub-state) authorities or commissions and are backed by pools of student loans. Underlying student loans may be guaranteed by state guarantee agencies and may be subject to reimbursement by the United States Department of Education through its guaranteed student loan program. Others may be private, uninsured loans made to parents or students that may be supported by reserves or other forms of credit enhancement. Cash flows supporting student loan revenue bonds are impacted by numerous factors, including the rate of student loan defaults, seasoning of the loan portfolio, and student repayment deferral periods of forbearance. Other risks associated with student loan revenue bonds include potential changes in federal legislation regarding student loan revenue bonds, state guarantee agency reimbursement and continued federal interest and other program subsidies currently in effect.

Transportation debt may be issued to finance the construction of airports, toll roads, highways, or other transit facilities. Airport bonds are dependent on the economic conditions of the airport's service area and may be affected by the business strategies and fortunes of specific airlines. They may also be subject to competition from other airports and modes of transportation. Air traffic generally follows broader economic trends and is also affected by the price and availability of fuel. Toll road bonds are also affected by the cost and availability of fuel as well as toll levels, the presence of competing roads and the general economic health of an area. Fuel costs, transportation taxes and fees, and availability of fuel also affect other transportation-related securities, as do the presence of alternate forms of transportation, such as public transportation.

Industrial development bonds ('IDBs') are normally secured only by the revenues from the project and not by state or local government tax payments, they are subject to a wide variety of risks, many of which relate to the nature of the specific project. Generally, IDBs are sensitive to the risk of a slowdown in the economy.

Electric utilities face problems in financing large construction programs in an inflationary period, cost increases and delay occasioned by safety and environmental considerations (particularly with respect to nuclear facilities), difficulty in obtaining fuel at reasonable prices, and in achieving timely and adequate rate relief from regulatory commissions, effects of energy conservation and limitations on the capacity of the capital market to absorb utility debt.

Water and sewer revenue bonds are generally secured by the fees charged to each user of the service. The issuers of water and sewer revenue bonds generally enjoy a monopoly status and latitude in their ability to raise rates. However, lack of water supply due to insufficient rain, run-off, or snow pack can be a concern and has led to past defaults. Further, public resistance to rate increases, declining numbers of customers in a particular locale, costly environmental litigation, and federal environmental mandates are challenges faced by issuers of water and sewer bonds.

Standard tobacco bonds are secured by a single source of revenue, installment payments made by tobacco companies stemming from the settlement of lawsuits brought against them by various states (the 'Master Settlement Agreement'). Appropriation backed tobacco bonds are supported by the same Master Settlement Agreement payments as standard tobacco bonds, but are also subject to a state's pledge that the governor will request an appropriation of funds in its annual budget for debt service if Master Settlement Agreement revenues are insufficient. These payments are not generally fixed but rather are tied to the volume of the company's U.S. sales of cigarettes. Tobacco bonds are subject to several risks, including the risk that cigarette consumption declines or that a tobacco company defaults on its obligation to make payments to the state. Escrowed tobacco bonds no longer rely on Master Settlement Agreement revenue as security, and are backed by a variety of government securities.

Certain tax-exempt bonds issued by Native American tribes may be subject to the risk that a taxing authority would determine that the income from such bonds is not eligible for tax-exempt status. In the event of any final adverse ruling to this effect, holders of such bonds may be subject to penalties.

Eaton Vance National Municipal Opportunities Trust 3 SAI dated July 22, 2021

The obligations of any person or entity to pay the principal of and interest on a municipal obligation are subject to the provisions of bankruptcy, insolvency and other laws affecting the rights and remedies of creditors, such as the Federal Bankruptcy Act, and laws, if any, that may be enacted by Congress or state legislatures extending the time for payment of principal or interest, or both, or imposing other constraints upon enforcement of such obligations. Certain bond structures may be subject to the risk that a taxing authority may issue an adverse ruling regarding tax-exempt status. There is also the possibility that as a result of adverse economic conditions (including unforeseen financial events, natural disasters and other conditions that may affect an issuer's ability to pay its obligations), litigation or other conditions, the power or ability of any person or entity to pay when due principal of and interest on a municipal obligation may be materially affected or interest and principal previously paid may be required to be refunded. There have been instances of defaults and bankruptcies involving municipal obligations that were not foreseen by the financial and investment communities. The Trust will take whatever action it considers appropriate in the event of anticipated financial difficulties, default or bankruptcy of either the issuer of any municipal obligation or of the underlying source of funds for debt service. Such action may include: (i) retaining the services of various persons or firms (including affiliates of the investment adviser) to evaluate or protect any real estate, facilities or other assets securing any such obligation or acquired by the Trust as a result of any such event; (ii) managing (or engaging other persons to manage) or otherwise dealing with any real estate, facilities or other assets so acquired; and (iii) taking such other actions as the adviser (including, but not limited to, payment of operating or similar expenses of the underlying project) may deem appropriate to reduce the likelihood or severity of loss on the fund's investment. The Trust will incur additional expenditures in taking protective action with respect to portfolio obligations in (or anticipated to be in) default and assets securing such obligations.

Historically, municipal bankruptcies have been rare and certain provisions of the U.S. Bankruptcy Code governing such bankruptcy are unclear. Further, the application of state law to municipal obligation issuers could produce varying results among the states or among municipal obligation issuers within a state. These uncertainties could have a significant impact on the prices of the municipal obligations in which the Trust invests. There could be economic, business or political developments or court decisions that adversely affect all municipal obligations in the same sector. Developments such as changes in healthcare regulations, environmental considerations related to construction, construction cost increases and labor problems, failure of healthcare facilities to maintain adequate occupancy levels, and inflation can affect municipal obligations in the same sector. As the similarity in issuers of municipal obligations held by the Trust increases, the potential for fluctuations in the Trust's share price also may increase.

The Commonwealth of Puerto Rico and its related issuers are currently experiencing financial difficulties, including persistent government budget deficits, underfunded public pension benefit obligations, underfunded government retirement systems, sizable debt service obligations and a high unemployment rate. Several rating agencies have downgraded a number of securities issued in Puerto Rico to below investmentgrade, and numerous issuers have entered Title III of the Puerto Rico Oversite, Management and Economic Stability Act ('PROMESA'), which is similar to bankruptcy protection, through which the Commonwealth of Puerto Rico can restructure its debt. However, Puerto Rico's case is the first ever heard under PROMESA and there is no existing case precedent to guide the proceedings. Accordingly, Puerto Rico's debt restructuring process could take significantly longer than traditional municipal bankruptcy proceedings. Further, it is not clear whether a debt restructuring process will ultimately be approved or, if so, the extent to which it will apply to Puerto Rico municipal securities sold by an issuer other than the territory. A debt restructuring could reduce the principal amount due, the interest rate, the maturity, and other terms of Puerto Rico municipal securities, which could adversely affect the value of Puerto Rican municipal securities. Further legislation by the U.S. Congress, or actions by the oversight board established by PROMESA, or court approval of a debt restructuring deal could have a negative impact on the marketability, liquidity, or value of certain investments held by the Fund and could reduce the Fund's performance.

In addition, Puerto Rico has faced significant out-migration relating to its economic difficulties, eroding the Commonwealth's economic base and creating additional further uncertainty regarding its ability to meet its future repayment obligations. The Puerto Rican constitution prioritizes general obligation bonds over revenue bonds, so that all tax revenues, even those pledged to revenue bondholders, can be applied first to general obligation bonds and other Commonwealth-guaranteed debt if other revenues are insufficient to satisfy such obligations.

The secondary market for some municipal obligations issued within a state (including issues that are privately placed with the Trust) is less liquid than that for taxable debt obligations or other more widely traded municipal obligations. No established resale market exists for certain of the municipal obligations in which the Trust may invest. The market for obligations rated below investment grade is also likely to be less liquid than the market for higher rated obligations. As a result, the Trust may be unable to dispose of these municipal obligations at times when it would otherwise wish to do so at the prices at which they are valued.

Eaton Vance National Municipal Opportunities Trust 4 SAI dated July 22, 2021

Municipal obligations that are rated below investment grade but that, subsequent to the assignment of such rating, are backed by escrow accounts containing U.S. Government obligations may be determined by the investment adviser to be of investment grade quality for purposes of the Trust's investment policies. In the case of a defaulted obligation, the Trust may incur additional expense seeking recovery of its investment. Defaulted obligations are denoted in the 'Portfolio of Investments' in the 'Financial Statements' included in the Trust's reports to shareholders.

The yields on municipal obligations depend on a variety of factors, including purposes of the issue and source of funds for repayment, general money market conditions, general conditions of the municipal bond market, size of a particular offering, maturity of the obligation and rating of the issue. The ratings of Moody's, S&P and Fitch represent their opinions as to the quality of the municipal obligations which they undertake to rate, and in the case of insurers, other factors including the claims-paying ability of such insurer. It should be emphasized, however, that ratings are based on judgment and are not absolute standards of quality. Consequently, municipal obligations with the same maturity, coupon and rating may have different yields while obligations of the same maturity and coupon with different ratings may have the same yield. In addition, the market price of such obligations will normally fluctuate with changes in interest rates, and therefore the net asset value of the Trust will be affected by such changes.

State Specific Investments. If the Trust invests 25% or more of its gross assets in any one state (or U.S. territory), the Trust may be more susceptible to adverse economic, political or regulatory occurrences affecting a particular state (or U.S. territory). Municipal obligations of issuers located in a single state may be adversely affected by economic developments (including insolvency of an issuer) and by legislation and other governmental activities in that state. There could be economic, business or political developments or court decisions that adversely affect all municipal obligations in the same sector. In particular, investments in revenue bonds might involve (without limitation) the following risks. For purposes of this policy, the Trust's investments in pre-refunded municipal obligations that are fully backed as to payment of principal and interest by a pledge to an independent escrow agent of U.S. Government securities shall not count as obligations of an issuer located in a particular state. The Commonwealth of Puerto Rico and its related issuers continue to experience financial difficulties. See 'Municipal Obligations' above.

Insured Obligations. The Trust may purchase municipal obligations insured as to their scheduled payment of principal and interest or municipal obligations that are additionally secured by bank credit agreements or escrow accounts.

The credit quality of companies that provide such credit enhancements will affect the value of those securities. Although the insurance feature may reduce certain financial risks, the premiums for insurance and the higher market price sometimes paid for insured obligations may reduce the Trust's current yield. See Appendix A for a description of the claims-paying ability ratings of S&P and Moody's. The insurance does not guarantee the market value of the insured obligation or the NAV of the Trust's shares. To the extent that securities held by the Trust are insured as to principal and interest payments by insurers whose claims-paying ability rating is downgraded by Moody's, S&P or Fitch, the value of such securities may be affected.

Credit Quality. While municipal obligations rated investment grade or below and comparable unrated municipal obligations may have some quality and protective characteristics, these characteristics can be expected to be offset or outweighed by uncertainties or major risk exposures to adverse conditions. Lower rated and comparable unrated municipal obligations are subject to the risk of an issuer's inability to meet principal and interest payments on the obligations (credit risk) and may also be subject to greater price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity (market risk). Lower rated or unrated municipal obligations are also more likely to react to real or perceived developments affecting market and credit risk than are more highly rated obligations, which react primarily to movements in the general level of interest rates.

Municipal obligations held by the Trust which are rated below investment grade but which, subsequent to the assignment of such rating, are backed by escrow accounts containing U.S. Government obligations may be determined by the investment adviser to be of investment grade quality for purposes of the Trust's investment policies. The Trust may retain in its portfolio an obligation whose rating drops after its acquisition, including defaulted obligations, if such retention is considered desirable by the investment adviser; provided, however, that holdings of obligations rated below Baa or BBB will be less than 30% of the Trust's investments in municipal obligations and holdings rated below B- by Standard & Poor's or Fitch or B3 by Moody's will be less than 5% of its municipal obligations investments, each at the time of purchase. In the case of a defaulted obligation, the Trust may incur additional expense seeking recovery of its investment. See 'Portfolio of Investments' in the 'Financial Statements' incorporated by reference into this SAI with respect to any defaulted obligations held by the Trust.

When the Trust invests in lower rated or unrated municipal obligations, the achievement of the Trust's goals is more dependent on the investment adviser's ability than would be the case if the Trust were investing in municipal obligations in the higher rating categories. In evaluating the credit quality of a particular issue, whether rated or unrated, the investment adviser may take into consideration, among other things, the financial resources of the issuer (or, as appropriate, of the underlying source of funds for debt service), its sensitivity to economic conditions and trends, any operating history of and

Eaton Vance National Municipal Opportunities Trust 5 SAI dated July 22, 2021

the community support for the facility financed by the issue, the ability of the issuer's management and regulatory matters. The investment adviser may also purchase structured derivative products with greater or lesser credit risk than the underlying bonds. Such bonds may be rated investment grade, as well as below investment grade. For a description of municipal bond ratings, see Appendix A.

Municipal Leases. The Trust may invest in municipal lease obligations and certificates of participation, which arrangements frequently involve special risks. A municipal lease obligation is a bond that is secured by lease payments made by the party, typically a state or municipality, leasing the facilities (e.g., schools or office buildings) that were financed by the bond. Such lease payments may be subject to annual appropriation or may be made only from revenues associated with the facility financed. In other cases, the leasing state or municipality is obligated to appropriate funds from its general tax revenues to make lease payments as long as it utilizes the leased property. A certificate of participation (also referred to as a 'participation') in a municipal lease is an instrument evidencing a pro rata share in a specific pledged revenue stream, usually lease payments by the issuer that are typically subject to annual appropriation. The certificate generally entitles the holder to receive a share, or participation, in the payments from a particular project. Municipal lease obligations and participations are subject to the risk that the legislative body will not make the necessary appropriation and the issuer will not otherwise be willing or able to meet its obligation.

MLOs and participations therein represent a type of financing that may not have the depth of marketability associated with more conventional securities and, as such, they may be less liquid than conventional securities. In the event the Trust acquires an unrated municipal lease obligation, the investment adviser will be responsible for determining the credit quality of such obligation on an ongoing basis, including an assessment of the likelihood that the lease may or may not be cancelled.

The ability of issuers of MLOs to make timely lease payments may be adversely impacted in general economic downturns and as relative governmental cost burdens are allocated and reallocated among federal, state and local governmental units. Such non-payment would result in a reduction of income from and value of the obligation. Issuers of MLOs might seek protection under the bankruptcy laws. In the event of bankruptcy of such an issuer, holders of MLOs could experience delays and limitations with respect to the collection of principal and interest on such MLOs and may not, in all circumstances, be able to collect all principal and interest to which it is entitled. To enforce its rights in the event of a default in lease payments, the Trust might take possession of and manage the assets securing the issuer's obligations on such securities or otherwise incur costs to protect its rights, which may increase the Trust's operating expenses and adversely affect the net asset value of the Trust. When the lease contains a non-appropriation clause, however, the failure to pay would not be a default and the Trust would not have the right to take possession of the assets. Any income derived from the Trust's ownership or operation of such assets may not be tax-exempt.

Zero Coupon and Deep Discount Bonds and Payment-in-Kind ('PIK') Securities. Zero coupon bonds are debt obligations that do not require the periodic payment of interest and are issued at a significant discount from face value. The discount approximates the total amount of interest the bonds will accrue and compound over the period until maturity at a rate of interest reflecting the market rate of the security at the time of purchase. The effect of owning debt obligations that do not make current interest payments is that a fixed yield is earned not only on the original investment but also, in effect, on all discount accretion during the life of the debt obligation. This implicit reinvestment of earnings at a fixed rate eliminates the risk of being unable to invest distributions at a rate as high as the implicit yield on the zero coupon bond, but at the same time eliminates the holder's ability to reinvest at higher rates in the future. Deep discount bonds also are issued at a discount from face value, but may make periodic interest payments at a below market interest rate.

Payment-in-kind securities ('PIKs') are debt obligations that pay 'interest' in the form of other debt obligations, instead of in cash. Each of these instruments is normally issued and traded at a deep discount from face value. Zero-coupon bonds, step-ups and PIKs allow an issuer to avoid or delay the need to generate cash to meet current interest payments and, as a result, may involve greater credit risk than bonds that pay interest currently or in cash. The Trust would be required to distribute the income on these instruments as it accrues, even though the Trust will not receive the income on a current basis or in cash. Thus, the Trust may have to sell other investments, including when it may not be advisable to do so, to make income distributions to its shareholders. PIKs and other obligations that do not pay regular income distributions may experience greater volatility in response to interest rate changes and issuer developments. PIKs generally carry higher interest rates compared to obligations that make cash payments of interest to reflect their payment deferral and increased credit risk. Even if accounting conditions are met for accruing income payable at a future date under a PIK, the issuer could still default when the collection date occurs at the maturity of or payment date for the PIK. PIKs may be difficult to value accurately because they involve ongoing judgments as to the collectability of the deferred payments and the value of any associated collateral. If the issuer of a PIK defaults the Trust may lose its entire investment. PIK interest has the effect of generating investment income and increasing the incentive fees, if any, payable at a compounding rate. Generally, the deferral of PIK interest increases the loan to value ratio.

Eaton Vance National Municipal Opportunities Trust 6 SAI dated July 22, 2021

Bonds and preferred stocks that make 'in-kind' payments and other securities that do not pay regular income distributions may experience greater volatility in response to interest rate changes and issuer developments. PIK securities generally involve significantly greater credit risk than coupon loans because the Trust receives no cash payments until the maturity date or a specified cash payment date. Even if accounting conditions are met for accruing income payable at a future date under a PIK bond, the issuer could still default when the collection date occurs at the maturity of or payment date for the PIK bond. PIK bonds may be difficult to value accurately because they involve ongoing judgments as to the collectability of the deferred payments and the value of any associated collateral. If the issuer of a PIK security defaults, the Trust may lose its entire investment.

The Trust is required to accrue income from zero coupon and deep discount bonds and PIK securities on a current basis, even though it does not receive that income currently in cash, and the Trust is required to distribute that income for each taxable year. Such distributions could reduce the Trust's cash position and require it to sell securities and incur a gain or loss at a time it may not otherwise want to in order to provide the cash necessary for these distributions.

When-Issued, Delayed Delivery and Forward Commitment Transactions. Securities may be purchased on a 'forward commitment,' 'when-issued' or 'delayed delivery' basis (meaning securities are purchased or sold with payment and delivery taking place in the future) in order to secure what is considered to be an advantageous price and yield at the time of entering into the transaction. When the Trust agrees to purchase such securities, it assumes the risk of any decline in value of the security from the date of the agreement to purchase. The Trust does not earn interest on the securities it has committed to purchase until they are paid for and delivered on the settlement date.

From the time of entering into the transaction until delivery and payment is made at a later date, the securities that are the subject of the transaction are subject to market fluctuations. In forward commitment, when-issued or delayed delivery transactions, if the seller or buyer, as the case may be, fails to consummate the transaction the counterparty may miss the opportunity of obtaining a price or yield considered to be advantageous. However, no payment or delivery is made until payment is received or delivery is made from the other party to the transaction.

The Trust will make commitments to purchase when-issued securities only with the intention of actually acquiring the securities, but may sell such securities before the settlement date if it is deemed advisable as a matter of investment strategy. The payment obligation and the interest rate that will be received on the securities are fixed at the time the Trust enters into the purchase commitment. When the Trust commits to purchase a security on a when-issued basis it records the transaction and reflects the value of the security in determining its net asset value. Securities purchased on a when-issued basis and the securities held by the Trust are subject to changes in value based upon the perception of the creditworthiness of the issuer and changes in the level of interest rates (i.e., appreciation when interest rates decline and depreciation when interest rates rise). Therefore, to the extent that the Trust remains substantially fully invested at the same time that it has purchased securities on a when-issued basis, there will be greater fluctuations in the Trust's net asset value than if it solely set aside cash to pay for when-issued securities.

Credit Derivatives. The Trust may invest in credit default swaps, total return swaps or credit options for hedging and other risk management purposes. In a credit default swap, the buyer of credit protection (or seller of credit risk) agrees to pay the counterparty a fixed, periodic premium for a specified term. In return, the counterparty agrees to pay a contingent payment to the buyer in the event of an agreed upon credit occurrence with respect to a particular reference instrument. In a total return swap, the buyer receives a periodic return equal to the total economic return of a specified security, securities or index, for a specified period of time. In return, the buyer pays the counterparty a variable stream of payments, typically based upon short term interest rates, possibly plus or minus an agreed upon spread. Credit options are options whereby the purchaser has the right, but not the obligation, to enter into a transaction involving either an asset with inherent credit risk or a credit derivative, at terms specified at the initiation of the option. Transactions in derivative instruments involve a risk of loss or depreciation due to: unanticipated adverse changes in securities prices, interest rates, indices, the other financial instruments' prices or currency exchange rates; the inability to close out a position; default by the counterparty; imperfect correlation between a position and the desired hedge; tax constraints on closing out positions; and portfolio management constraints on securities subject to such transactions. Derivative instruments may sometimes increase or leverage exposure to a particular market risk, thereby increasing price volatility. The counterparties to many derivatives transactions are investment banks (or, if recently restructured, formerly categorized as investment banks), an industry that has recently experienced higher than normal bankruptcies. The risk of counterparty default increases in the event such counterparties undergo bankruptcy or are otherwise part of an industry affected by increased bankruptcy activity.

Redemption, Demand and Put Features and Put Options. Issuers of municipal obligations reserve the right to call (redeem) the bond. If an issuer redeems securities held by the Trust during a time of declining interest rates, the Trust may not be able to reinvest the proceeds in securities providing the same investment return as the securities redeemed. Also, some bonds may have 'put' or 'demand' features that allow early redemption by the bondholder. Longer term fixed-rate bonds may give the holder a right to request redemption at certain times (often annually after the lapse of an intermediate term). These bonds are more defensive than conventional long term bonds (protecting to some degree against a rise in interest rates) while providing greater opportunity than comparable intermediate term bonds, because the Trust may retain the bond if interest rates decline.

Eaton Vance National Municipal Opportunities Trust 7 SAI dated July 22, 2021

Liquidity and Protective Put Options. The Trust may enter into a separate agreement with the seller of the security or some other person granting the Trust the right to put the security to the seller thereof or the other person at an agreed upon price. Such agreements are subject to the risk of default by the other party, although the Trust intends to limit this type of transaction to institutions (such as banks or securities dealers) that the Adviser believes present minimal credit risks and would engage in this type of transaction to facilitate portfolio liquidity or (if the seller so agrees) to hedge against rising interest rates. There is no assurance that this kind of put option will be available to the Trust or that selling institutions will be willing to permit the Trust to exercise a put to hedge against rising interest rates. The Trust does not expect to assign any value to any separate put option that may be acquired to facilitate portfolio liquidity, inasmuch as the value (if any) of the put will be reflected in the value assigned to the associated security; any put acquired for hedging purposes would be valued in good faith under methods or procedures established by the Trustees after consideration of all relevant factors, including its expiration date, the price volatility of the associated security, the difference between the market price of the associated security and the exercise price of the put, the creditworthiness of the issuer of the put and the market prices of comparable put options. Interest income generated by certain bonds having put or demand features may be taxable.

OTC Options. The Trust may enter into an agreement with a potential buyer of a municipal obligation that gives the buyer the right, but not the obligation, to purchase a municipal obligation held by the Trust at a particular price in the future and is commonly referred to as an over-the-counter option or OTC option. Such agreements will be entered solely to help facilitate the selling of municipal obligations, for instance, if the buyer wishes to lock in a price for a particular municipal obligation subject to performing due diligence on the issue or issuer. The buyer may not pay a premium for such option. There is a risk that the value of a municipal obligation underlying an option may appreciate above the value that the buyer has agreed to pay for the municipal obligation and therefore the Trust would not be entitled to the appreciation above such price.

Variable and Floating Rate Debt Instruments. Variable rate instruments provide for adjustments in the interest rate at specified intervals (daily, weekly, monthly, semiannually, etc.) based on market conditions, credit ratings or interest rates and the investor may have the right to 'put' the security back to the issuer or its agent. Variable rate obligations normally provide that the holder can demand payment of the obligation on short notice at par with accrued interest and which are frequently secured by letters of credit or other support arrangements provided by banks. To the extent that such letters of credit or other arrangements constitute an unconditional guarantee of the issuer's obligations, a bank may be treated as the issuer of a security for the purposes of complying with the diversification requirements set forth in Section 5(b) of the 1940 Act and Rule 5b-2 thereunder. The Trust would anticipate using these bonds as cash equivalents pending longer term investment of its Trusts. The rate adjustment features tend to limit the extent to which the market value of the obligations will fluctuate.

Residual Interest Bonds. The Trust may invest in residual interests in a trust that holds municipal securities ('inverse floaters' also known as 'residual interest bonds'). The interest rate payable on an inverse floater bears an inverse relationship to the interest rate on another security issued by the trust. Because changes in the interest rate on the other security inversely affect the interest paid on the inverse floater, the value and income of an inverse floater is generally more volatile than that of a fixed rate bond. Inverse floaters have interest rate adjustment formulas that generally reduce or, in the extreme, eliminate the interest paid to the Trust when short-term interest rates rise, and increase the interest paid to the Trust when short-term interest rates fall. Inverse floaters have varying degrees of liquidity, and the market for these securities is relatively volatile. These securities tend to underperform the market for fixed rate bonds in a rising long-term interest rate environment, but tend to outperform the market for fixed rate bonds when long-term interest rates decline. Although volatile, inverse floaters typically offer the potential for yields exceeding the yields available on fixed rate bonds with comparable credit quality and maturity. These securities usually permit the investor to convert the floating rate to a fixed rate (normally adjusted downward), and this optional conversion feature may provide a partial hedge against rising rates if exercised at an opportune time. While inverse floaters expose the Trust to leverage risk because they provide more than one dollar of bond market exposure for every dollar invested, they are not subject to the Trust's restrictions on borrowings.

A tender option bond trust typically can be collapsed or closed by the holder of the residual interest bonds (such as the Trust) or by the liquidity provider. Generally, because the Trust may act to collapse the tender option bond trust and receive the value of the residual interest bonds held by the Trust within seven days, such residual interest bonds are considered liquid securities when held by the Trust.

At the discretion of the Adviser, the Trust may enter into a so-called shortfall and forbearance agreement with respect to an inverse floater held by the Trust. The Trust generally may enter into such agreements (i) when the liquidity provider to the tender option bond trust requires such an agreement because the level of leverage in the tender option bond trust exceeds the level that the liquidity provider is willing support absent such an agreement; and/or (ii) to seek to prevent the liquidity provider from collapsing the tender option bond trust in the event that the municipal obligation held in the trust has declined in value. Such agreements commit the Trust to reimburse, upon the termination of the trust

Eaton Vance National Municipal Opportunities Trust 8 SAI dated July 22, 2021

issuing the inverse floater, the difference between the liquidation value of the underlying security (which is the basis of the inverse floater) and the principal amount due to the holders of the floating rate security issued in conjunction with the inverse floater. Such agreements may expose the Trust's other assets to losses. Absent a shortfall and forbearance agreement, the Trust would not be required to make such a reimbursement. If the Trust chooses not to enter into such an agreement, the inverse floater could be terminated and the Trust could incur a loss. Consistent with SEC staff guidance, the Trust will segregate or earmark liquid assets with its custodian on a mark-to-market basis to cover any such payment obligations to liquidity providers.

Interest Rate Swaps and Forward Rate Contracts. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interest, e.g., an exchange of fixed rate payments for floating rate payments. The Trust will only enter into interest rate swaps on a net basis, i.e., the two payment streams are netted out with the Trust receiving or paying, as the case may be, only the net amount of the two payments. The Trust may also enter forward rate contracts. Under these contracts, the buyer locks in an interest rate at a future settlement date. If the interest rate on the settlement date exceeds the lock rate, the buyer pays the seller the difference between the two rates. If the lock rate exceeds the interest rate on the settlement date, the seller pays the buyer the difference between the two rates. Any such gain received by the Trust would be taxable.

If the other party to an interest rate swap or forward rate contract defaults, the Trust's risk of loss consists of the net amount of payments that the Trust is contractually entitled to receive. The net amount of the excess, if any, of the Trust's obligations over its entitlements will be maintained in a segregated account by the Trust's custodian. The Trust will not enter into any interest rate swap or forward rate contract unless the claims-paying ability of the other party thereto is considered to be investment grade by the investment adviser. If there is a default by the other party to such a transaction, the Trust will have contractual remedies pursuant to the agreements related to the transaction. These instruments are traded in the over the counter market.

Cybersecurity Risk. With the increased use of technologies by Trust service providers to conduct business, such as the Internet, the Trust is susceptible to operational, information security and related risks. The Trust relies on communications technology, systems, and networks to engage with clients, employees, accounts, shareholders, and service providers, and a cyber incident may inhibit the Trust's ability to use these technologies. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber attacks include, but are not limited to, gaining unauthorized access to digital systems (e.g., through 'hacking' or malicious software coding) for purposes of misappropriating assets or sensitive information, corrupting data, or causing operational disruption. Cyber attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites. A denial-of-service attack is an effort to make network services unavailable to intended users, which could cause shareholders to lose access to their electronic accounts, potentially indefinitely. Employees and service providers also may not be able to access electronic systems to perform critical duties for the Trust, such as trading and NAV calculation, during a denial-of-service attack. There is also the possibility for systems failures due to malfunctions, user error and misconduct by employees and agents, natural disasters, or other foreseeable and unforeseeable events.

Because technology is consistently changing, new ways to carry out cyber attacks are always developing. Therefore, there is a chance that some risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the Trust's ability to plan for or respond to a cyber attack. Like other funds and business enterprises, the Trust and its service providers have experienced, and will continue to experience, cyber incidents consistently. In addition to deliberate cyber attacks, unintentional cyber incidents can occur, such as the inadvertent release of confidential information by the Trust or its service providers.

The Trust uses third party service providers who are also heavily dependent on computers and technology for their operations. Cybersecurity failures by or breaches of the Trust's investment adviser or administrator and other service providers (including, but not limited to, the custodian or transfer agent), and the issuers of securities in which the Trust invests, may disrupt and otherwise adversely affect their business operations. This may result in financial losses to the Trust, impede Trust trading, interfere with the Trust's ability to calculate its NAV, limit a shareholder's ability to purchase or redeem shares of the Trust or cause violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, litigation costs, or additional compliance costs. While many of the Trust's service providers have established business continuity plans and risk management systems intended to identify and mitigate cyber attacks, there are inherent limitations in such plans and systems, including the possibility that certain risks have not been identified. The Trust cannot control the cybersecurity plans and systems put in place by service providers to the Trust and issuers in which the Trust invests. The Trust and its shareholders could be negatively impacted as a result.

Eaton Vance National Municipal Opportunities Trust 9 SAI dated July 22, 2021

Illiquid Investments. Illiquid investments may include obligations legally restricted as to resale, and may include commercial paper issued pursuant to Section 4(a)(2) of the 1933 Act and securities eligible for resale pursuant to Rule 144A thereunder. Rule 144A securities may increase the level of portfolio illiquidity if eligible buyers become uninterested in purchasing such securities.

The secondary market for some municipal obligations issued within a state (including issues which are privately placed with the Trust) is less liquid than that for taxable debt obligations or other more widely traded municipal obligations. No established resale market exists for certain of the municipal obligations in which the Trust may invest. The market for obligations rated below investment grade is also likely to be less liquid than the market for higher rated obligations. As a result, the Trust may be unable to dispose of these municipal obligations at times when it would otherwise wish to do so at the prices at which they are valued.

At times, a portion of the Trust's assets may be invested in instruments as to which the Trust, by itself or together with other accounts managed by the Adviser and its affiliates, holds a major portion or all of such instruments. Under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Trust could find it more difficult to sell such instruments when the Adviser believes it advisable to do so or may be able to sell such instruments only at prices lower than if such instruments were more widely held. It may also be more difficult to determine the fair value of such instruments for purposes of computing the Trust's net asset value.

Futures Contracts and Options on Futures Contracts. A change in the level of interest rates may affect the value of the securities held by the Trust (or of securities that the Trust expects to purchase).The Trust may enter into (i) futures contracts for the purchase or sale of debt securities and (ii) futures contracts on securities indices. All futures contracts entered into by the Trust are traded on exchanges or boards of trade that are licensed and regulated by the U.S. Commodity Futures Trading Commission ('CFTC') and must be executed through a futures commission merchant or brokerage firm which is a member of the relevant exchange. The Trust may purchase and write call and put options on futures contracts which are traded on a United States exchange or board of trade. The Trust will be required, in connection with transactions in futures contracts and the writing of options on futures, to make margin deposits, which will be held by the futures commission merchant through whom the Trust engages in such futures and options transactions.

Some futures contracts and options thereon may become illiquid under adverse market conditions. In addition, during periods of market volatility, a commodity exchange may suspend or limit transactions in an exchange-traded instrument, which may make the instrument temporarily illiquid and difficult to price. Commodity exchanges may also establish daily limits on the amount that the price of a futures contract or futures option can vary from the previous day's settlement price. Once the daily limit is reached, no trades may be made that day at a price beyond the limit. This may prevent the Trust from closing out positions and limiting its losses.

The Trust will engage in futures and related options transactions for hedging purposes. The Trust will determine that the price fluctuations in the futures contracts and options on futures used for hedging purposes are substantially related to price fluctuations in securities held by the Trust or which it expects to purchase. The Trust will engage in transactions in futures and related options contracts only to the extent such transactions are consistent with the requirements of the Code, for maintaining qualification of the Trust as a regulated investment company for federal income tax purposes. The Trust has claimed an exclusion from the definition of a Commodity Pool Operator ('CPO') under the Commodity Exchange Act and therefore is not subject to registration or regulation as a CPO.

The regulation of derivatives has undergone substantial change in recent years. In particular, although many provisions of the Dodd-Frank Wall Street Reform and Consumer Protection Act (the 'Dodd-Frank Act') have yet to be fully implemented or are subject to phase-in periods, it is possible that upon implementation these provisions, or any future regulatory or legislative activity, could limit or restrict the ability of a Fund to use derivative instruments, including futures, options on futures and swap agreements as a part of its investment strategy, increase the costs of using these instruments or make them less effective. New position limits imposed on a Fund or its counterparty may also impact the Fund's ability to efficiently utilize futures, options, and swaps.

As of October 28, 2020, the SEC has adopted new regulations that may significantly alter a Fund's regulatory obligations with regard to its derivatives usage. In particular, the new regulations will, upon implementation, eliminate the current asset segregation framework for covering derivatives and certain other financial instruments, impose new responsibilities on the Board and establish new reporting and recordkeeping requirements for a Fund and may, depending on the extent to which a Fund uses derivatives, impose value at risk limitations on a Fund's use of derivatives, and require the Fund's Board to adopt a derivative risk management program. The implementation of these requirements may limit the ability of a Fund to use derivative instruments as part of its investment strategy, increase the costs of using these instruments or make them less effective. Limits or restrictions applicable to the counterparties with which a Fund engages in derivative transactions also could prevent the Fund from using these instruments or affect the pricing or other factors relating to these instruments, or may change the availability of certain investments. Legislation may be enacted that could negatively affect the assets of the Trust. Legislation or regulation may also change the way in which the Trust itself is regulated. The effects of any new governmental regulation cannot be predicted and there can be no assurance that any new governmental regulation will not adversely affect the Trust's performance or ability to achieve its investment objective(s).

Eaton Vance National Municipal Opportunities Trust 10 SAI dated July 22, 2021

LIBOR Transition and Associated Risk. The London Interbank Offered Rate ('LIBOR') is the average offered rate for various maturities of short-term loans between major international banks who are members of the British Bankers Association. LIBOR is the most common benchmark interest rate index used to make adjustments to variable-rate loans. It is used throughout global banking and financial industries to determine interest rates for a variety of financial instruments (such as debt instruments and derivatives) and borrowing arrangements, and to determine dividend rates for preferred shares. In July 2017, the Financial Conduct Authority (the 'FCA'), the United Kingdom financial regulatory body, announced a desire to phase out the use of LIBOR. The ICE Benchmark Administration Limited, the administrator of LIBOR, is expected to cease publishing certain LIBOR settings on December 31, 2021, and the remaining LIBOR settings on June 30, 2023. Many market participants are expected to transition to the use of alternative reference or benchmark rates before the end of 2021.

In June 2017, the Alternative Reference Rates Committee, a group of large U.S. banks working with the Federal Reserve, announced its selection of a new Secured Overnight Financing Rate ('SOFR'), which is intended to be a broad measure of secured overnight U.S. Treasury repo rates, as an appropriate replacement for LIBOR. The Federal Reserve Bank of New York began publishing the SOFR in 2018, with the expectation that it could be used on a voluntary basis in new instruments and transactions. Bank working groups and regulators in other countries have suggested other alternatives for their markets, including the Sterling Overnight Interbank Average Rate ('SONIA') in England.

Various financial industry groups are planning for the transition, but there are obstacles to converting certain longer term securities and transactions to a new benchmark. Although the transition process away from LIBOR is expected to be defined in advance of the anticipated discontinuation date, there remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate or rates. The transition process may involve, among other things, increased volatility or illiquidity in markets for instruments that currently rely on LIBOR. The transition may also result in a change in (i) the value of certain instruments held by the Fund, (ii) the cost of borrowing or the dividend rate for preferred shares, or (iii) the effectiveness of related Fund transactions such as hedges, as applicable. When LIBOR is discontinued, the LIBOR replacement rate may be lower than market expectations, which could have an adverse impact on the value of preferred and debt-securities with floating or fixed-to-floating rate coupons. Any such effects of the transition away from LIBOR, as well as other unforeseen effects, could result in losses to the Fund. Since the usefulness of LIBOR as a benchmark could deteriorate during the transition period, these effects may occur prior to the discontinuation date.

Additionally, while some existing LIBOR-based instruments may contemplate a scenario where LIBOR is no longer available by providing for an alternative or 'fallback' rate-setting methodology, there may be significant uncertainty regarding the effectiveness of any such alternative methodologies to replicate LIBOR. Not all existing LIBOR-based instruments have such fallback provisions, and many that do, do not contemplate the permanent cessation of LIBOR. While it is expected that market participants will amend legacy financial instruments referencing LIBOR to include fallback provisions to alternative reference rates, there remains uncertainty regarding the willingness and ability of parties to add or amend such fallback provisions in legacy instruments maturing after the end of 2021, particularly with respect to legacy cash products. Although there are ongoing efforts among certain government entities and other organizations to address these uncertainties, the ultimate effectiveness of such efforts in not yet known. Liquid markets for newly-issued instruments that use an alternative reference rate are still developing. Consequently, there may be challenges for a Fund to enter into hedging transactions against instruments tied to alternative reference rates until a market for such hedging transactions develops. Certain proposed replacement rates to LIBOR, such as SOFR, are materially different from LIBOR, and changes in the applicable spread for financial instruments transitioning away from LIBOR will need to be made to accommodate the differences. Furthermore, the risks associated with the expected discontinuation of LIBOR and transition to replacement rates may be exacerbated if an orderly transition to an alternative reference rate is not completed in a timely manner.

Asset Coverage Requirements. To the extent required by SEC guidance, if a transaction creates a future obligation of the Trust to another party the Trust will: (1) cover the obligation by entering into an offsetting position or transaction; and/or (2) segregate cash and/or liquid securities with a value (together with any collateral posted with respect to the obligation) at least equal to the marked-to-market value of the obligation. Assets used as cover or segregated cannot be sold while the position(s) requiring coverage is open unless replaced with other appropriate assets. As a result, if a large portion of assets is segregated or committed as cover, it could impede portfolio management. The types of transactions that may require asset coverage include (but are not limited to) forward contracts, certain options, forward commitments, futures contracts, when-issued securities, swap agreements and residual interest bonds.

Eaton Vance National Municipal Opportunities Trust 11 SAI dated July 22, 2021

Temporary Investments. The Trust may invest in cash equivalents to invest daily cash balances or for temporary defensive purposes. Cash equivalents are highly liquid, short-term securities such as commercial paper, time deposits, certificates of deposit, short-term notes and short-term U.S. Government obligations. These securities may be subject to federal income, state income and/or other taxes. During unusual market conditions, the Trust may invest up to 100% of its assets in cash or cash equivalents temporarily, which may be inconsistent with its investment objectives and other policies.

Portfolio Trading and Turnover Rate. A change in the securities held by the Trust is known as 'portfolio turnover' and generally involves expense to the Trust, including brokerage commissions or dealer markups and other transaction costs on both the sale of securities and the reinvestment of the proceeds in other securities. If sales of portfolio securities cause the Trust to realize net short-term capital gains, such gains will be taxable as ordinary income to taxable shareholders. Portfolio turnover rate for a fiscal year is the ratio of the lesser of purchases or sales of portfolio securities to the monthly average of the value of portfolio securities − excluding securities whose maturities at acquisition were one year or less. The Trust's portfolio turnover rate is not a limiting factor when the Adviser considers a change in the Trust's portfolio holdings. The portfolio turnover rate(s) for the Trust for the fiscal years ended March 31, 2021 and March 31, 2020 were 13% and 44%, respectively.

Diversified Status. The Trust is a 'diversified' investment company under the 1940 Act. This means that with respect to 75% of its total assets (1) it may not invest more than 5% of its total assets in the securities of any one issuer (except U.S. Government obligations) and (2) it may not own more than 10% of the outstanding voting securities of any one issuer. With respect to no more than 25% of its total assets, investments are not subject to the foregoing restrictions.

Investment Restrictions. The following investment restrictions of the Trust are designated as fundamental policies and as such cannot be changed without the approval of the holders of a majority of the Trust's outstanding voting securities, which as used in this SAI means the lesser of: (a) 67% of the shares of the Trust present or represented by proxy at a meeting if the holders of more than 50% of the outstanding shares are present or represented at the meeting; or (b) more than 50% of the outstanding shares of the Trust. As a matter of fundamental policy, the Trust may not:

(1) Borrow money, except as permitted by the Investment Company Act of 1940, as amended (the '1940 Act');
(2) Issue senior securities, as defined in the 1940 Act, other than (i) preferred shares which immediately after issuance will have asset coverage of at least 200%, (ii) indebtedness which immediately after issuance will have asset coverage of at least 300%, or (iii) the borrowings permitted by investment restriction (1) above;
(3) Purchase securities on margin (but the Trust may obtain such short-term credits as may be necessary for the clearance of purchases and sales of securities). The purchase of investment assets with the proceeds of a permitted borrowing or securities offering will not be deemed to be the purchase of securities on margin;
(4) Underwrite securities issued by other persons, except insofar as it may technically be deemed to be an underwriter under the Securities Act of 1933, as amended, in selling or disposing of a portfolio investment;
(5) Make loans to other persons, except by (a) the acquisition of loans, loan interests, debt securities and other obligations in which the Trust is authorized to invest in accordance with its investment objectives and policies, (b) entering into repurchase agreements, and (c) lending its portfolio securities;
(6) Purchase or sell real estate, although it may purchase and sell securities which are secured by interests in real estate and securities of issuers which invest or deal in real estate. The Trust reserves the freedom of action to hold and to sell real estate acquired as a result of the ownership of securities;
(7) Purchase or sell physical commodities or contracts for the purchase or sale of physical commodities. Physical commodities do not include futures contracts with respect to securities, securities indices or other financial instruments;
(8) Invest 25% or more of its total assets in any single industry or group of industries (other than securities issued or guaranteed by the U.S. government or its agencies or instrumentalities).
(9) With respect to 75% of its total assets, invest more than 5% of its total assets (taken at current value) in the securities of any one issuer, or invest in more than 10% of the outstanding voting securities of any one issuer, except obligations issued or guaranteed by the U.S. Government, its agencies or instrumentalities and except securities of other investment companies;

For purposes of the Trust's investment restrictions, the determination of the 'issuer' of a municipal obligation that is not a general obligation bond will be made by the Adviser on the basis of the characteristics of the obligation and other relevant factors, the most significant of which is the source of funds committed to meeting interest and principal payments of such obligation.

Eaton Vance National Municipal Opportunities Trust 12 SAI dated July 22, 2021

The Trust may borrow money as a temporary measure for extraordinary or emergency purposes, including the payment of dividends and the settlement of securities transactions which otherwise might require untimely dispositions of Trust securities. The 1940 Act currently requires that the Trust have 300% asset coverage with respect to all borrowings other than temporary borrowings.

In regard to restriction (5)(c), the value of the securities loaned by the Trust may not exceed 33 1/3% of its total assets.

For purposes of construing restriction (8), securities of the U.S. Government, its agencies, or instrumentalities are not considered to represent industries. Municipal obligations backed by the credit of a governmental entity are also not considered to represent industries. Furthermore, a large economic or market sector shall not be construed as a group of industries for purposes of this restriction.

The Trust has adopted the following nonfundamental investment policy which may be changed by the Trustees without approval of the Trust's shareholders. As a matter of nonfundamental policy, the Trust may not make short sales of securities or maintain a short position, unless at all times when a short position is open it either owns an equal amount of such securities or owns securities convertible into or exchangeable, without payment of any further consideration, for securities of the same issuer as, and equal in amount to, the securities sold short.

Upon Board's approval, the Trust may invest more than 10% of its total assets in one or more other management investment companies (or may invest in affiliated investment companies) to the extent permitted by the 1940 Act and rules thereunder.

Whenever an investment policy or investment restriction set forth in the Prospectus or this SAI states a maximum percentage of assets that may be invested in any security or other asset or describes a policy regarding quality standards, such percentage limitation or standard shall be determined immediately after and as a result of the Trust's acquisition of such security or asset. Accordingly, any later increase or decrease resulting from a change in values, assets or other circumstances will not compel the Trust to dispose of such security or other asset. Notwithstanding the foregoing, the Trust must always be in compliance with the borrowing policies set forth above.

TRUSTEES AND OFFICERS

The Board of Trustees of the Trust (the 'Board') is responsible for the overall management and supervision of the affairs of the Trust. The Board members and officers of the Trust are listed below. Except as indicated, each individual has held the office shown or other offices in the same company for the last five years. Each Trustee holds office until the annual meeting for the year in which his or her term expires and until his or her successor is elected and qualified, subject to a prior death, resignation, retirement, disqualification or removal. Under the terms of the Trust's current Trustee retirement policy, an Independent Trustee must retire and resign as a Trustee on the earlier of: (i) the first day of July following his or her 74th birthday; or (ii), with limited exception, December 31st of the 20th year in which he or she has served as a Trustee. However, if such retirement and resignation would cause the Trust to be out of compliance with Section 16 of the 1940 Act, as amended (the '1940 Act') or any other regulations or guidance of the Securities and Exchange Commission ('SEC'), then such retirement and resignation will not become effective until such time as action has been taken for the Trust to be in compliance therewith. The 'noninterested Trustees' consist of those Trustees who are not 'interested persons' of the Trust, as that term is defined under the 1940 Act. The business address of each Board member and officer is Two International Place, Boston, Massachusetts 02110. As used in this SAI, 'BMR' refers to Boston Management and Research, 'EVC' refers to Eaton Vance Corp., 'EV' refers to EV, LLC, 'Eaton Vance' or 'EVM' refers to Eaton Vance Management and 'EVD' refers to Eaton Vance Distributors, Inc. EV is the trustee of each of Eaton Vance and BMR. Effective March 1, 2021, each of Eaton Vance, BMR, EVD and EV are indirect wholly owned subsidiaries of Morgan Stanley. Each officer affiliated with Eaton Vance may hold a position with other Eaton Vance affiliates that is comparable to his or her position with Eaton Vance listed below.

Eaton Vance National Municipal Opportunities Trust 13 SAI dated July 22, 2021
Name and Year of Birth Trust
Position(s)(1)
Length of Service Principal Occupation(s) During Past Five Years
and Other Relevant Experience
Number of Portfolios
in Fund Complex
Overseen By
Trustee(2)
Other Directorships Held
During Last Five Years
Interested Trustee
THOMAS E. FAUST JR.
1958
Class I
Trustee
Until 2022. 3 years.
Since 2007.
Chairman of Morgan Stanley Investment Management, Inc. (MSIM), member of the Board of Managers and President of EV, Chief Executive Officer and President of Eaton Vance and BMR, and Director of EVD. Formerly, Chairman, Chief Executive Officer and President of EVC. Trustee and/or officer of 138 registered investment companies. Mr. Faust is an interested person because of his positions with MSIM, BMR, Eaton Vance, EVD and EV, which are affiliates of the Trust, and his former position with EVC, which was an affiliate of the Trust prior to March 1, 2021. 138 Formerly, Director of EVC (2007-2021) and Hexavest Inc. (2012-2021) (investment management firm).
Noninterested Trustees
MARK R. FETTING
1954
Class III
Trustee
Until 2024. 3 Years.
Since 2016.
Private investor. Formerly held various positions at Legg Mason, Inc. (investment management firm) (2000-2012), including President, Chief Executive Officer, Director and Chairman (2008-2012), Senior Executive Vice President (2004-2008) and Executive Vice President (2001-2004). Formerly, President of Legg Mason family of funds (2001-2008). Formerly, Division President and Senior Officer of Prudential Financial Group, Inc. and related companies (investment management firm) (1991-2000). 139 None
CYNTHIA E. FROST
1961
Class II
Trustee
Until 2023. 3 Years.
Since 2014.
Private investor. Formerly, Chief Investment Officer of Brown University (university endowment) (2000-2012). Formerly, Portfolio Strategist for Duke Management Company (university endowment manager) (1995-2000). Formerly, Managing Director, Cambridge Associates (investment consulting company) (1989-1995). Formerly, Consultant, Bain and Company (management consulting firm) (1987-1989). Formerly, Senior Equity Analyst, BA Investment Management Company (1983-1985). 138 None
Eaton Vance National Municipal Opportunities Trust 14 SAI dated July 22, 2021
Name and Year of Birth Trust
Position(s)(1)
Length of Service Principal Occupation(s) During Past Five Years
and Other Relevant Experience
Number of Portfolios
in Fund Complex
Overseen By
Trustee(2)
Other Directorships Held
During Last Five Years
GEORGE J. GORMAN
1952
Chairperson of the Board and Class III
Trustee
Until 2024. 3 Years.
Chairperson of the Board since 2021 and Trustee since 2014.
Principal at George J. Gorman LLC (consulting firm). Formerly, Senior Partner at Ernst & Young LLP (a registered public accounting firm) (1974-2009). 139 None
VALERIE A. MOSLEY
1960
Class I
Trustee
Until 2022. 3 Years.
Since 2014.
Chairwoman and Chief Executive Officer of Valmo Ventures (a consulting and investment firm). Founder of Upward Wealth, Inc., dba BrightUP, a fintech platform. Formerly, Partner and Senior Vice President, Portfolio Manager and Investment Strategist at Wellington Management Company, LLP (investment management firm) (1992-2012). Formerly, Chief Investment Officer, PG Corbin Asset Management (1990-1992). Formerly worked in institutional corporate bond sales at Kidder Peabody (1986-1990). 139 Director of DraftKings, Inc. (digital sports entertainment and gaming company) (since September 2020). Director of Groupon, Inc. (e-commerce provider) (since April 2020). Director of Envestnet, Inc. (provider of intelligent systems for wealth management and financial wellness) (since 2018). Formerly, Director of Dynex Capital, Inc. (mortgage REIT) (2013-2020).
WILLIAM H. PARK
1947
Class II
Trustee
Until 2023. 3 Years. Since 2003. Private investor. Formerly, Consultant (management and transactional) (2012-2014). Formerly, Chief Financial Officer, Aveon Group, L.P. (investment management firm) (2010-2011). Formerly, Vice Chairman, Commercial Industrial Finance Corp. (specialty finance company) (2006-2010). Formerly, President and Chief Executive Officer, Prizm Capital Management, LLC (investment management firm) (2002-2005). Formerly, Executive Vice President and Chief Financial Officer, United Asset Management Corporation (investment management firm) (1982-2001). Formerly, Senior Manager, Price Waterhouse (now PricewaterhouseCoopers) (a registered public accounting firm) (1972-1981). 139 None
Eaton Vance National Municipal Opportunities Trust 15 SAI dated July 22, 2021
Name and Year of Birth Trust
Position(s)(1)
Length of Service Principal Occupation(s) During Past Five Years
and Other Relevant Experience
Number of Portfolios
in Fund Complex
Overseen By
Trustee(2)
Other Directorships Held
During Last Five Years
HELEN FRAME PETERS
1948

Class III
Trustee
Until 2024. 3 Years.
Since 2008.
Professor of Finance, Carroll School of Management, Boston College. Formerly, Dean, Carroll School of Management, Boston College (2000-2002). Formerly, Chief Investment Officer, Fixed Income, Scudder Kemper Investments (investment management firm) (1998-1999). Formerly, Chief Investment Officer, Equity and Fixed Income, Colonial Management Associates (investment management firm) (1991-1998). 139 None
KEITH QUINTON
1958
Class II
Trustee
Until 2023. 3 Years.
Since 2018.
Private investor, researcher and lecturer. Formerly, Independent Investment Committee Member at New Hampshire Retirement System (2017-2021). Formerly, Portfolio Manager and Senior Quantitative Analyst at Fidelity Investments (investment management firm) (2001-2014). 139 Formerly, Director (2016-2021) and Chairman (2019-2021) of New Hampshire Municipal Bond Bank.
MARCUS L. SMITH
1966
Class III
Trustee
Until 2024. 3 Years.
Since 2018.
Private investor. Formerly, Portfolio Manager at MFS Investment Management (investment management firm) (1994-2017). 139 Director of First Industrial Realty Trust, Inc. (an industrial REIT) (since 2021). Director of MSCI Inc. (global provider of investment decision support tools) (since 2017). Formerly, Director of DCT Industrial Trust Inc. (logistics real estate company) (2017-2018).
SUSAN J. SUTHERLAND
1957
Class II
Trustee
Until 2023. 3 years.
Since 2015.
Private investor. Director of Ascot Group Limited and certain of its subsidiaries (insurance and reinsurance) (since 2017). Formerly, Director of Hagerty Holding Corp. (insurance) (2015-2018) and Montpelier Re Holdings Ltd. (insurance and reinsurance) (2013-2015). Formerly, Associate, Counsel and Partner at Skadden, Arps, Slate, Meagher & Flom LLP (law firm) (1982-2013). 139 Director of Kairos Acquisition Corp. (insurance/InsurTech acquisition company) (since 2021).
SCOTT E. WENNERHOLM
1959
Class I
Trustee
Until 2022. 3 years.
Since 2016.
Private investor. Formerly, Trustee at Wheelock College (postsecondary institution) (2012-2018). Formerly, Consultant at GF Parish Group (executive recruiting firm) (2016-2017). Formerly, Chief Operating Officer and Executive Vice President at BNY Mellon Asset Management (investment management firm) (2005-2011). Formerly, Chief Operating Officer and Chief Financial Officer at Natixis Global Asset Management (investment management firm) (1997-2004). Formerly, Vice President at Fidelity Investments Institutional Services (investment management firm) (1994-1997). 139 None
(1) The Board of Trustees is divided into three classes, each class having a term of three years to expire on the date of the third annual meeting following its election.
(2) Includes both funds and portfolios in a hub and spoke structure.
Eaton Vance National Municipal Opportunities Trust 16 SAI dated July 22, 2021
Principal Officers who are not Trustees
Name and Year of Birth Trust Position(s) Length of Service Principal Occupation(s) During Past Five Years
ERIC A. STEIN
1980
President Since 2020 Vice President and Chief Investment Officer, Fixed Income of Eaton Vance and BMR. Prior to November 1, 2020, Mr. Stein was a co-Director of Eaton Vance's Global Income Investments. Officer of 117 registered investment companies managed by Eaton Vance or BMR. Also Vice President of Calvert Research and Management ('CRM') since 2020.
DEIDRE E. WALSH
1971
Vice President and Chief Legal Officer Since 2021

Vice President of Eaton Vance and BMR. Officer of 139 registered investment companies managed by Eaton Vance or BMR. Also Vice President of CRM and

officer of 39 registered investment companies advised or administered by CRM since 2021.

KIMBERLY M. ROESSIGER
1985
Secretary Since 2021 Vice President of Eaton Vance and BMR. Officer of 139 registered investment companies managed by Eaton Vance or BMR.
JAMES F. KIRCHNER
1967
Treasurer Since 2013 Vice President of Eaton Vance and BMR. Officer of 139 registered investment companies managed by Eaton Vance or BMR. Also Vice President of CRM and officer of 39 registered investment companies advised or administered by CRM since 2016.
RICHARD F. FROIO
1968
Chief Compliance Officer Since 2017 Vice President of Eaton Vance and BMR since 2017. Officer of 139 registered investment companies managed by Eaton Vance or BMR. Formerly, Deputy Chief Compliance Officer (Adviser/Funds) and Chief Compliance Officer (Distribution) at PIMCO (2012-2017) and Managing Director at BlackRock/Barclays Global Investors (2009-2012).

The Board has general oversight responsibility with respect to the business and affairs of the Trust. The Board has engaged an investment adviser and (if applicable) a sub-adviser(s) (collectively the 'adviser') to manage the Trust and an administrator to administer the Trust and is responsible for overseeing such adviser and administrator and other service providers to the Trust. The Board is currently composed of eleven Trustees, including ten Trustees who are not 'interested persons' of the Trust, as that term is defined in the 1940 Act (each a 'noninterested Trustee'). In addition to six regularly scheduled meetings per year, the Board holds special meetings or informal conference calls to discuss specific matters that may require action prior to the next regular meeting. As discussed below, the Board has established six committees to assist the Board in performing its oversight responsibilities.

The Board has appointed a noninterested Trustee to serve in the role of Chairperson. The Chairperson's primary role is to participate in the preparation of the agenda for meetings of the Board and the identification of information to be presented to the Board with respect to matters to be acted upon by the Board. The Chairperson also presides at all meetings of the Board and acts as a liaison with service providers, officers, attorneys, and other Board members generally between meetings. The Chairperson may perform such other functions as may be requested by the Board from time to time. In addition, the Board may appoint a noninterested Trustee to serve in the role of Vice-Chairperson. The Vice-Chairperson has the power and authority to perform any or all of the duties and responsibilities of the Chairperson in the absence of the Chairperson and/or as requested by the Chairperson. Except for any duties specified herein or pursuant to the Trust's Declaration of Trust or By-laws, the designation of Chairperson or Vice-Chairperson does not impose on such noninterested Trustee any duties, obligations or liability that is greater than the duties, obligations or liability imposed on such person as a member of the Board, generally.

Eaton Vance National Municipal Opportunities Trust 17 SAI dated July 22, 2021

The Trust is subject to a number of risks, including, among others, investment, compliance, operational, and valuation risks. Risk oversight is part of the Board's general oversight of the Trust and is addressed as part of various activities of the Board and its Committees. As part of its oversight of the Trust, the Board directly, or through a Committee, relies on and reviews reports from, among others, Trust management, the adviser, the administrator, the principal underwriter, the Chief Compliance Officer (the 'CCO'), and other Trust service providers responsible for day-to-day oversight of Trust investments, operations and compliance to assist the Board in identifying and understanding the nature and extent of risks and determining whether, and to what extent, such risks can or should be mitigated. The Board also interacts with the CCO and with senior personnel of the adviser, administrator, principal underwriter and other Trust service providers and provides input on risk management issues during meetings of the Board and its Committees. Each of the adviser, administrator, principal underwriter and the other Trust service providers has its own, independent interest and responsibilities in risk management, and its policies and methods for carrying out risk management functions will depend, in part, on its individual priorities, resources and controls. It is not possible to identify all of the risks that may affect the Trust or to develop processes and controls to eliminate or mitigate their occurrence or effects. Moreover, it is necessary to bear certain risks (such as investment-related risks) to achieve the Trust's goals.

The Board, with the assistance of management and with input from the Board's various committees, reviews investment policies and risks in connection with its review of Trust performance. The Board has appointed a Trust CCO who oversees the implementation and testing of the Trust compliance program and reports to the Board regarding compliance matters for the Trust and its principal service providers. In addition, as part of the Board's periodic review of the advisory, subadvisory (if applicable), distribution and other service provider agreements, the Board may consider risk management aspects of their operations and the functions for which they are responsible. With respect to valuation, the Board approves and periodically reviews valuation policies and procedures applicable to valuing the Trust's shares. The administrator, the investment adviser and the sub-adviser (if applicable) are responsible for the implementation and day-to-day administration of these valuation policies and procedures and provides reports to the Audit Committee of the Board and the Board regarding these and related matters. In addition, the Audit Committee of the Board or the Board receives reports periodically from the independent public accounting firm for the Trust regarding tests performed by such firm on the valuation of all securities, as well as with respect to other risks associated with mutual funds. Reports received from service providers, legal counsel and the independent public accounting firm assist the Board in performing its oversight function.

The Trust's Declaration of Trust does not set forth any specific qualifications to serve as a Trustee. The Charter of the Governance Committee also does not set forth any specific qualifications, but does set forth certain factors that the Committee may take into account in considering noninterested Trustee candidates. In general, no one factor is decisive in the selection of an individual to join the Board. Among the factors the Board considers when concluding that an individual should serve on the Board are the following: (i) knowledge in matters relating to the mutual fund industry; (ii) experience as a director or senior officer of public companies; (iii) educational background; (iv) reputation for high ethical standards and professional integrity; (v) specific financial, technical or other expertise, and the extent to which such expertise would complement the Board members' existing mix of skills, core competencies and qualifications; (vi) perceived ability to contribute to the ongoing functions of the Board, including the ability and commitment to attend meetings regularly and work collaboratively with other members of the Board; (vii) the ability to qualify as a noninterested Trustee for purposes of the 1940 Act and any other actual or potential conflicts of interest involving the individual and the Trust; and (viii) such other factors as the Board determines to be relevant in light of the existing composition of the Board.

Among the attributes or skills common to all Board members are their ability to review critically, evaluate, question and discuss information provided to them, to interact effectively with the other members of the Board, management, sub-advisers, other service providers, counsel and independent registered public accounting firms, and to exercise effective and independent business judgment in the performance of their duties as members of the Board. Each Board member's ability to perform his or her duties effectively has been attained through the Board member's business, consulting, public service and/or academic positions and through experience from service as a member of the Boards of the Eaton Vance family of funds ('Eaton Vance Fund Boards') (and/or in other capacities, including for any predecessor funds), public companies, or non-profit entities or other organizations as set forth below. Each Board member's ability to perform his or her duties effectively also has been enhanced by his or her educational background, professional training, and/or other life experiences.

In respect of each current member of the Board, the individual's substantial professional accomplishments and experience, including in fields related to the operations of registered investment companies, were a significant factor in the determination that the individual should serve as a member of the Board. The following is a summary of each Board member's particular professional experience and additional considerations that contributed to the Board's conclusion that he or she should serve as a member of the Board:

Eaton Vance National Municipal Opportunities Trust 18 SAI dated July 22, 2021

Thomas E. Faust Jr. Mr. Faust has served as a member of the Eaton Vance Fund Boards since 2007. Effective March 1, 2021, he is Chairman of MSIM. He is also a member of the Board of Managers and President of EV, Chief Executive Officer and President of Eaton Vance and BMR, and Director of EVD. Mr. Faust previously served as Chairman and Chief Executive Officer of EVC from 2007 through March 1, 2021 and as President of EVC from 2006 through March 1, 2021. Mr. Faust served as a Director of Hexavest Inc. from 2012-2021. From 2016 through 2019, Mr. Faust served as a Director of SigFig Wealth Management LLC. Mr. Faust previously served as an equity analyst, portfolio manager, Director of Equity Research and Management and Chief Investment Officer of Eaton Vance from 1985-2007. He holds B.S. degrees in Mechanical Engineering and Economics from the Massachusetts Institute of Technology and an MBA from Harvard Business School. Mr. Faust has been a Chartered Financial Analyst since 1988. He is a trustee and member of the executive committee of the Boston Symphony Orchestra, Inc. and trustee emeritus of Wellesley College.

Mark R. Fetting. Fetting has served as a member of the Eaton Vance Fund Boards since 2016 and is the Chairperson of the Contract Review Committee. He has over 30 years of experience in the investment management industry as an executive and in various leadership roles. From 2000 through 2012, Mr. Fetting served in several capacities at Legg Mason, Inc., including most recently serving as President, Chief Executive Officer, Director and Chairman from 2008 to his retirement in 2012. He also served as a Director/Trustee and Chairman of the Legg Mason family of funds from 2008-2012 and Director/Trustee of the Royce family of funds from 2001-2012. From 2001 through 2008, Mr. Fetting also served as President of the Legg Mason family of funds. From 1991 through 2000, Mr. Fetting served as Division President and Senior Officer of Prudential Financial Group, Inc. and related companies. Early in his professional career, Mr. Fetting was a Vice President at T. Rowe Price and served in leadership roles within the firm's mutual fund division from 1981-1987.

Cynthia E. Frost. Ms. Frost has served as a member of the Eaton Vance Fund Boards since 2014 and is the Chairperson of the Portfolio Management Committee. From 2000 through 2012, Ms. Frost was the Chief Investment Officer of Brown University, where she oversaw the evaluation, selection and monitoring of the third party investment managers who managed the university's endowment. From 1995 through 2000, Ms. Frost was a Portfolio Strategist for Duke Management Company, which oversaw Duke University's endowment. Ms. Frost also served in various investment and consulting roles at Cambridge Associates from 1989-1995, Bain and Company from 1987-1989 and BA Investment Management Company from 1983-1985. She serves as a member of the investment committee of The MCNC Endowment.

George J. Gorman. Mr. Gorman has served as a member of the Eaton Vance Fund Boards since 2014 and the Independent Chairperson of the Board. From 1974 through 2009, Mr. Gorman served in various capacities at Ernst & Young LLP, including as a Senior Partner in the Asset Management Group (from 1988) specializing in managing engagement teams responsible for auditing mutual funds registered with the SEC, hedge funds and private equity funds. Mr. Gorman also has experience serving as an independent trustee of other mutual fund complexes, including the Bank of America Money Market Funds Series Trust from 2011-2014 and the Ashmore Funds from 2010-2014.

Valerie A. Mosley. Ms. Mosley has served as a member of the Eaton Vance Fund Boards since 2014 and is the Chairperson of the Governance Committee. She currently owns and manages a consulting and investment firm, Valmo Ventures, and in 2020 founded Upward Wealth, Inc., doing business as BrightUP, a fintech platform focused on helping everyday workers grow their net worth and reinforce their self-worth. From 1992 through 2012, Ms. Mosley served in several capacities at Wellington Management Company, LLP, an investment management firm, including as a Partner, Senior Vice President, Portfolio Manager and Investment Strategist. Ms. Mosley also served as Chief Investment Officer at PG Corbin Asset Management from 1990-1992 and worked in institutional corporate bond sales at Kidder Peabody from 1986-1990. She was also a Director of Progress Investment Management Company, a manager of emerging managers until 2020. She is a Director of Groupon, Inc., an ecommerce provider, and a Director of Envestnet, Inc., a provider of intelligent systems for wealth management and financial wellness. She is also a Director of DraftKings, Inc., a digital sports entertainment and gaming company. Ms. Mosley previously served as a Director of Dynex Capital, Inc., a mortgage REIT, from 2013-2020. She serves as a trustee or board member of several major non-profit organizations and endowments, including New Profit, a social venture firm that identifies, invests in and helps scale social entrepreneurs. She is a member of the Risk Audit Committee of the United Auto Workers Retiree Medical Benefits Trust and a member of the Investment Advisory Committee of New York State Common Retirement Fund. Ms. Mosley serves on the Institutional Investors Advisory Council of MiDA, a U.S. Agency for International Development partner focused on investment opportunities in Africa and also advises Impact X and Zeal Capital, venture funds focused predominately on underrepresented entrepreneurs.

William H. Park. Mr. Park has served as a member of the Eaton Vance Fund Boards since 2003 and was formerly Independent Chairperson of the Board from 2016-2021. Mr. Park was formerly a consultant from 2012-2014 and formerly the Chief Financial Officer of Aveon Group, L.P. from 2010-2011. Mr. Park also served as Vice Chairman of Commercial Industrial Finance Corp. from 2006-2010, as President and Chief Executive Officer of Prizm Capital Management, LLC from 2002-2005, as Executive Vice President and Chief Financial Officer of United Asset Management Corporation from 1982-2001 and as Senior Manager of Price Waterhouse (now PricewaterhouseCoopers) from 1972-1981.

Eaton Vance National Municipal Opportunities Trust 19 SAI dated July 22, 2021

Helen Frame Peters. Dr. Peters has served as a member of the Eaton Vance Fund Boards since 2008. Dr. Peters is currently a Professor of Finance at Carroll School of Management, Boston College and was formerly Dean of Carroll School of Management from 2000-2002. Dr. Peters was previously a Director of BJ's Wholesale Club, Inc. from 2004-2011. In addition, Dr. Peters was the Chief Investment Officer, Fixed Income at Scudder Kemper Investments from 1998-1999 and Chief Investment Officer, Equity and Fixed Income at Colonial Management Associates from 1991-1998. Dr. Peters also served as a Trustee of SPDR Index Shares Funds and SPDR Series Trust from 2000-2009 and as a Director of the Federal Home Loan Bank of Boston from 2007-2009.

Keith Quinton. Mr. Quinton has served as a member of the Eaton Vance Fund Boards since October 1, 2018. He had over thirty years of experience in the investment industry before retiring from Fidelity Investments in 2014. Prior to joining Fidelity, Mr. Quinton was a vice president and quantitative analyst at MFS Investment Management from 2000-2001. From 1997 through 2000, he was a senior quantitative analyst at Santander Global Advisors and, from 1995 through 1997, Mr. Quinton was senior vice president in the quantitative equity research department at Putnam Investments. Prior to joining Putnam Investments, Mr. Quinton served in various investment roles at Eberstadt Fleming, Falconwood Securities Corporation and Drexel Burnham Lambert, where he began his career in the investment industry as a senior quantitative analyst in 1983. Mr. Quinton served as an Independent Investment Committee Member of the New Hampshire Retirement System, a five member committee that manages investments based on the investment policy and asset allocation approved by the board of trustees (2017-2021), and as a Director, (2016-2021) and Chairman, (2019-2021) of the New Hampshire Municipal Bond Bank.

Marcus L. Smith. Mr. Smith has served as a member of the Eaton Vance Fund Boards since October 1, 2018 and is the Chairperson of the Ad Hoc Committee for Closed-End Fund Matters. Mr. Smith has been a Director of First Industrial Realty Trust, Inc., a fully integrated owner, operator and developer of industrial real estate, since 2021, where he serves on the Investment and Nominating/Corporate Governance Committees. Since 2017, Mr. Smith has been a Director of MSCI Inc., a leading provider of investment decision support tools worldwide, where he serves on the Compensation and Talent Management Committee and Strategy & Finance Committee. From 2017 through 2018, he served as a Director of DCT Industrial Trust Inc., a leading logistics real estate company, where he served as a member of the Nominating and Corporate Governance and Audit Committees. From 1994 through 2017, Mr. Smith served in several capacities at MFS Investment Management, an investment management firm, where he managed the MFS Institutional International Fund for 17 years and the MFS Concentrated International Fund for 10 years. In addition to his portfolio management duties, Mr. Smith served as Director of Equity, Canada from 2012-2017, Director of Equity, Asia from 2010-2012, and Director of Asian Equity Research from 2005-2010. Prior to joining MFS, Mr. Smith was a senior consultant at Andersen Consulting (now known as Accenture) from 1988-1992. Mr. Smith served as a United States Army Reserve Officer from 1987-1992. He was also a trustee of the University of Mount Union from 2008-2020 and served on the Boston advisory board of the Posse Foundation from 2015-2021. Mr. Smith currently sits on the Harvard Medical School Advisory Council on Education, the Board of Directors for Facing History and Ourselves and is a Trustee of the Core Knowledge Foundation.

Susan J. Sutherland. Ms. Sutherland has served as a member of the Eaton Vance Fund Boards since 2015 and is the Chairperson of the Compliance Reports and Regulatory Matters Committee. She is also a Director of Ascot Group Limited and certain of its subsidiaries. Ascot Group Limited, through its related businesses including Syndicate 1414 at Lloyd's of London, is a leading global underwriter of specialty property and casualty insurance and reinsurance. In addition, Ms. Sutherland is a Director of Kairos Acquisition Corp., which is concentrating on acquisition and business combination efforts within the insurance and insurance technology (also known as 'InsurTech') sectors. Ms. Sutherland was a Director of Montpelier Re Holdings Ltd., a global provider of customized reinsurance and insurance products, from 2013 until its sale in 2015 and of Hagerty Holding Corp., a leading provider of specialized automobile and marine insurance from 2015-2018. From 1982 through 2013, Ms. Sutherland was an associate, counsel and then a partner in the Financial Institutions Group of Skadden, Arps, Slate, Meagher & Flom LLP, where she primarily represented U.S. and international insurance and reinsurance companies, investment banks and private equity firms in insurance-related corporate transactions. In addition, Ms. Sutherland is qualified as a Governance Fellow of the National Association of Corporate Directors and has also served as a board member of prominent non-profit organizations.

Scott E. Wennerholm. Mr. Wennerholm has served as a member of the Eaton Vance Fund Boards since 2016 and is the Chairperson of the Audit Committee. He has over 30 years of experience in the financial services industry in various leadership and executive roles. Mr. Wennerholm served as Chief Operating Officer and Executive Vice President at BNY Mellon Asset Management from 2005-2011. He also served as Chief Operating Officer and Chief Financial Officer at Natixis Global Asset Management from 1997-2004 and was a Vice President at Fidelity Investments Institutional Services from 1994-1997. In addition, Mr. Wennerholm served as a Trustee at Wheelock College, a postsecondary institution from 2012-2018.

Eaton Vance National Municipal Opportunities Trust 20 SAI dated July 22, 2021

The Board(s) of the Trust has several standing Committees, including the Governance Committee, the Audit Committee, the Portfolio Management Committee, the Compliance Reports and Regulatory Matters Committee, the Contract Review Committee and the Ad Hoc Committee for Closed-End Fund Matters. Each of the Committees are comprised of only noninterested Trustees.

Mmes. Mosley (Chairperson), Frost, Peters and Sutherland, and Messrs. Fetting, Gorman, Park, Quinton, Smith and Wennerholm are members of the Governance Committee. The purpose of the Governance Committee is to consider, evaluate and make recommendations to the Board with respect to the structure, membership and operation of the Board and the Committees thereof, including the nomination and selection of noninterested Trustees and a Chairperson of the Board and the compensation of such persons. During the fiscal year ended March 31, 2021, the Governance Committee convened six times.

The Governance Committee will, when a vacancy exists, consider a nominee for Trustee recommended by a shareholder, provided that such recommendation is submitted in writing to the Trust's Secretary at the principal executive office of the Trust. Such recommendations must be accompanied by biographical and occupational data on the candidate (including whether the candidate would be an 'interested person' of the Trust), a written consent by the candidate to be named as a nominee and to serve as Trustee if elected, record and ownership information for the recommending shareholder with respect to the Trust, and a description of any arrangements or understandings regarding recommendation of the candidate for consideration.

Messrs. Wennerholm (Chairperson), Gorman and Park and Ms. Peters are members of the Audit Committee. The Board has designated Messrs. Gorman, Park and Wennerholm, each a noninterested Trustee, as audit committee financial experts. The Audit Committee's purposes are to (i) oversee the Trust's accounting and financial reporting processes, its internal control over financial reporting, and, as appropriate, the internal control over financial reporting of certain service providers; (ii) oversee or, as appropriate, assist Board oversight of the quality and integrity of the Trust's financial statements and the independent audit thereof; (iii) oversee, or, as appropriate, assist Board oversight of, the Trust's compliance with legal and regulatory requirements that relate to the Trust's accounting and financial reporting, internal control over financial reporting and independent audits; (iv) approve prior to appointment the engagement and, when appropriate, replacement of the independent registered public accounting firm, and, if applicable, nominate the independent registered public accounting firm to be proposed for shareholder ratification in any proxy statement of the Trust; (v) evaluate the qualifications, independence and performance of the independent registered public accounting firm and the audit partner in charge of leading the audit; and (vi) prepare, as necessary, audit committee reports consistent with the requirements of applicable SEC and stock exchange rules for inclusion in the proxy statement of the Trust. During the fiscal year ended March 31, 2021, the Audit Committee convened eleven times.

Messrs. Fetting (Chairperson), Gorman, Park, Quinton, Smith and Wennerholm, and Mmes. Frost, Mosley, Peters and Sutherland are members of the Contract Review Committee. The purposes of the Contract Review Committee are to consider, evaluate and make recommendations to the Board concerning the following matters: (i) contractual arrangements with each service provider to the Trust, including advisory, sub-advisory, transfer agency, custodial and fund accounting, distribution services and administrative services; (ii) any and all other matters in which any service provider (including Eaton Vance or any affiliated entity thereof) has an actual or potential conflict of interest with the interests of the Trust; and (iii) any other matter appropriate for review by the noninterested Trustees, unless the matter is within the responsibilities of the other Committees of the Board. During the fiscal year ended March 31, 2021, the Contract Review Committee convened ten times.

Mmes. Frost (Chairperson), Mosley and Peters and Messrs. Smith and Wennerholm are members of the Portfolio Management Committee. The purposes of the Portfolio Management Committee are to: (i) assist the Board in its oversight of the portfolio management process employed by the Trust and its investment adviser and sub-adviser(s), if applicable, relative to the Trust's stated objective(s), strategies and restrictions; (ii) assist the Board in its oversight of the trading policies and procedures and risk management techniques applicable to the Trust; and (iii) assist the Board in its monitoring of the performance results of all funds and portfolios, giving special attention to the performance of certain funds and portfolios that it or the Board identifies from time to time. During the fiscal year ended March 31, 2021, the Portfolio Management Committee convened seven times.

Ms. Sutherland (Chairperson) and Messrs. Fetting, Gorman and Quinton are members of the Compliance Reports and Regulatory Matters Committee. The purposes of the Compliance Reports and Regulatory Matters Committee are to: (i) assist the Board in its oversight role with respect to compliance issues and certain other regulatory matters affecting the Trust; (ii) serve as a liaison between the Board and the Trust's CCO; and (iii) serve as a 'qualified legal compliance committee' within the rules promulgated by the SEC. During the fiscal year ended March 31, 2021, the Compliance Reports and Regulatory Matters Committee convened seven times.

Messrs. Fetting (Chairperson), Gorman and Smith are members of the Ad Hoc Committee for Closed-End Fund Matters. The purpose of the Ad Hoc Committee for Closed-End Fund Matters is to consider, evaluate and make recommendations to the Board with respect to issues specifically related to Eaton Vance Closed-End Funds. During the fiscal year ended March 31, 2021, the Ad Hoc Committee for Closed-End Fund Matters convened five times.

Eaton Vance National Municipal Opportunities Trust 21 SAI dated July 22, 2021

Share Ownership. The following table shows the dollar range of equity securities beneficially owned by each Trustee in the Trust and in the Eaton Vance family of funds overseen by the Trustee as of December 31, 2020.

Name of Trustee Dollar Range of Equity Securities
Beneficially Owned in the Trust
Aggregate Dollar Range of Equity
Securities Beneficially Owned in Funds
Overseen by Trustee in the
Eaton Vance Family of Funds
Interested Trustee
Thomas E. Faust Jr. None Over $100,000
Noninterested Trustees
Mark R. Fetting None Over $100,000
Cynthia E. Frost None Over $100,000
George J. Gorman None Over $100,000
Valerie A. Mosley None Over $100,000
William H. Park None Over $100,000
Helen Frame Peters None Over $100,000
Keith Quinton None Over $100,000
Marcus L. Smith None Over $100,000
Susan J. Sutherland None Over $100,000(1)
Scott E. Wennerholm None Over $100,000(1)
(1) Includes shares which may be deemed to be beneficially owned through the Trustee Deferred Compensation Plan.

As of December 31, 2020, no noninterested Trustee or any of their immediate family members owned beneficially or of record any class of securities of EVC, EVD, any sub-adviser, if applicable, or any person controlling, controlled by or under common control with EVC or EVD or any sub-adviser, if applicable, collectively ('Affiliated Entity').

During the calendar years ended December 31, 2019 and December 31, 2020, no noninterested Trustee (or their immediate family members) had:

(1) Any direct or indirect interest in any Affiliated Entity;
(2) Any direct or indirect material interest in any transaction or series of similar transactions with (i) the Trust; (ii) another fund managed or distributed by any Affiliated Entity; (iii) any Affiliated Entity; or (iv) an officer of any of the above; or
(3) Any direct or indirect relationship with (i) the Trust; (ii) another fund managed or distributed by any Affiliated Entity; (iii) any Affiliated Entity; or (iv) an officer of any of the above.

During the calendar years ended December 31, 2019 and December 31, 2020, no officer of any Affiliated Entity served on the Board of Directors of a company where a noninterested Trustee of the Trust or any of their immediate family members served as an officer.

Noninterested Trustees may elect to defer receipt of all or a percentage of their annual fees in accordance with the terms of a Trustees Deferred Compensation Plan (the 'Deferred Compensation Plan'). Under the Deferred Compensation Plan, an eligible Board member may elect to have all or a portion of his or her deferred fees invested in the shares of one or more funds in the Eaton Vance family of funds, and the amount paid to the Board members under the Deferred Compensation Plan will be determined based upon the performance of such investments. Deferral of Board members' fees in accordance with the Deferred Compensation Plan will have a negligible effect on the assets, liabilities, and net income of a participating fund or portfolio, and do not require that a participating Board member be retained. There is no retirement plan for Board members.

Eaton Vance National Municipal Opportunities Trust 22 SAI dated July 22, 2021

The fees and expenses of the Trustees of the Trust are paid by the Trust. A Board member who is a member of the Eaton Vance organization receives no compensation from the Trust. During the fiscal year ended March 31, 2021, the Trustees of the Trust earned the following compensation in their capacities as Board members from the Trust. For the year ended December 31, 2020, the Board members earned the following compensation in their capacities as members of the Eaton Vance Fund Boards(1):

Source of Compensation Mark R.
Fetting
Cynthia E.
Frost
George J.
Gorman
Valerie A.
Mosley
William H
Park
Helen Frame
Peters
Keith
Quinton
Marcus L.
Smith
Susan J.
Sutherland
Scott E.
Wennerholm
Trust $1,713 $1,834 $1,907 $1,834(2) $2,321 $1,737 $1,663 $1,664 $1,858(3) $1,907
Trust and Fund
Complex(1)
$ 348,306 $ 373,305 $ 387,056 $ 378,709(4) $ 470,806 $ 351,652 $ 338,306 $ 338,306 $ 373,305(5) $ 387,056
(1) As of July 22, 2021, the Eaton Vance fund complex consists of 139 registered investment companies or series thereof.
(2) Includes $594 of deferred compensation.
(3) Includes $1,858 of deferred compensation.

(4) Includes $20,000 of deferred compensation.

(5) Includes $ 370,208 of deferred compensation.

Proxy Voting Policy. The Board adopted a proxy voting policy and procedures (the 'Trust Policy'), pursuant to which the Board has delegated proxy voting responsibility to the Adviser and adopted the Adviser's proxy voting policies and procedures (the 'Adviser Policies'). An independent proxy voting service has been retained to assist in the voting of Trust proxies through the provision of vote analysis, implementation and recordkeeping and disclosure services. The members of the Board will review the Trust's proxy voting records from time to time and will review annually the Adviser Policies. For a copy of the Trust Policy and the Adviser Policies, see Appendix B and C, respectively. Pursuant to certain provisions of the 1940 Act and certain exemptive orders relating to funds investing in other funds, a Trust may be required or may elect to vote its interest in another fund in the same proportion as the holders of all other shares of that fund. Information on how the Trust voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is available (1) without charge, upon request, by calling 1-800-262-1122, and (2) on the SEC's website at http://www.sec.gov.

INVESTMENT ADVISORY AND OTHER SERVICES

Eaton Vance, its affiliates and its predecessor companies have been managing assets of individuals and institutions since 1924 and of investment companies since 1931. Eaton Vance and its affiliates act as adviser to a family of mutual funds, and individual and various institutional accounts, including corporations, hospitals, retirement plans, universities, foundations and trusts.

As described in the Prospectus, upon the closing of the transaction by which Morgan Stanley acquired EVC (the 'Transaction'), the Trust entered into a new investment advisory and administrative agreement with Eaton Vance. The Trust will be responsible for all of its costs and expenses not expressly stated to be payable by Eaton Vance under the Investment Advisory and Administrative Agreement (the 'Advisory Agreement'). Effective March 1, 2021, any fee reduction agreement previously applicable to the Trust was incorporated into its new investment advisory agreement with Eaton Vance.

The Advisory Agreement with the Adviser continues in effect through and including the second anniversary of its execution and shall continue in full force and effect indefinitely thereafter, but only so long as such continuance after such second anniversary is specifically approved at least annually (i) by the vote of a majority of those Trustees of the Trust who are not interested persons of the Adviser or the Trust cast at a meeting specifically called for the purpose of voting on such approval pursuant to the requirements of the 1940 Act and (ii) by the Trust's Board or by vote of a majority of the outstanding voting securities of the Trust. The Agreement may be terminated at any time without penalty on sixty (60) days' written notice by either party, or by vote of the majority of the outstanding voting securities of the Trust, and will terminate automatically in the event of its assignment. The Agreement provides that the investment adviser may render services to others. The Agreement also provides that Eaton Vance shall not be liable for any loss incurred in connection with the performance of its duties, or action taken or omitted under the Agreements, in the absence of willful misfeasance, bad faith, gross negligence or reckless disregard of its obligations and duties thereunder, and Eaton Vance shall not be liable for any losses sustained in the acquisition, holding or disposition of any security or other investment. The Agreement is not intended to, and does not, confer upon any person not a party to it any right, benefit or remedy of any nature.

Eaton Vance National Municipal Opportunities Trust 23 SAI dated July 22, 2021

Pursuant to the Advisory Agreement, the Trust has agreed to pay the Adviser as compensation a fee for investment advisory services in the amount of 0.60% of the Trust's average daily gross assets up to and including $1.5 billion, and 0.59% of the Trust's average daily gross assets in excess of $1.5 billion. For purposes of this calculation, 'gross assets' of the Trust shall mean total assets of the Trust, including any form of investment leverage, minus all accrued expenses incurred in the normal course of operations, but not excluding any liabilities or obligations attributable to investment leverage obtained through (i) indebtedness of any type (including, without limitation, borrowing through a credit facility or the issuance of debt securities or through the purchase of residual interest bonds), (ii) the issuance of preferred stock or other similar preference securities, (iii) the reinvestment of collateral received for securities loaned in accordance with the Trust's investment objectives and policies, and/or (iv) any other means; all as determined in accordance with generally accepted accounting principles.

For the fiscal years ended March 31, 2021, March 31, 2020 and March 31, 2019, the Trust incurred $2,080,827, $2,129,428 and $2,118,237, respectively, in investment adviser and administration fees.

Information About Eaton Vance.  Eaton Vance is a business trust organized under the laws of The Commonwealth of Massachusetts. EV serves as trustee of Eaton Vance. As described in the Prospectus, following the closing of the Transaction on March 1, 2021, EV and Eaton Vance became indirect wholly owned subsidiaries of Morgan Stanley (NYSE: MS), a preeminent global financial services firm engaged in securities trading and brokerage activities, as well as providing investment banking, research and analysis, financing and financial advisory services.

Prior to March 1, 2021, each of EV and Eaton Vance were wholly owned subsidiaries of EVC, a Maryland corporation and publicly-held holding company, and BMR was an indirect wholly owned subsidiary of EVC. EVC, through its subsidiaries and affiliates, engaged primarily in investment management, administration and marketing activities. The Directors of EVC were Thomas E. Faust Jr., Ann E. Berman, Leo I. Higdon, Jr., Paula A. Johnson, Brian D. Langstraat, Dorothy E. Puhy, Winthrop H. Smith, Jr. and Richard A. Spillane, Jr. All shares of the outstanding Voting Common Stock of EVC were deposited in a Voting Trust, the Voting Trustees of which were Mr. Faust, Paul W. Bouchey, Craig R. Brandon, Daniel C. Cataldo, Michael A. Cirami, Cynthia J. Clemson, James H. Evans, Maureen A. Gemma, Laurie G. Hylton, Mr. Langstraat, Thomas Lee, Frederick S. Marius, David C. McCabe, Edward J. Perkin, Lewis R. Piantedosi, Charles B. Reed, Craig P. Russ, Thomas C. Seto, John L. Shea, Eric A. Stein, John H. Streur, Andrew N. Sveen, Payson F. Swaffield, R. Kelly Williams and Matthew J. Witkos (all of whom are or were officers of Eaton Vance or its affiliates). The Voting Trustees had unrestricted voting rights for the election of Directors of EVC. Prior to March 1, 2021, all of the outstanding voting trust receipts issued under said Voting Trust were owned by certain of the officers of BMR and Eaton Vance who may also have been officers, or officers and Directors of EVC and EV. As indicated under 'Trustees and Officers,' all of the officers of the Trust (as well as Mr. Faust who is also a Trustee) are employees of Eaton Vance.

Code of Ethics. The Adviser and the Trust have adopted codes of ethics (the 'Codes of Ethics') governing personal securities transactions pursuant to Rule 17j-1 under the 1940 Act. Under the Codes of Ethics, employees of the Adviser may purchase and sell securities (including securities held or eligible for purchase by the Trust) subject to the provisions of the Codes of Ethics and certain employees are also subject to pre-clearance, reporting requirements and/or other procedures.

The Codes of Ethics can be reviewed on the EDGAR Database on the SEC's Internet site (http://www.sec.gov), or a copy of the Codes of Ethics may be requested by electronic mail at [email protected]

Portfolio Managers. Cynthia J. Clemson serves as the portfolio manager of the Trust. The following table shows, as of the Trust's most recent fiscal year end, the number of accounts Ms. Clemson managed in each of the listed categories and the total assets (in millions of dollars) in the accounts managed within each category. The table also shows the number of accounts with respect to which the advisory fee is based on the performance of the account, if any, and the total assets (in millions of dollars) in those accounts.

Number of
All Accounts
Total Assets of
All Accounts
Number of Accounts
Paying a Performance Fee
Total Assets of Accounts
Paying a Performance Fee
Registered Investment Companies 10 $4,567.7 0 $0
Other Pooled Investment Vehicles 0 $0 0 $0
Other Accounts 3 $240.8 0 $0

Ms. Clemson did not beneficially own shares of the Trust as of March 31, 2021. As of December 31, 2020, Ms. Clemson beneficially owned over $1,000,000 of funds in the Eaton Vance Fund Complex.

It is possible that conflicts of interest may arise in connection with a portfolio manager's management of Trust's investments on the one hand and the investments of other accounts for which a portfolio manager is responsible on the other. For example, a portfolio manager may have conflicts of interest in allocating management time, resources and investment opportunities among Trust and other accounts she advises. In addition, due to differences in the investment strategies or restrictions between Trust and the other accounts, the portfolio manager may take action with respect to another account that differs from the action taken with respect to Trust. In some cases, another account

Eaton Vance National Municipal Opportunities Trust 24 SAI dated July 22, 2021

managed by a portfolio manager may compensate the investment adviser based on the performance of the securities held by that account. The existence of such a performance based fee may create additional conflicts of interest for the portfolio manager in the allocation of management time, resources and investment opportunities. Whenever conflicts of interest arise, the portfolio manager will endeavor to exercise her discretion in a manner that she believes is equitable to all interested persons. The investment adviser has adopted several policies and procedures designed to address these potential conflicts including a code of ethics and policies that govern the investment adviser's trading practices, including among other things the aggregation and allocation of trades among clients, brokerage allocations, cross trades and best execution.

Compensation Structure for Eaton Vance. Compensation of the Adviser's portfolio managers and other investment professionals has the following primary components: (1) a base salary, (2) an annual cash bonus, and (3) annual non-cash compensation consisting of restricted shares of Morgan Stanley stock that are subject to a fixed vesting and distribution schedule. The Adviser's investment professionals also receive certain retirement, insurance and other benefits that are broadly available to the Adviser's employees. Compensation of the Adviser's investment professionals is reviewed primarily on an annual basis. Cash bonuses, stock-based compensation awards, and adjustments in base salary are typically paid or put into effect at or shortly after the December 31st fiscal year end of Morgan Stanley.

Method to Determine Compensation. The investment adviser compensates its portfolio managers based primarily on the scale and complexity of their portfolio responsibilities and the total return performance of managed funds and accounts versus the benchmark(s) stated in the prospectus, as well as an appropriate peer group (as described below). In addition to rankings within peer groups of funds on the basis of absolute performance, consideration may also be given to relative risk-adjusted performance. Risk-adjusted performance measures include, but are not limited to, the Sharpe ratio, which uses standard deviation and excess return to determine reward per unit of risk. Performance is normally based on periods ending on the September 30th preceding fiscal year end. Fund performance is normally evaluated primarily versus peer groups of funds as determined by Lipper Inc. and/or Morningstar, Inc. When a fund's peer group as determined by Lipper or Morningstar is deemed by the investment adviser's management not to provide a fair comparison, performance may instead be evaluated primarily against a custom peer group or market index. In evaluating the performance of a fund and its manager, primary emphasis is normally placed on three-year performance, with secondary consideration of performance over longer and shorter periods. For funds that are tax-managed or otherwise have an objective of after-tax returns, performance is measured net of taxes. For other funds, performance is evaluated on a pre-tax basis. For funds with an investment objective other than total return (such as current income), consideration will also be given to the fund's success in achieving its objective. For managers responsible for multiple funds and accounts, investment performance is evaluated on an aggregate basis, based on averages or weighted averages among managed funds and accounts. Funds and accounts that have performance-based advisory fees are not accorded disproportionate weightings in measuring aggregate portfolio manager performance.

The compensation of portfolio managers with other job responsibilities (such as heading an investment group or providing analytical support to other portfolios) will include consideration of the scope of such responsibilities and the managers' performance in meeting them.

The investment adviser seeks to compensate portfolio managers commensurate with their responsibilities and performance, and competitive with other firms within the investment management industry. The investment adviser participates in investment-industry compensation surveys and utilizes survey data as a factor in determining salary, bonus and stock-based compensation levels for portfolio managers and other investment professionals. Salaries, bonuses and stock-based compensation are also influenced by the operating performance of the investment adviser and Morgan Stanley. The overall annual cash bonus pool is generally based on a substantially fixed percentage of pre-bonus adjusted operating income. While the salaries of the investment adviser's portfolio managers are comparatively fixed, cash bonuses and stock-based compensation may fluctuate significantly from year to year, based on changes in manager performance and other factors as described herein. For a high performing portfolio manager, cash bonuses and stock-based compensation may represent a substantial portion of total compensation.

Investment Advisory Services. Under the general supervision of the Trust's Board, Eaton Vance will carry out the investment and reinvestment of the assets of the Trust, will furnish continuously an investment program with respect to the Trust, will determine which securities should be purchased, sold or exchanged, and will implement such determinations. Eaton Vance will furnish to the Trust investment advice and provide related office facilities and personnel for servicing the investments of the Trust. Eaton Vance will compensate all Trustees and officers of the Trust who are members of the Eaton Vance organization and who render investment services to the Trust, and will also compensate all other Eaton Vance personnel who provide research and investment services to the Trust.

Eaton Vance National Municipal Opportunities Trust 25 SAI dated July 22, 2021

Commodity Futures Trading Commission Registration. The Commodity Futures Trading Commission ('CFTC') has adopted regulations that subject registered investment companies and advisers to regulation by the CFTC if a fund invests more than a prescribed level of its assets in certain CFTC-regulated instruments (including futures, certain options and swaps agreements) or markets itself as providing investment exposure to such instruments. The Adviser has claimed an exclusion from the definition of the term 'commodity pool operator' under the Commodity Exchange Act with respect to its management of the Trust. Accordingly, neither the Trust nor the Adviser with respect to the operation of the Trust is subject to CFTC regulation. Because of its management of other strategies, Eaton Vance is registered with the CFTC as a commodity pool operator. Eaton Vance is also registered as a commodity trading advisor. The CFTC has neither reviewed nor approved the Trust's investment strategies or this SAI.

Administrative Services. Under the Advisory Agreement, Eaton Vance has been engaged to administer the Trust's affairs, subject to the supervision of the Board, and shall furnish office space and all necessary office facilities, equipment and personnel for administering the affairs of the Trust.

DETERMINATION OF NET ASSET VALUE

The net asset value of the Trust is determined by State Street Bank and Trust Company (as agent and custodian) by subtracting the liabilities of the Trust from the value of its total assets. The Trust is closed for business and will not issue a net asset value on the following business holidays and any other business day that the New York Stock Exchange (the 'Exchange') is closed: New Year's Day, Martin Luther King, Jr. Day, Presidents' Day, Good Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving Day and Christmas Day.

The Board has approved procedures pursuant to which investments are valued for purposes of determining the Trust's net asset value. Listed below is a summary of the methods generally used to value investments (some or all of which may be held by the Trust) under the procedures.

· Equity securities (including common stock, exchange-traded funds, closed-end funds, preferred equity securities, exchange-traded notes and other instruments that trade on recognized stock exchanges) are valued at the last sale, official close or, if there are no reported sales, at the mean between the bid and asked price on the primary exchange on which they are traded.
· Most debt obligations are valued on the basis of market valuations furnished by a pricing service or at the mean of the bid and asked prices provided by recognized broker/dealers of such securities. The pricing service may use a pricing matrix to determine valuation.
· Short-term instruments with remaining maturities of less than 397 days are valued on the basis of market valuations furnished by a pricing service or based on dealer quotations.
· Foreign securities and currencies are valued in U.S. dollars based on foreign currency exchange quotations supplied by a pricing service.
· Senior and Junior Loans are valued on the basis of prices furnished by a pricing service. The pricing service uses transactions and market quotations from brokers in determining values.
· Futures contracts are valued at the settlement or closing price on the primary exchange or board of trade on which they are traded.
· Exchange-traded options are valued at the mean of the bid and asked prices. Over-the-counter options are valued based on quotations obtained from a pricing service or from a broker (typically the counterparty to the option).
· Non-exchange traded derivatives (including swap agreements, forward contracts and equity participation notes) are generally valued on the basis of valuations provided by a pricing service or using quotes provided by a broker/dealer (typically the counterparty) or, for total return swaps, based on market index data.
· Precious metals are valued at the New York Composite mean quotation.
· Liabilities with a payment or maturity date of 364 days or less are stated at their principal value and longer dated liabilities generally will be carried at their fair value.
· Valuations of foreign equity securities and total return swaps and exchange-traded futures contracts on non-North American equity indices are generally based on fair valuation provided by a pricing service.

Investments which are unable to be valued in accordance with the foregoing methodologies are valued at fair value using methods determined in good faith by or at the direction of the members of the Board. Such methods may include consideration of relevant factors, including but not limited to (i) the type of security and, the existence of any contractual restrictions on the security's disposition; (ii) the price and extent of public trading in similar securities of the issuer or of comparable companies or entities; (iii) quotations or relevant information obtained from broker-dealers or other market participants; (iv) information obtained from the issuer, analysts, and/or the appropriate stock exchange (for exchange-traded securities); (v) an analysis of the company's or entity's financial statements; (vi) an evaluation of the forces that influence the issuer and the market(s) in which the security is purchased and sold; (vii) any transaction involving the issuer of such securities; and (viii) any other factors deemed relevant by the investment adviser. For purposes of fair

Eaton Vance National Municipal Opportunities Trust 26 SAI dated July 22, 2021

valuation, the portfolio managers of one Eaton Vance fund that invests in Senior and Junior Loans may not possess the same information about a Senior or Junior Loan as the portfolio managers of another Eaton Vance fund. As such, at times the fair value of a Loan determined by certain Eaton Vance portfolio managers may vary from the fair value of the same Loan determined by other portfolio managers.

The Trust may invest in Eaton Vance Cash Reserves Fund, LLC (Cash Reserves Fund), an affiliated investment company managed by Eaton Vance. Cash Reserves Fund generally values its investment securities utilizing the amortized cost valuation technique in accordance with Rule 2a-7 under the 1940 Act. This technique involves initially valuing a portfolio security at its cost and thereafter assuming a constant amortization to maturity of any discount or premium. If amortized cost is determined not to approximate fair value, Cash Reserves Fund may value its investment securities in the same manner as debt obligations described above.

PORTFOLIO TRADING

Decisions concerning the execution of portfolio security transactions, including the selection of the market and the broker-dealer firm or other financial intermediary (each an 'intermediary'), are made by the investment adviser. The Trust is responsible for the expenses associated with its portfolio transactions. The investment adviser is also responsible for the execution of transactions for all other accounts managed by it. The investment adviser places the portfolio security transactions for execution with one or more intermediaries. The investment adviser uses its best efforts to obtain execution of portfolio security transactions at prices that, in the investment adviser's judgment, are advantageous to the client and at a reasonably competitive spread or (when a disclosed commission is being charged) at reasonably competitive commission rates. In seeking such execution, the investment adviser will use its best judgment in evaluating the terms of a transaction, and will give consideration to various relevant factors, which may include, without limitation, the full range and quality of the intermediary's services, responsiveness of the intermediary to the investment adviser, the size and type of the transaction, the nature and character of the market for the security, the confidentiality, speed and certainty of effective execution required for the transaction, the general execution and operational capabilities of the intermediary the reputation, reliability, experience and financial condition of the intermediary, the value and quality of the services rendered by the intermediary in this and other transactions, and the amount of the spread or commission, if any. In addition, the investment adviser may consider the receipt of Research Services (as defined below), provided it does not compromise the investment adviser's obligation to seek best overall execution for the Trust and is otherwise in compliance with applicable law. The investment adviser may engage in portfolio transactions with an intermediary that sells shares of Eaton Vance funds, provided such transactions are not directed to that intermediary as compensation for the promotion or sale of such shares.

As described in the Prospectus, following the closing of the Transaction on March 1, 2021, the investment adviser became an 'affiliated person,' as defined in the 1940 Act, of Morgan Stanley and its affiliates, including certain intermediaries (as previously defined). As a result, the investment adviser is subject to certain restrictions regarding transactions with Morgan Stanley-affiliated intermediaries, as set forth in the 1940 Act. Under certain circumstances, such restrictions may limit the investment adviser's ability to place portfolio transactions on behalf of a Fund or Trust at the desired time or price. Any transaction the investment adviser enters into with a Morgan Stanley-affiliated intermediary on behalf of a Fund or Trust will be done in compliance with applicable laws, rules, and regulations; will be subject to any restrictions contained in a Fund or Trust's investment advisory agreement; will be subject to the investment adviser's duty to seek best execution; and will comply with any applicable policies and procedures of the investment adviser, as described below.

Subject to the overriding objective of obtaining the best execution of orders and applicable rules and regulations, as described above, a Fund or Trust may use an affiliated intermediary, including a Morgan Stanley-affiliated intermediary, to effect Fund or Trust portfolio transactions, including transactions in futures contracts and options on futures contracts, under procedures adopted by the Board. In order to use such affiliated intermediaries, the Trust's Board must approve and periodically review procedures reasonably designed to ensure that commission rates and other remuneration paid to the affiliated intermediaries are fair and reasonable in comparison to those of other intermediaries for comparable transactions involving similar securities being purchased or sold during a comparable time period.

Pursuant to an order issued by the SEC, a Fund or Trust is permitted to engage in principal transactions in money market instruments, subject to certain conditions, with Morgan Stanley & Co. LLC, a broker-dealer affiliated with Morgan Stanley.

Municipal obligations, including state obligations, purchased and sold by the Trust are generally traded in the over-the-counter market on a net basis (i.e., without commission) through intermediaries acting for their own account rather than as brokers, or otherwise involve transactions directly with the issuer of such obligations. Such intermediaries attempt to profit from such transactions by buying at the bid price and selling at the higher asked price of the market for such obligations, and the difference between the bid and asked price is customarily referred to as the spread. The Trust may also purchase municipal obligations from underwriters, and dealers in fixed-price offerings, the cost of which may include undisclosed fees and concessions to the underwriters. On occasion it may be necessary or appropriate to purchase or sell a security

Eaton Vance National Municipal Opportunities Trust 27 SAI dated July 22, 2021

through a broker on an agency basis, in which case the Trust will incur a brokerage commission. Although spreads or commissions on portfolio security transactions will, in the judgment of the investment adviser, be reasonable in relation to the value of the services provided, spreads or commissions exceeding those which another firm might charge may be paid to intermediaries who were selected to execute transactions on behalf of the Trust and the investment adviser's other clients for providing brokerage and research services to the investment adviser as permitted by applicable law.

Pursuant to the safe harbor provided in Section 28(e) of the Securities Exchange Act of 1934, as amended ('Section 28(e)') and to the extent permitted by other applicable law, a broker or dealer who executes a portfolio transaction may receive a commission that is in excess of the amount of commission another broker or dealer would have charged for effecting that transaction if the investment adviser determines in good faith that such compensation was reasonable in relation to the value of the brokerage and research services provided. This determination may be made on the basis of either that particular transaction or on the basis of the overall responsibility which the investment adviser and its affiliates have for accounts over which they exercise investment discretion. 'Research Services' as used herein includes any and all brokerage and research services to the extent permitted by Section 28(e) and other applicable law. Generally, Research Services may include, but are not limited to, such matters as research, analytical and quotation services, data, information and other services products and materials which assist the investment adviser in the performance of its investment responsibilities. More specifically, Research Services may include general economic, political, business and market information, industry and company reviews, evaluations of securities and portfolio strategies and transactions, technical analysis of various aspects of the securities markets, recommendations as to the purchase and sale of securities and other portfolio transactions, certain financial, industry and trade publications, certain news and information services and certain research oriented computer software, data bases and services. Any particular Research Service obtained through a broker-dealer may be used by the investment adviser in connection with client accounts other than those accounts which pay commissions to such broker-dealer, to the extent permitted by applicable law. Any such Research Service may be broadly useful and of value to the investment adviser in rendering investment advisory services to all or a significant portion of its clients, or may be relevant and useful for the management of only one client's account or of a few clients' accounts, or may be useful for the management of merely a segment of certain clients' accounts, regardless of whether any such account or accounts paid commissions to the broker-dealer through which such Research Service was obtained. The investment adviser evaluates the nature and quality of the various Research Services obtained through broker-dealer firms and, to the extent permitted by applicable law, may attempt to allocate sufficient portfolio security transactions to such firms to ensure the continued receipt of Research Services which the investment adviser believes are useful or of value to it in rendering investment advisory services to its clients. The investment adviser may also receive brokerage and Research Services from underwriters and dealers in fixedprice offerings, when permitted under applicable law.

Research Services provided by (and produced by) broker-dealers that execute portfolio transactions or from affiliates of executing broker-dealers are referred to as 'Proprietary Research.' Except for trades executed in jurisdictions where such consideration is not permissible, the investment adviser may and does consider the receipt of Proprietary Research Services as a factor in selecting broker dealers to execute client portfolio transactions, provided it does not compromise the investment adviser's obligation to seek best overall execution. In jurisdictions where permissible, the investment adviser also may consider the receipt of Research Services under so called 'client commission arrangements' or 'commission sharing arrangements' (both referred to as 'CCAs') as a factor in selecting broker dealers to execute transactions, provided it does not compromise the investment adviser's obligation to seek best overall execution. Under a CCA arrangement, the investment adviser may cause client accounts to effect transactions through a broker-dealer and request that the broker-dealer allocate a portion of the commissions paid on those transactions to a pool of commission credits that are paid to other firms that provide Research Services to the investment adviser. Under a CCA, the broker-dealer that provides the Research Services need not execute the trade. Participating in CCAs may enable the investment adviser to consolidate payments for research using accumulated client commission credits from transactions executed through a particular broker-dealer to periodically pay for Research Services obtained from and provided by other firms, including other broker-dealers that supply Research Services. The investment adviser believes that CCAs offer the potential to optimize the execution of trades and the acquisition of a variety of high quality Research Services that the investment adviser might not be provided access to absent CCAs. The investment adviser may enter into CCA arrangements with a number of broker-dealers and other firms, including certain affiliates of the investment adviser. The investment adviser will only enter into and utilize CCAs to the extent permitted by Section 28(e) and other applicable law.

Fund or Trust trades executed by an affiliate of the investment adviser licensed in the United Kingdom may implicate laws of the United Kingdom, including rules of the UK Financial Conduct Authority, which govern client trading commissions and Research Services ('UK Law'). Broadly speaking, under UK Law the investment adviser may not accept any good or service when executing an order unless that good or service either is directly related to the execution of trades on behalf of its clients/customers or amounts to the provision of substantive research (as defined under UK Law). These requirements may also apply with respect to orders in connection with which the investment adviser receives goods and services under a CCA or other bundled brokerage arrangement. Fund or Trust trades may also implicate UK Law requiring the investment adviser to direct any research portion of a brokerage commission to an account controlled by the investment adviser.

Eaton Vance National Municipal Opportunities Trust 28 SAI dated July 22, 2021

The investment companies sponsored by the investment adviser or certain of its affiliates also may allocate brokerage commissions to acquire information relating to the performance, fees and expenses of such companies and other investment companies, which information is used by the members of the Board of such companies to fulfill their responsibility to oversee the quality of the services provided to various entities, including the investment adviser, to such companies. Such companies may also pay cash for such information.

Municipal obligations considered as investments for a Fund or Trust may also be appropriate for other investment accounts managed by the investment adviser or certain of its affiliates. Whenever decisions are made to buy or sell securities by a Fund or Trust and one or more of such other accounts simultaneously, the investment adviser will allocate the security transactions (including 'new' issues) in a manner which it believes to be equitable under the circumstances. As a result of such allocations, there may be instances where a Fund or Trust will not participate in a transaction that is allocated among other accounts. If an aggregated order cannot be filled completely, allocations will generally be made on a pro rata basis. An order may not be allocated on a pro rata basis where, for example: (i) consideration is given to portfolio managers who have been instrumental in developing or negotiating a particular investment; (ii) consideration is given to an account with specialized investment policies that coincide with the particulars of a specific investment; (iii) pro rata allocation would result in odd-lot or de minimis amounts being allocated to a portfolio or other client; or (iv) where the investment adviser reasonably determines that departure from a pro rata allocation is advisable. While these aggregation and allocation policies could have a detrimental effect on the price or amount of the securities available to a Fund or Trust from time to time, it is the opinion of the members of the Board that the benefits from the investment adviser organization outweigh any disadvantage that may arise from exposure to simultaneous transactions.

The following table shows brokerage commissions paid during the fiscal years ended March 31, 2021, March 31, 2020 and March 31, 2019 as well as the amount of Trust security transactions for the most recent fiscal year (if any) that were directed to firms that provided some Research Services to the investment adviser or its affiliates (see above), and the commissions paid in connection therewith. The Trust did not pay any brokerage commissions to affiliated brokers during the past three fiscal years.

Fiscal Year End Brokerage Commission Paid Amount of Transactions Directed to Firms
Providing Research
Commissions Paid on Transactions
Directed to Firms Providing Research
March 31, 2021 $0 $0 $0
March 31, 2020 $0
March 31, 2019 $0

During the fiscal year ended March 31, 2021, the Trust held no securities of its 'regular brokers or dealers,' as that term is defined in Rule 10b-1 of the 1940 Act.

TAXES

The discussions below and certain disclosure in the Prospectus provide general tax information related to an investment in the shares. Because tax laws are complex and often change, you should consult your tax adviser about the tax consequences of an investment in the Trust. For instance, the Biden administration has proposed a significant number of changes to the U.S. tax laws, including an increase in the maximum tax rate applicable to U.S. corporations and certain individuals, which could potentially have retroactive effect. These changes may significantly alter the after-tax return of the Common Shareholders. Unless otherwise noted, the following tax discussion assumes that you are a U.S. person that is not subject to special rules under the Code, and that you hold the shares as a capital asset within the meaning of Section 1221 of the Code.

A U.S. person means for U.S. federal income tax purposes, a citizen or individual resident of the United States, a corporation (including any entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States or any state thereof or the District of Columbia, an estate the income of which is subject to U.S. federal income taxation regardless of its source, or a trust if (i) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have the authority to control all substantial decisions of the trust or (ii) the trust has a valid election in effect under applicable U.S. Treasury Regulations to be treated as a U.S. person.

Eaton Vance National Municipal Opportunities Trust 29 SAI dated July 22, 2021

The Trust has elected to be treated and intends to qualify each year as a regulated investment company (a 'RIC') under Subchapter M the Code. Accordingly, the Trust intends to satisfy certain requirements relating to sources of its income and diversification of its assets and to distribute substantially all of its investment company taxable income (computed without regard to the dividends-paid deduction), its net tax-exempt income and its net capital gains (after reduction by certain capital loss carryforwards) in accordance with the timing requirements imposed by the Code, so as to maintain its RIC status and generally to avoid paying U.S. federal income or excise tax thereon. If it qualifies for treatment as a RIC and satisfies the above-mentioned distribution requirements, the Trust will not be subject to U.S. federal income tax on income timely paid to its Common Shareholders in the form of dividends.

To qualify as a RIC for U.S. federal income tax purposes, the Trust must derive at least 90% of its annual gross income from dividends, interest, payments with respect to securities loans, gains from the sale or other disposition of stock, securities or foreign currencies, or other income (including, but not limited to, gains from options, futures or forward contracts) derived with respect to its business of investing in stock, securities and currencies, and net income derived from an interest in a 'qualified publicly traded partnership' (as defined in the Code). The Trust must also distribute to its Common Shareholders at least the sum of 90% of its investment company taxable income and 90% of its net tax-exempt interest income for each taxable year.

The Trust must also satisfy certain requirements with respect to the diversification of its assets. The Trust must have, at the close of each quarter of its taxable year, at least 50% of the value of its total assets represented by cash and cash items, U.S. government securities, securities of other RICs, and other securities that, in respect of any one issuer, do not represent more than 5% of the value of the assets of the Trust or more than 10% of the voting securities of that issuer. In addition, at the close of each quarter of its taxable year, not more than 25% of the value of the Trust's assets may be invested, including through corporations in which the Trust owns a 20% or more voting stock interest, in securities (other than U.S. Government securities or the securities of other RICs) of any one issuer, or of two or more issuers that the Trust controls and which are engaged in the same or similar trades or businesses or related trades or businesses, or of one or more qualified publicly traded partnerships.

In order to avoid incurring a nondeductible 4% U.S. federal excise tax obligation, the Code requires that the Trust distribute (or be deemed to have distributed) by December 31 of each calendar year an amount at least equal to the sum of (i) 98% of its ordinary income for such year, (ii) 98.2% of its capital gain net income (which is the excess of its capital gain over its capital loss), generally computed on the basis of the one-year period ending on October 31 of such year (or later if the Trust is permitted and so elects) and (iii) 100% of any ordinary income and capital gain net income from the prior year (as previously computed) that were not paid out during such year and on which the Trust paid no U.S. federal income tax.

If the Trust does not qualify as a RIC for any taxable year, the Trust's taxable income will be subject to corporate income taxes, and all distributions from earnings and profits, including distributions of net capital gain (if any) and net tax-exempt income, will be taxable to the Common Shareholder as ordinary income. Such distributions may be treated as qualified dividend income with respect to Common Shareholders who are individuals and may be eligible for the dividends-received deduction in the case of Common Shareholders taxed as corporations, provided, in each case, certain holding period and other requirements are met. In order to requalify for taxation as a RIC, the Trust may be required to recognize unrealized gains, pay substantial taxes and interest, and make substantial distributions.

The Trust intends to invest a sufficient portion of its assets in tax-exempt municipal obligations so that it will be permitted to pay 'exempt-interest dividends' (as defined under applicable U.S. federal income tax law). Each distribution of exempt-interest dividends, whether paid in cash or reinvested in additional Common Shares, ordinarily will constitute income exempt from regular U.S. federal income tax under current U.S. federal tax law, but it may be subject to state and local taxes. Interest on certain municipal obligations, such as certain private activity bonds, however, is included as an item of tax preference in determining the amount of a taxpayer's alternative minimum taxable income. To the extent that the Trust receives income from such municipal obligations, a portion of the dividends paid by the Trust, although exempt from regular U.S. federal income tax, will be taxable to Common Shareholders to the extent that their tax liability is determined under the AMT. Furthermore, exempt-interest dividends are included in determining what portion, if any, of a person's social security and railroad retirement benefits will be includible in gross income subject to regular U.S. federal income tax.

In addition to exempt-interest dividends, the Trust also may distribute to its shareholders amounts that are treated as long-term capital gain or ordinary income (which may include short-term capital gains). These distributions are generally subject to federal, state and local taxation, depending on a shareholder's situation. Taxable distributions are taxable whether shareholders receive them in cash or in the form of additional shares. A shareholder whose distributions are paid in the form of additional shares under the Dividend Reinvestment Plan generally will be treated as having received a dividend equal to either (i) if the shares are trading below net asset value, the amount of cash allocated to the shareholder for the purchase of shares on its behalf in the open market, or (ii) if shares are trading at or above net asset value, generally the fair market value of the new shares issued to the shareholder.

Eaton Vance National Municipal Opportunities Trust 30 SAI dated July 22, 2021

At least annually, the Trust intends to distribute any net capital gain (which is the excess of net long-term capital gain over net short-term capital loss, in each case determined with reference to certain loss carryforwards), if any, or, alternatively, to retain all or a portion of the year's net capital gain and pay U.S. federal income tax on the retained gain.

Net capital gain distributions designated as capital gains dividends are generally taxable at rates applicable to long-term capital gains regardless of how long a Common Shareholder has held his or her Common Shares. The IRS and the Department of the Treasury have issued regulations that impose special rules in respect of capital gain dividends received through partnership interests constituting 'applicable partnership interests' under Section 1061 of the Code.

If the Trust retains any net capital gain or investment company taxable income, it will be subject to tax at regular corporate rates on the amount retained. If the Trust retains any net capital gain, it may designate the retained amount as undistributed capital gains in a notice to its Common Shareholders who (i) will be required to include in income for U.S. federal income tax purposes, as long-term capital gain, their share of such undistributed amount; (ii) will be entitled to credit their proportionate share of the tax paid by the Trust on such undistributed amount against their U.S. federal income tax liabilities, if any; and (iii) will be entitled to claim refunds to the extent the credit exceeds such liabilities. For U.S. federal income tax purposes, the tax basis of Common Shares owned by a Common Shareholder of the Trust will be increased by an amount equal to the difference between the amount of undistributed capital gains included in the Common Shareholder's gross income under clause (i) and the tax deemed paid by the Common Shareholder under clauses (ii) and (iii) of the preceding sentence. The Trust is not required to, and there can be no assurance the Trust will, make this designation if it retains all or a portion of its net capital gain in a taxable year.

If the Trust makes a distribution to a Common Shareholder in excess of the Trust's current and accumulated earnings and profits in any taxable year, the excess distribution will be treated as a return of capital to the extent of such Common Shareholder's tax basis in its Common Shares, and thereafter as capital gain. A return of capital is not taxable, but it reduces a Common Shareholder's tax basis in its Common Shares, thus reducing any loss or increasing any gain on a subsequent taxable disposition by the Common Shareholder of its Common Shares.

The net investment income of certain U.S. individuals, estates and trusts is subject to a 3.8% Medicare contribution tax. For individuals, the tax is on the lesser of the 'net investment income' and the excess of modified adjusted gross income over $200,000 (or $250,000 if married filing jointly). Net investment income includes, among other things, interest, dividends (other than exempt-interest dividends), and gross income and capital gains derived from passive activities and trading in securities or commodities. Net investment income is reduced by deductions 'properly allocable' to this income.

The Internal Revenue Service ('IRS') currently requires that a RIC that has two or more classes of stock allocate to each such class proportionate amounts of each type of its income (such as exempt-interest, ordinary income and capital gains) based on the percentage of total dividends distributed to each class for the tax year. Accordingly, if the Trust issues preferred shares, it will designate dividends made with respect to Common Shares and preferred shares as consisting of particular types of income (e.g., exempt-interest, net capital gain and ordinary income) in accordance with the proportionate share of each class in the total dividends paid by the Trust during the year.

Dividends and other taxable distributions declared by the Trust in October, November or December to Common Shareholders of record on a specified date in such month and paid during the following January are deemed to have been paid by the Trust on December 31 of the preceding year.

Each Common Shareholder will receive an annual statement summarizing the source and tax status of all distributions (including net capital gains credited to the Common Shareholder but retained by the Trust) after the close of the Trust's taxable year.

The sale or exchange of shares normally will result in capital gain or loss to shareholders. Generally a shareholder's gain or loss will be long-term capital gain or loss if the shares have been held for more than one year, and short-term capital gain or loss if the shares are held for one year or less. Any loss on the sale of shares that have been held for six months or less will be disallowed to the extent of any distribution of exempt-interest dividends received with respect to such shares, unless the shares are of a RIC that declares exempt-interest dividends on a daily basis in an amount equal to at least 90% of its net tax-exempt interest and distributes such dividends on a monthly or more frequent basis. If a shareholder sells or otherwise disposes of shares before holding them for more than six months, any loss on the sale or disposition will be treated as a long-term capital loss to the extent of any capital gain dividends received by the shareholder on such shares. Any loss realized on a sale or exchange of shares of the Trust will be disallowed to the extent those shares of the Trust are replaced by other substantially identical shares of the Trust or other substantially identical stock or securities (including through reinvestment of dividends) within a period of 61 days beginning 30 days before and ending 30 days after the date of disposition of the original shares. In that event, the basis of the replacement shares of the Trust will be adjusted to reflect the disallowed loss.

Eaton Vance National Municipal Opportunities Trust 31 SAI dated July 22, 2021

From time to time, the Trust may make a tender offer for its shares. Shareholders who tender all shares held, or considered to be held, by them will be treated as having sold their shares and generally will realize a capital gain or loss. If a shareholder tenders fewer than all or its shares, such shareholder may be treated as having received a distribution under Section 301 of the Code ('Section 301 distribution') unless the redemption is treated as being either (i) 'substantially disproportionate' with respect to such shareholder or (ii) otherwise 'not essentially equivalent to a dividend' under the relevant rules of the Code. A Section 301 distribution is not treated as a sale or exchange giving rise to a capital gain or loss, but rather is treated as a dividend to the extent supported by the Trust's current and accumulated earnings and profits, with the excess treated as a return of capital reducing the shareholder's tax basis in the Trust shares, and thereafter as capital gain. Where a redeeming shareholder is treated as receiving a dividend, there is a risk that non-tendering shareholders whose interests in the Trust increase as a result of such tender will be treated as having received a taxable distribution from the Trust. The extent of such risk will vary depending upon the particular circumstances of the tender offer, in particular whether such offer is a single and isolated event or is part of a plan for periodically redeeming the shares of the Trust; if isolated, any such risk is likely remote.

Sales charges paid upon a purchase of shares cannot be taken into account for purposes of determining gain or loss on a sale of the Common Shares before the 91st day after their purchase to the extent a sales charge is reduced or eliminated in a subsequent acquisition of Common Shares of the Trust, during the period beginning on the date of such sale and ending on January 31 of the calendar year following the calendar year in which such sale was made, pursuant to a reinvestment or exchange privilege. Any disregarded amounts will result in an adjustment to the Common Shareholder's tax basis in some or all of any other Common Shares acquired.

An investor should be aware that, if Common Shares are purchased shortly before the record date for any taxable distribution (including a capital gain dividend), the purchase price likely will reflect the value of the distribution and the investor then would receive a taxable distribution likely to reduce the trading value of such Common Shares, in effect resulting in a taxable return of some of the purchase price. An investor should also be aware that the benefits of the reduced tax rate applicable to long-term capital gains may be impacted by the application of the AMT to individual Common Shareholders. Further, entities or persons who are 'substantial users' (or persons related to 'substantial users') of facilities financed by industrial development or private activity bonds should consult their tax advisers before purchasing Common Shares of the Trust. 'Substantial user' is defined in applicable Treasury regulations to include a 'non-exempt person' who regularly uses in its trade or business a part of a facility financed from the proceeds of industrial development bonds, and the same definition should apply in the case of private activity bonds.

Any interest on indebtedness incurred or continued to purchase or carry the Trust's Common Shares to which exempt-interest dividends are allocated is not deductible by Common Shareholders in proportion to the percentage that the Trust's distribution of exempt-interest dividends bears to all of the Trust's distributions, excluding capital gain dividends. Under certain applicable rules, the purchase or ownership of Common Shares may be considered to have been made with borrowed funds even though such funds are not directly used for the purchase or ownership of the Common Shares. In addition, if you receive Social Security or certain railroad retirement benefits, you may be subject to U.S. federal income tax on a portion of such benefits as a result of receiving investment income, including exempt-interest dividends and other distributions paid by the Trust.

If the Trust invests in certain pay-in-kind securities, zero coupon securities, deferred interest securities or, in general, any other securities with original issue discount (or with market discount if the Trust elects to include market discount in income currently), the Trust must accrue income on such investments for each taxable year, which generally will be prior to the receipt of the corresponding cash payments. However, the Trust must distribute to Common Shareholders, at least annually, all or substantially all of its investment company taxable income (determined without regard to the deduction for dividends paid) and net tax-exempt income, including such accrued income, to qualify as a RIC and to avoid U.S. federal income and excise taxes. Therefore, the Trust may have to dispose of its portfolio securities under disadvantageous circumstances to generate cash, or may have to leverage itself by borrowing the cash, to satisfy these distribution requirements.

The Trust may hold or acquire municipal obligations that are treated as having 'market discount.' Very generally, market discount is the excess of the stated redemption price of a debt obligation (or in the case of an obligation issued with original issue discount its 'revised issue price') over the purchase price of such obligation. Subject to the discussion below regarding Section 451 of the Code, (i) generally, any gain recognized on the disposition of, and any partial payment of principal on, a debt obligation having market discount is treated as ordinary income to the extent the gain, or principal payment, does not exceed the 'accrued market discount' on such debt obligation, (ii) alternatively, the Trust may elect to accrue market discount currently, in which case the Trust will be required to include the accrued market discount on such debt obligation in the Trust's income (as ordinary income) and thus distribute it over the term of the debt obligation, even though payment of that amount is not received until a later time, upon partial or full repayment or disposition of the debt obligation, and (iii) the rate at which the market discount accrues, and thus is included in the Trust's income, will depend upon which of the permitted accrual methods the Trust elects. The Trust reserves the right to revoke such an election at

Eaton Vance National Municipal Opportunities Trust 32 SAI dated July 22, 2021

any time pursuant to applicable IRS procedures. Notwithstanding the foregoing, effective for taxable years beginning after 2017, Section 451 of the Code generally requires any accrual method taxpayer to take into account items of gross income no later than the time at which such items are taken into account as revenue in the taxpayer's financial statements. However, the Treasury Department has issued final regulations providing that Section 451 does not apply to accrued market discount. If Section 451 were to apply to the accrual of market discount, the Trust would be required to include in income any market discount as it takes the same into account on its financial statements.

The Trust may invest to a significant extent in debt obligations that are in the lowest rating categories or are unrated, including debt obligations of issuers not currently paying interest or who are in default. Investments in debt obligations that are at risk of or in default present special tax issues for the Trust. Tax rules are not entirely clear about issues such as when the Trust may cease to accrue interest, original issue discount or market discount, when and to what extent deductions may be taken for bad debts or worthless securities and how payments received on obligations in default should be allocated between principal and income.

The Trust's investments in options, futures contracts, hedging transactions, forward contracts (to the extent permitted) and certain other transactions will be subject to special tax rules (including mark-to-market, constructive sale, straddle, wash sale, short sale and other rules), the effect of which may be to accelerate income to the Trust, defer Trust losses, cause adjustments in the holding periods of Trust securities, convert capital gain into ordinary income and convert short-term capital losses into long-term capital losses. These rules could therefore affect the amount, timing and character of distributions to investors.

As a result of entering into swap contracts, the Trust may make or receive periodic net payments. The Trust may also make or receive a payment when a swap is terminated prior to maturity through an assignment of the swap or other closing transaction. Periodic net payments will generally constitute ordinary income or deductions, while termination of a swap will generally result in capital gain or loss (which will be a long-term capital gain or loss if the Trust has been a party to a swap for more than one year). With respect to certain types of swaps, the Trust may be required to currently recognize income or loss with respect to future payments on such swaps or may elect under certain circumstances to mark such swaps to market annually for tax purposes as ordinary income or loss. The tax treatment of many types of credit default swaps is uncertain.

The Trust may invest in other securities the U.S. federal income tax treatment of which is uncertain or subject to recharacterization by the IRS. To the extent the tax treatment of such securities or their income differs from the tax treatment expected by the Trust, it could affect the timing or character of income recognized by the Trust, requiring the Trust to purchase or sell securities, or otherwise change its portfolio, in order to comply with the tax rules applicable to RICs under the Code.

The Trust may be required to withhold, for U.S. federal income tax purposes, a certain portion of all taxable distributions payable to Common Shareholders who fail to provide the Trust with their correct taxpayer identification number or make required certifications, or if the Common Shareholders have been notified by the IRS that they are subject to backup withholding. Backup withholding is not an additional tax. Any amounts withheld may be credited against a Common Shareholder's U.S. federal income tax liability.

Under Treasury regulations, if a Common Shareholder realizes a loss on disposition of the Trust's Common Shares of at least $2 million in any single taxable year or $4 million in any combination of taxable years for an individual Common Shareholder or at least $10 million in any single taxable year or $20 million in any combination of taxable years for a corporate shareholder, the shareholder must file with the IRS a disclosure statement on Form 8886. Direct Common Shareholders of portfolio securities are in many cases excepted from this reporting requirement, but under current guidance, Common Shareholders of a RIC are not excepted. The fact that a loss is reportable under these regulations does not affect the legal determination of whether the taxpayer's treatment of the loss is proper. Shareholders should consult their tax advisers to determine the applicability of these regulations in light of their individual circumstances. Under certain circumstances, certain tax-exempt entities and their managers may be subject to excise tax if they are parties to certain reportable transactions.

Distributions by the Trust to Common Shareholders that are not 'U.S. persons' within the meaning of the Code ('foreign shareholders') properly reported by the Trust as (1) capital gain dividends, (2) short-term capital gain dividends, (3) interest-related dividends, as defined and subject to certain conditions described below, and (4) exempt-interest dividends generally are not subject to withholding of U.S. federal income tax.

In general, the Code defines (1) 'short-term capital gain dividends' as distributions of net short-term capital gains in excess of net long-term capital losses and (2) 'interest-related dividends' as distributions from U.S. source interest income of types similar to those not subject to U.S. federal income tax if earned directly by an individual foreign shareholder, in each case to the extent such distributions are properly reported as such by the Trust in a written notice to Common Shareholders. The exceptions to withholding for capital gain dividends and short-term capital gain dividends do

Eaton Vance National Municipal Opportunities Trust 33 SAI dated July 22, 2021

not apply to (A) distributions to an individual foreign shareholder who is present in the United States for a period or periods aggregating 183 days or more during the year of the distribution and (B) distributions attributable to gain that is treated as effectively connected with the conduct by the foreign shareholder of a trade or business within the United States under special rules regarding the disposition of U.S. real property interests. The exception to withholding for interest-related dividends does not apply to distributions to a foreign shareholder (A) that has not provided a satisfactory statement that the beneficial owner is not a U.S. person, (B) to the extent that the dividend is attributable to certain interest on an obligation if the foreign shareholder is the issuer or is a 10% shareholder of the issuer, (C) that is within certain foreign countries that have inadequate information exchange with the United States, or (D) to the extent the dividend is attributable to interest paid by a person that is a related person of the foreign shareholder and the foreign shareholder is a controlled foreign corporation. The Trust is permitted to report such part of its dividends as interest-related and/or short-term capital gain dividends as are eligible, but is not required to do so. In the case of shares held through an intermediary, the intermediary may withhold even if the Trust reports all or a portion of a payment as an interest-related or short-term capital gain dividend to shareholders. Foreign shareholders should contact their intermediaries regarding the application of these rules to their accounts.

Foreign shareholders with respect to whom income from the Trust is effectively connected with a trade or business conducted by the foreign shareholder within the United States will in general be subject to U.S. federal income tax on the income derived from the Trust at the graduated rates applicable to U.S. citizens, residents or domestic corporations, whether such income is received in cash or reinvested in shares of the Trust and, in the case of a foreign corporation, may also be subject to a branch profits tax. If a foreign shareholder is eligible for the benefits of a tax treaty, any effectively connected income or gain will generally be subject to U.S. federal income tax on a net basis only if it is also attributable to a permanent establishment maintained by the shareholder in the United States. More generally, foreign shareholders who are residents in a country with an income tax treaty with the United States may obtain different tax results than those described herein, and are urged to consult their tax advisers. Distributions by the Trust to foreign shareholders other than capital gain dividends, short-term capital gain dividends, interest-related dividends, and exempt-interest dividends (e.g., dividends attributable to dividend and foreign-source interest income or to short-term capital gains or U.S. source interest income to which the exception from withholding described above does not apply) are generally subject to withholding of U.S. federal income tax at a rate of 30% (or lower applicable treaty rate).

A foreign shareholder is not, in general, subject to U.S. federal income tax on gains (and is not allowed a deduction for losses) realized on the sale of Common Shares of the Trust unless (i) such gain is effectively connected with the conduct by the foreign shareholder of a trade or business within the United States, (ii) in the case of a foreign shareholder that is an individual, the shareholder is present in the United States for a period or periods aggregating 183 days or more during the year of the sale and certain other conditions are met, or (iii) the special rules relating to gain attributable to the sale or exchange of 'U.S. real property interests' apply to the foreign shareholder's sale of Common Shares of the Trust.

In order to qualify for any exemptions from withholding described above or for lower withholding tax rates under income tax treaties, or to establish an exemption from backup withholding, a foreign shareholder must comply with special certification and filing requirements relating to its non-U.S. status (including, in general, furnishing an IRS Form W-8BEN, W-8BEN-E or substitute form). Foreign shareholders should consult their tax advisers in this regard.

Special rules (including withholding and reporting requirements) apply to foreign partnerships and those holding Trust shares through foreign partnerships. Additional considerations may apply to foreign trusts and estates. Investors holding Trust shares through foreign entities should consult their tax advisers about their particular situation.

Sections 1471-1474 of the Code and the U.S. Treasury and IRS guidance issued thereunder (collectively, 'FATCA') generally require the Trust to obtain information sufficient to identify the status of each of its Common Shareholders under FATCA or under an applicable intergovernmental agreement (an 'IGA') between the United States and a foreign government. If a Common Shareholder fails to provide the requested information or otherwise fails to comply with FATCA or an IGA, the Trust may be required to withhold under FATCA at a rate of 30% with respect to that Common Shareholder on ordinary dividends it pays. The IRS and Department of Treasury have issued proposed regulations providing that these withholding rules will not be applicable to the gross proceeds of share redemptions or capital gain dividends the Trust pays. If a payment by the Trust is subject to FATCA withholding, the Trust is required to withhold even if such payment would otherwise be exempt from withholding under the rules applicable to foreign Common Shareholders described above (e.g., interest-related dividends).

Each prospective investor is urged to consult its tax adviser regarding the applicability of FATCA and any other reporting requirements with respect to the prospective investor's own situation, including investments through an intermediary.

The Code, with respect to all of the foregoing matters and other matters that may affect the Trust or the Common Shareholders, is constantly subject to change by Congress. In recent years there have been significant changes in the Code, and Congress is currently considering further significant changes to U.S. federal tax law. For instance, the Biden administration has proposed a significant number of changes to the U.S. tax laws, including an increase in the maximum

Eaton Vance National Municipal Opportunities Trust 34 SAI dated July 22, 2021

tax rate applicable to U.S. corporations and certain individuals, which could potentially have retroactive effect. These changes may significantly alter the after-tax return of the Common Shareholders. It is not possible at this time to predict whether or to what extent any changes will be made to the Code. Prospective investors should note that the Trust will not undertake to advise investors of any legislative or other developments. Such investors should consult their own tax advisers regarding pending and proposed legislation or other changes.

The foregoing briefly summarizes some of the important U.S. federal income tax consequences to Common Shareholders of investing in Common Shares, reflects the U.S. federal tax law as of the date of this SAI, and does not address special tax rules applicable to certain types of investors, such as corporate investors. This discussion is based upon current provisions of the Code, the regulations promulgated thereunder, and judicial and administrative ruling authorities, all of which are subject to change or differing interpretations by the courts or the IRS retroactively or prospectively. No attempt has been made to present a complete explanation of the U.S. federal tax treatment of the Trust or the implications to Common Shareholders, and the discussions here and in the prospectus are not intended as a substitute for careful tax planning.

Investors should consult their own tax advisers regarding other U.S. federal, as well as state or local, tax consequences of investing in the Trust that may be applicable in their particular circumstances, as well as any proposed tax law changes.

OTHER INFORMATION

The Trust is an organization of the type commonly known as a 'Massachusetts business trust.' Under Massachusetts law, shareholders of such a trust may, in certain circumstances, be held personally liable as partners for the obligations of the trust. The Declaration of Trust contains an express disclaimer of shareholder liability in connection with the Trust property or the acts, obligations or affairs of the Trust. The Declaration of Trust, in coordination with the Trust's Amended and Restated By-laws, also provides for indemnification out of the Trust property of any shareholder held personally liable for the claims and liabilities to which a shareholder may become subject by reason of being or having been a shareholder. Thus, the risk of a shareholder incurring financial loss on account of shareholder liability is limited to circumstances in which the Trust itself is unable to meet its obligations. The Trust has been advised by its counsel that the risk of any shareholder incurring any liability for the obligations of the Trust is remote.

The Declaration of Trust provides that the Trustees will not be liable for errors of judgment or mistakes of fact or law; but nothing in the Declaration of Trust protects a Trustee against any liability to the Trust or its shareholders to which he or she would otherwise be subject by reason of willful misfeasance, bad faith, gross negligence, or reckless disregard of the duties involved in the conduct of his or her office. Voting rights are not cumulative, which means that the holders of more than 50% of the shares voting for the election of Trustees can elect 100% of the Trustees and, in such event, the holders of the remaining less than 50% of the shares voting on the matter will not be able to elect any Trustees.

The Declaration of Trust provides that no person shall serve as a Trustee if shareholders holding two-thirds of the outstanding shares have removed him from that office either by a written declaration filed with the Trust's custodian or by votes cast at a meeting called for that purpose. The Declaration of Trust further provides that the Trustees of the Trust shall promptly call a meeting of the shareholders for the purpose of voting upon a question of removal of any such Trustee or Trustees when requested in writing so to do by the record holders of not less than 10 per centum of the outstanding shares.

The Trust's Prospectus, any related Prospectus Supplement, and this SAI do not contain all of the information set forth in the Registration Statement that the Trust has filed with the SEC. The complete Registration Statement may be obtained from the SEC through the website www.sec.gov, or upon payment of the fee prescribed by its Rules and Regulations.

CUSTODIAN

State Street Bank and Trust Company ('State Street'), State Street Financial Center, One Lincoln Street, Boston, MA 02111, is the custodian of the Trust and will maintain custody of the securities and cash of the Trust. State Street maintains the Trust's general ledger and computes net asset value per share at least weekly. State Street also attends to details in connection with the sale, exchange, substitution, transfer and other dealings with the Trust's investments, and receives and disburses all funds. State Street also assists in preparation of shareholder reports and the electronic filing of such reports with the SEC.

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Deloitte & Touche LLP ('Deloitte'), 200 Berkeley Street, Boston, MA 02116, independent registered public accounting firm, audits the Trust's financial statements. Deloitte and/or its affiliates provide other audit, tax and related services to the Trust.

Eaton Vance National Municipal Opportunities Trust 35 SAI dated July 22, 2021

POTENTIAL CONFLICTS OF INTEREST

As a diversified global financial services firm, Morgan Stanley engages in a broad spectrum of activities, including financial advisory services, investment management activities, lending, commercial banking, sponsoring and managing private investment funds, engaging in broker-dealer transactions and principal securities, commodities and foreign exchange transactions, research publication and other activities. In the ordinary course of its business, Morgan Stanley is a full-service investment banking and financial services firm and therefore engages in activities where Morgan Stanley's interests or the interests of its clients may conflict with the interests of a Trust, Fund or Portfolio, if applicable, (collectively for the purposes of this section, 'Fund' or 'Funds'). Morgan Stanley advises clients and sponsors, manages or advises other investment funds and investment programs, accounts and businesses (collectively, together with the Funds, any new or successor funds, programs, accounts or businesses, the ''Affiliated Investment Accounts'') with a wide variety of investment objectives that in some instances may overlap or conflict with a Fund's investment objectives and present conflicts of interest. In addition, Morgan Stanley may also from time to time create new or successor Affiliated Investment Accounts that may compete with a Fund and present similar conflicts of interest. The discussion below enumerates certain actual, apparent and potential conflicts of interest. There is no assurance that conflicts of interest will be resolved in favor of Fund shareholders and, in fact, they may not be. Conflicts of interest not described below may also exist.

Material Non-public and Other Information. It is expected that confidential or material non-public information regarding an investment or potential investment opportunity may become available to the investment adviser. If such information becomes available, the investment adviser may be precluded (including by applicable law or internal policies or procedures) from pursuing an investment or disposition opportunity with respect to such investment or investment opportunity.

The investment adviser may also from time to time be subject to contractual ''stand-still'' obligations and/or confidentiality obligations that may restrict its ability to trade in certain investments on a Fund's behalf. In addition, the investment adviser may be precluded from disclosing such information to an investment team, even in circumstances in which the information would be beneficial if disclosed. Therefore, the investment team may not be provided access to material non-public information in the possession of Morgan Stanley that might be relevant to an investment decision to be made on behalf of a Fund, and the investment team may initiate a transaction or sell an investment that, if such information had been known to it, may not have been undertaken. In addition, certain members of the investment team may be recused from certain investment-related discussions so that such members do not receive information that would limit their ability to perform functions of their employment with the investment adviser or its affiliates unrelated to that of a Fund. Furthermore, access to certain parts of Morgan Stanley may be subject to third party confidentiality obligations and to information barriers established by Morgan Stanley in order to manage potential conflicts of interest and regulatory restrictions, including without limitation joint transaction restrictions pursuant to the 1940 Act. Accordingly, the investment adviser's ability to source investments from other business units within Morgan Stanley may be limited and there can be no assurance that the investment adviser will be able to source any investments from any one or more parts of the Morgan Stanley network.

The investment adviser may restrict its investment decisions and activities on behalf of the Funds in various circumstances, including because of applicable regulatory requirements or information held by the investment adviser or Morgan Stanley. The investment adviser might not engage in transactions or other activities for, or enforce certain rights in favor of, a Fund due to Morgan Stanley's activities outside the Funds. In instances where trading of an investment is restricted, the investment adviser may not be able to purchase or sell such investment on behalf of a Fund, resulting in the Fund's inability to participate in certain desirable transactions. This inability to buy or sell an investment could have an adverse effect on a Fund's portfolio due to, among other things, changes in an investment's value during the period its trading is restricted. Also, in situations where the investment adviser is required to aggregate its positions with those of other Morgan Stanley business units for position limit calculations, the investment adviser may have to refrain from making investments due to the positions held by other Morgan Stanley business units or their clients. There may be other situations where the investment adviser refrains from making an investment due to additional disclosure obligations, regulatory requirements, policies, and reputational risk, or the investment adviser may limit purchases or sales of securities in respect of which Morgan Stanley is engaged in an underwriting or other distribution capacity.

Morgan Stanley has established certain information barriers and other policies to address the sharing of information between different businesses within Morgan Stanley. As a result of information barriers, the investment adviser generally will not have access, or will have limited access, to certain information and personnel in other areas of Morgan Stanley relating to business transactions for clients (including transactions in investing, banking, prime brokerage and certain other areas), and generally will not manage the Funds with the benefit of the information held by such other areas. Morgan Stanley, due to its access to and knowledge of funds, markets and securities based on its prime brokerage and other businesses, may make decisions based on information or take (or refrain from taking) actions with respect to interests in investments of the kind held (directly or indirectly) by the Funds in a manner that may be adverse to the Funds, and will not have any obligation or other duty to share information with the investment adviser.

Eaton Vance National Municipal Opportunities Trust 36 SAI dated July 22, 2021

In limited circumstances, however, including for purposes of managing business and reputational risk, and subject to policies and procedures, Morgan Stanley personnel, including personnel of the investment adviser, on one side of an information barrier may have access to information and personnel on the other side of the information barrier through 'wall crossings.' The investment adviser faces conflicts of interest in determining whether to engage in such wall crossings. Information obtained in connection with such wall crossings may limit or restrict the ability of the investment adviser to engage in or otherwise effect transactions on behalf of the Funds (including purchasing or selling securities that the investment adviser may otherwise have purchased or sold for a Fund in the absence of a wall crossing). In managing conflicts of interest that arise because of the foregoing, the investment adviser generally will be subject to fiduciary requirements. The investment adviser may also implement internal information barriers or ethical walls, and the conflicts described herein with respect to information barriers and otherwise with respect to Morgan Stanley and the investment adviser will also apply internally within the investment adviser. As a result, a Fund may not be permitted to transact in (e.g., dispose of a security in whole or in part) during periods when it otherwise would have been able to do so, which could adversely affect a Fund. Other investors in the security that are not subject to such restrictions may be able to transact in the security during such periods. There may also be circumstances in which, as a result of information held by certain portfolio management teams in the investment adviser, the investment adviser limits an activity or transaction for a Fund, including if the Fund is managed by a portfolio management team other than the team holding such information.

Investments by Morgan Stanley and its Affiliated Investment Accounts. In serving in multiple capacities to Affiliated Investment Accounts, Morgan Stanley, including the investment adviser and its investment teams, may have obligations to other clients or investors in Affiliated Investment Accounts, the fulfillment of which may not be in the best interests of a Fund or its shareholders. A Fund's investment objectives may overlap with the investment objectives of certain Affiliated Investment Accounts. As a result, the members of an investment team may face conflicts in the allocation of suitable investment opportunities among a Fund and other investment funds, programs, accounts and businesses advised by or affiliated with the investment adviser. Certain Affiliated Investment Accounts may provide for higher management or incentive fees or greater expense reimbursements or overhead allocations, all of which may contribute to this conflict of interest and create an incentive for the investment adviser to favor such other accounts.

Morgan Stanley currently invests and plans to continue to invest on its own behalf and on behalf of its Affiliated Investment Accounts in a wide variety of investment opportunities globally. Morgan Stanley and its Affiliated Investment Accounts, to the extent consistent with applicable law and policies and procedures, will be permitted to invest in investment opportunities without making such opportunities available to a Fund beforehand. Subject to the foregoing, Morgan Stanley may offer investments that fall into the investment objectives of an Affiliated Investment Account to such account or make such investment on its own behalf, even though such investment also falls within a Fund's investment objectives. A Fund may invest in opportunities that Morgan Stanley and/or one or more Affiliated Investment Accounts has declined, and vice versa. All of the foregoing may reduce the number of investment opportunities available to a Fund and may create conflicts of interest in allocating investment opportunities. Investors should note that the conflicts inherent in making such allocation decisions may not always be resolved to a Fund's advantage. There can be no assurance that a Fund will have an opportunity to participate in certain opportunities that fall within their investment objectives.

To seek to reduce potential conflicts of interest and to attempt to allocate such investment opportunities in a fair and equitable manner, the investment adviser has implemented allocation policies and procedures. These policies and procedures are intended to give all clients of the investment adviser, including the Funds, fair access to investment opportunities consistent with the requirements of organizational documents, investment strategies, applicable laws and regulations, and the fiduciary duties of the investment adviser. Each client of the investment adviser that is subject to the allocation policies and procedures, including each Fund, is assigned an investment team and portfolio manager(s) by the investment adviser. The investment team and portfolio managers review investment opportunities and will decide with respect to the allocation of each opportunity considering various factors and in accordance with the allocation policies and procedures. The allocation policies and procedures are subject to change. Investors should note that the conflicts inherent in making such allocation decisions may not always be resolved to the advantage of a Fund.

It is possible that Morgan Stanley or an Affiliated Investment Account, including another Eaton Vance fund, will invest in or advise a company that is or becomes a competitor of a company of which a Fund holds an investment. Such investment could create a conflict between the Fund, on the one hand, and Morgan Stanley or the Affiliated Investment Account, on the other hand. In such a situation, Morgan Stanley may also have a conflict in the allocation of its own resources to the portfolio investment. Furthermore, certain Affiliated Investment Accounts will be focused primarily on investing in other funds which may have strategies that overlap and/or directly conflict and compete with a Fund.

Eaton Vance National Municipal Opportunities Trust 37 SAI dated July 22, 2021

In addition, certain investment professionals who are involved in a Fund's activities remain responsible for the investment activities of other Affiliated Investment Accounts managed by the investment adviser and its affiliates, and they will devote time to the management of such investments and other newly created Affiliated Investment Accounts (whether in the form of funds, separate accounts or other vehicles), as well as their own investments. In addition, in connection with the management of investments for other Affiliated Investment Accounts, members of Morgan Stanley and its affiliates may serve on the boards of directors of or advise companies which may compete with a Fund's portfolio investments. Moreover, these Affiliated Investment Accounts managed by Morgan Stanley and its affiliates may pursue investment opportunities that may also be suitable for a Fund.

It should be noted that Morgan Stanley may, directly or indirectly, make large investments in certain of its Affiliated Investment Accounts, and accordingly Morgan Stanley's investment in a Fund may not be a determining factor in the outcome of any of the foregoing conflicts. Nothing herein restricts or in any way limits the activities of Morgan Stanley, including its ability to buy or sell interests in, or provide financing to, equity and/or debt instruments, funds or portfolio companies, for its own accounts or for the accounts of Affiliated Investment Accounts or other investment funds or clients in accordance with applicable law.

Different clients of the investment adviser, including a Fund, may invest in different classes of securities of the same issuer, depending on the respective clients' investment objectives and policies. As a result, the investment adviser and its affiliates, at times, will seek to satisfy fiduciary obligations to certain clients owning one class of securities of a particular issuer by pursuing or enforcing rights on behalf of those clients with respect to such class of securities, and those activities may have an adverse effect on another client which owns a different class of securities of such issuer. For example, if one client holds debt securities of an issuer and another client holds equity securities of the same issuer, if the issuer experiences financial or operational challenges, the investment adviser and its affiliates may seek a liquidation of the issuer on behalf of the client that holds the debt securities, whereas the client holding the equity securities may benefit from a reorganization of the issuer. Thus, in such situations, the actions taken by the investment adviser or its affiliates on behalf of one client can negatively impact securities held by another client. These conflicts also exist as between the investment adviser's clients, including the Funds, and the Affiliated Investment Accounts managed by Morgan Stanley.

The investment adviser and its affiliates may give advice and recommend securities to other clients which may differ from advice given to, or securities recommended or bought for, a Fund even though such other clients' investment objectives may be similar to those of the Fund.

The investment adviser and its affiliates manage long and short portfolios. The simultaneous management of long and short portfolios creates conflicts of interest in portfolio management and trading in that opposite directional positions may be taken in client accounts managed by the same investment team, and creates risks such as: (i) the risk that short sale activity could adversely affect the market value of long positions in one or more portfolios (and vice versa) and (ii) the risks associated with the trading desk receiving opposing orders in the same security simultaneously. The investment adviser and its affiliates have adopted policies and procedures that are reasonably designed to mitigate these conflicts. In certain circumstances, the investment adviser invest on behalf of itself in securities and other instruments that would be appropriate for, held by, or may fall within the investment guidelines of its clients, including a Fund. At times, the investment adviser will give advice or take action for its own accounts that differs from, conflicts with, or is adverse to advice given or action taken for any client.

From time to time, conflicts also arise due to the fact that certain securities or instruments maybe held in some client accounts, including a Fund, but not in others, or the client accounts may have different levels of holdings in certain securities or instruments, and because the accounts pay different levels of fees to the investment adviser. In addition, at times an investment adviser's investment team will give advice or take action with respect to the investments of one or more clients that is not given or taken with respect to other clients with similar investment programs, objectives, and strategies. Accordingly, clients with similar strategies will not always hold the same securities or instruments or achieve the same performance. The investment adviser's investment teams also advise clients with conflicting programs, objectives or strategies. These conflicts also exist as between the investment adviser's clients, including the Funds, and the Affiliated Investment Accounts managed by Morgan Stanley.

The investment adviser maintains separate trading desks by investment team and generally based on asset class, including two trading desks trading equity securities. These trading desks operate independently of one another. The two equity trading desks do not share information. The separate equity trading desks may result in one desk competing against the other desk when implementing buy and sell transactions, possibly causing certain accounts to pay more or receive less for a security than other accounts. In addition, Morgan Stanley and its affiliates maintain separate trading desks that operate independently of each other and do not share information with the investment adviser. The Morgan Stanley and affiliate trading desks may compete against the investment adviser trading desks when implementing buy and sell transactions, possibly causing certain Affiliated Investment Accounts to pay more or receive less for a security than other Affiliated Investment Accounts.

Eaton Vance National Municipal Opportunities Trust 38 SAI dated July 22, 2021

Payments to Broker-Dealers and Other Financial Intermediaries. The investment adviser and/or EVD may pay compensation, out of their own funds and not as an expense of the Funds, to certain financial intermediaries (which may include affiliates of the investment adviser and EVD), including recordkeepers and administrators of various deferred compensation plans, in connection with the sale, distribution, marketing and retention of shares of the Funds and/or shareholder servicing. For example, the investment adviser or EVD may pay additional compensation to a financial intermediary for, among other things, promoting the sale and distribution of Fund shares, providing access to various programs, mutual fund platforms or preferred or recommended mutual fund lists that may be offered by a financial intermediary, granting EVD access to a financial intermediary's financial advisors and consultants, providing assistance in the ongoing education and training of a financial intermediary's financial personnel, furnishing marketing support, maintaining share balances and/or for sub-accounting, recordkeeping, administrative, shareholder or transaction processing services. Such payments are in addition to any distribution fees, shareholder servicing fees and/or transfer agency fees that may be payable by the Funds. The additional payments may be based on various factors, including level of sales (based on gross or net sales or some specified minimum sales or some other similar criteria related to sales of the Funds and/or some or all other Eaton Vance funds), amount of assets invested by the financial intermediary's customers (which could include current or aged assets of the Funds and/or some or all other Eaton Vance funds), a Fund's advisory fee, some other agreed upon amount or other measures as determined from time to time by the investment adviser and/or EVD. The amount of these payments may be different for different financial intermediaries.

The prospect of receiving, or the receipt of, additional compensation, as described above, by financial intermediaries may provide such financial intermediaries and their financial advisors and other salespersons with an incentive to favor sales of shares of the Funds over other investment options with respect to which these financial intermediaries do not receive additional compensation (or receives lower levels of additional compensation). These payment arrangements, however, will not change the price that an investor pays for shares of the Funds or the amount that the Funds receive to invest on behalf of an investor. Investors may wish to take such payment arrangements into account when considering and evaluating any recommendations relating to Fund shares and should review carefully any disclosures provided by financial intermediaries as to their compensation.

Morgan Stanley Trading and Principal Investing Activities. Notwithstanding anything to the contrary herein, Morgan Stanley will generally conduct its sales and trading businesses, publish research and analysis, and render investment advice without regard for a Fund's holdings, although these activities could have an adverse impact on the value of one or more of the Fund's investments, or could cause Morgan Stanley to have an interest in one or more portfolio investments that is different from, and potentially adverse to that of a Fund. Furthermore, from time to time, the investment adviser or its affiliates may invest 'seed' capital in a Fund, typically to enable the Fund to commence investment operations and/or achieve sufficient scale. The investment adviser and its affiliates may hedge such seed capital exposure by investing in derivatives or other instruments expected to produce offsetting exposure. Such hedging transactions, if any, would occur outside of a Fund.

Morgan Stanley's sales and trading, financing and principal investing businesses (whether or not specifically identified as such, and including Morgan Stanley's trading and principal investing businesses) will not be required to offer any investment opportunities to a Fund. These businesses may encompass, among other things, principal trading activities as well as principal investing.

Morgan Stanley's sales and trading, financing and principal investing businesses have acquired or invested in, and in the future may acquire or invest in, minority and/or majority control positions in equity or debt instruments of diverse public and/or private companies. Such activities may put Morgan Stanley in a position to exercise contractual, voting or creditor rights, or management or other control with respect to securities or loans of portfolio investments or other issuers, and in these instances Morgan Stanley may, in its discretion and subject to applicable law, act to protect its own interests or interests of clients, and not a Fund's interests.

Subject to the limitations of applicable law, a Fund may purchase from or sell assets to, or make investments in, companies in which Morgan Stanley has or may acquire an interest, including as an owner, creditor or counterparty.

Morgan Stanley's Investment Banking Activities. Morgan Stanley advises clients on a variety of mergers, acquisitions, restructuring, bankruptcy and financing transactions. Morgan Stanley may act as an advisor to clients, including other investment funds that may compete with a Fund and with respect to investments that a Fund may hold. Morgan Stanley may give advice and take action with respect to any of its clients or proprietary accounts that may differ from the advice given, or may involve an action of a different timing or nature than the action taken, by a Fund. Morgan Stanley may give advice and provide recommendations to persons competing with a Fund and/or any of a Fund's investments that are contrary to the Fund's best interests and/or the best interests of any of its investments.

Eaton Vance National Municipal Opportunities Trust 39 SAI dated July 22, 2021

Morgan Stanley could be engaged in financial advising, whether on the buy-side or sell-side, or in financing or lending assignments that could result in Morgan Stanley's determining in its discretion or being required to act exclusively on behalf of one or more third parties, which could limit a Fund's ability to transact with respect to one or more existing or potential investments. Morgan Stanley may have relationships with third-party funds, companies or investors who may have invested in or may look to invest in portfolio companies, and there could be conflicts between a Fund's best interests, on the one hand, and the interests of a Morgan Stanley client or counterparty, on the other hand.

To the extent that Morgan Stanley advises creditor or debtor companies in the financial restructuring of companies either prior to or after filing for protection under Chapter 11 of the U.S. Bankruptcy Code or similar laws in other jurisdictions, the investment adviser's flexibility in making investments in such restructurings on a Fund's behalf may be limited. Morgan Stanley could provide investment banking services to competitors of portfolio companies, as well as to private equity and/or private credit funds; such activities may present Morgan Stanley with a conflict of interest vis-a-vis a Fund's investment and may also result in a conflict in respect of the allocation of investment banking resources to portfolio companies.

To the extent permitted by applicable law, Morgan Stanley may provide a broad range of financial services to companies in which a Fund invests, including strategic and financial advisory services, interim acquisition financing and other lending and underwriting or placement of securities, and Morgan Stanley generally will be paid fees (that may include warrants or other securities) for such services. Morgan Stanley will not share any of the foregoing interest, fees and other compensation received by it (including, for the avoidance of doubt, amounts received by the investment adviser) with a Fund, and any advisory fees payable will not be reduced thereby.

Morgan Stanley may be engaged to act as a financial advisor to a company in connection with the sale of such company, or subsidiaries or divisions thereof, may represent potential buyers of businesses through its mergers and acquisition activities and may provide lending and other related financing services in connection with such transactions. Morgan Stanley's compensation for such activities is usually based upon realized consideration and is usually contingent, in substantial part, upon the closing of the transaction. Under these circumstances, a Fund may be precluded from participating in a transaction with or relating to the company being sold or participating in any financing activity related to merger or acquisition.

To meet applicable regulatory requirements, there are periods when the investment adviser will not engage in certain types of transactions in the securities of companies for which a broker-dealer affiliated with Morgan Stanley is performing investment banking services. Fund shareholders will not receive notice of such instances. In particular, when a broker-dealer affiliated with Morgan Stanley is engaged in an underwriting or other distribution of securities of a company, the investment adviser may be prohibited from purchasing such securities on behalf of a Fund. In addition, under certain circumstances, the investment adviser generally will not initiate transactions in the securities of companies with respect to which affiliates of the investment adviser may have controlling interests or are affiliated.

The investment adviser believes that the nature and range of clients to whom Morgan Stanley and its subsidiaries render investment banking and other services is such that it would be inadvisable to exclude these companies from the Fund's portfolio.

Morgan Stanley's Marketing Activities. Morgan Stanley is engaged in the business of underwriting, syndicating, brokering, administering, servicing, arranging and advising on the distribution of a wide variety of securities and other investments in which a Fund may invest. Subject to the restrictions of the 1940 Act, including Sections 10(f) and 17(e) thereof, a Fund may invest in transactions in which Morgan Stanley acts as underwriter, placement agent, syndicator, broker, administrative agent, servicer, advisor, arranger or structuring agent and receives fees or other compensation from the sponsors of such products or securities. Any fees earned by Morgan Stanley in such capacity will not be shared with the investment adviser or the Funds. Certain conflicts of interest, in addition to the receipt of fees or other compensation, would be inherent in these transactions. Moreover, the interests of one of Morgan Stanley's clients with respect to an issuer of securities in which a Fund has an investment may be adverse to the investment adviser's or a Fund's best interests. In conducting the foregoing activities, Morgan Stanley will be acting for its other clients and will have no obligation to act in the investment adviser's or a Fund's best interests.

Client Relationships. Morgan Stanley has existing and potential relationships with a significant number of corporations, institutions and individuals. In providing services to its clients, Morgan Stanley may face conflicts of interest with respect to activities recommended to or performed for such clients, on the one hand, and a Fund, its shareholders or the entities in which the Fund invests, on the other hand. In addition, these client relationships may present conflicts of interest in determining whether to offer certain investment opportunities to a Fund.

In acting as principal or in providing advisory and other services to its other clients, Morgan Stanley may engage in or recommend activities with respect to a particular matter that conflict with or are different from activities engaged in or recommended by the investment adviser on a Fund's behalf.

Eaton Vance National Municipal Opportunities Trust 40 SAI dated July 22, 2021

Principal Investments. To the extent permitted by applicable law, there may be situations in which a Fund's interests may conflict with the interests of one or more general accounts of Morgan Stanley and its affiliates or accounts managed by Morgan Stanley or its affiliates. This may occur because these accounts hold public and private debt and equity securities of many issuers which may be or become portfolio companies, or from whom portfolio companies may be acquired.

Transactions with Portfolio Companies of Affiliated Investment Accounts. The companies in which a Fund may invest may be counterparties to or participants in agreements, transactions or other arrangements with portfolio companies or other entities of portfolio investments of Affiliated Investment Accounts (for example, a company in which a Fund invests may retain a company in which an Affiliated Investment Account invests to provide services or may acquire an asset from such company or vice versa). Certain of these agreements, transactions and arrangements involve fees, servicing payments, rebates and/or other benefits to Morgan Stanley or its affiliates. For example, portfolio entities may, including at the encouragement of Morgan Stanley, enter into agreements regarding group procurement and/or vendor discounts. Morgan Stanley and its affiliates may also participate in these agreements and may realize better pricing or discounts as a result of the participation of portfolio entities. To the extent permitted by applicable law, certain of these agreements may provide for commissions or similar payments and/or discounts or rebates to be paid to a portfolio entity of an Affiliated Investment Account, and such payments or discounts or rebates may also be made directly to Morgan Stanley or its affiliates. Under these arrangements, a particular portfolio company or other entity may benefit to a greater degree than the other participants, and the funds, investment vehicles and accounts (which may or may not include a Fund) that own an interest in such entity will receive a greater relative benefit from the arrangements than the Eaton Vance funds, investment vehicles or accounts that do not own an interest therein. Fees and compensation received by portfolio companies of Affiliated Investment Accounts in relation to the foregoing will not be shared with a Fund or offset advisory fees payable.

Investments in Portfolio Investments of Other Funds. To the extent permitted by applicable law, when a Fund invests in certain companies or other entities, other funds affiliated with the investment adviser may have made or may be making an investment in such companies or other entities. Other funds that have been or may be managed by the investment adviser may invest in the companies or other entities in which a Fund has made an investment. Under such circumstances, a Fund and such other funds may have conflicts of interest (e.g., over the terms, exit strategies and related matters, including the exercise of remedies of their respective investments). If the interests held by a Fund are different from (or take priority over) those held by such other funds, the investment adviser may be required to make a selection at the time of conflicts between the interests held by such other funds and the interests held by a Fund.

Allocation of Expenses. Expenses may be incurred that are attributable to a Fund and one or more other Affiliated Investment Accounts (including in connection with issuers in which a Fund and such other Affiliated Investment Accounts have overlapping investments). The allocation of such expenses among such entities raises potential conflicts of interest. The investment adviser and its affiliates intend to allocate such common expenses among a Fund and any such other Affiliated Investment Accounts on a pro rata basis or in such other manner as the investment adviser deems to be fair and equitable or in such other manner as may be required by applicable law.

Temporary Investments. To more efficiently invest short-term cash balances held by a Fund, the investment adviser may invest such balances on an overnight 'sweep' basis in shares of one or more money market funds or other short-term vehicles. It is anticipated that the investment adviser to these money market funds or other short-term vehicles may be the investment adviser (or an affiliate) to the extent permitted by applicable law, including Rule 12d1-1 under the 1940 Act. The Fund may invest in Eaton Vance Cash Reserves Fund, LLC (Cash Reserves Fund), an affiliated investment company managed by Eaton Vance, for this purpose. Eaton Vance does not currently receive a fee for advisory services provided to Cash Reserves Fund.

Transactions with Affiliates. The investment adviser and any investment sub-adviser might purchase securities from underwriters or placement agents in which a Morgan Stanley affiliate is a member of a syndicate or selling group, as a result of which an affiliate might benefit from the purchase through receipt of a fee or otherwise. Neither the investment adviser nor any investment sub-adviser will purchase securities on behalf of a Fund from an affiliate that is acting as a manager of a syndicate or selling group. Purchases by the investment adviser on behalf of a Fund from an affiliate acting as a placement agent must meet the requirements of applicable law. Furthermore, Morgan Stanley may face conflicts of interest when the Funds use service providers affiliated with Morgan Stanley because Morgan Stanley receives greater overall fees when they are used.

Eaton Vance National Municipal Opportunities Trust 41 SAI dated July 22, 2021

General Process for Potential Conflicts. All of the transactions described above involve the potential for conflicts of interest between the investment adviser, related persons of the investment adviser and/or their clients. The Advisers Act, the 1940 Act and ERISA impose certain requirements designed to decrease the possibility of conflicts of interest between an investment adviser and its clients. In some cases, transactions may be permitted subject to fulfillment of certain conditions. Certain other transactions may be prohibited. In addition, the investment adviser has instituted policies and procedures designed to prevent conflicts of interest from arising and, when they do arise, to ensure that it effects transactions for clients in a manner that is consistent with its fiduciary duty to its clients and in accordance with applicable law. The investment adviser seeks to ensure that potential or actual conflicts of interest are appropriately resolved taking into consideration the overriding best interests of the client.

FINANCIAL STATEMENTS

The audited financial statements and the report of the independent registered public accounting firm of the Trust, for the fiscal year ended March 31, 2021, are incorporated herein by reference from the Trust's most recent Annual Report to Common Shareholders filed with the SEC on May 26, 2021 (Accession No. 0001193125-21-173500) on Form N-CSR pursuant to Rule 30b2-1 under the 1940 Act.

Eaton Vance National Municipal Opportunities Trust 42 SAI dated July 22, 2021

APPENDIX A

RATINGS

The ratings indicated herein are believed to be the most recent ratings available at the date of this SAI for the securities listed. Ratings are generally given to securities at the time of issuance. While the rating agencies may from time to time revise such ratings, they undertake no obligation to do so, and the ratings indicated do not necessarily represent ratings which would be given to these securities on a particular date.

MOODY'S INVESTORS SERVICE, INC. ('Moody's')

Ratings assigned on Moody's global long-term and short-term rating scales are forward-looking opinions of the relative credit risks of financial obligations issued by non-financial corporates, financial institutions, structured finance vehicles, project finance vehicles, and public sector entities. Long-term ratings are assigned to issuers or obligations with an original maturity of one year or more and reflect both the likelihood of a default or impairment on contractual financial obligations and the expected financial loss suffered in the event of default or impairment. Short-term ratings are assigned to obligations with an original maturity of thirteen months or less and reflect the likelihood of a default or impairment on contractual financial obligations and the expected financial loss suffered in the event of a default or impairment.

GLOBAL LONG-TERM RATINGS SCALE

Aaa: Obligations rated Aaa are judged to be of the highest quality, subject to the lowest level of credit risk.

Aa: Obligations rated Aa are judged to be of high quality and are subject to very low credit risk.

A: Obligations rated A are considered upper-medium grade and are subject to low credit risk.

Baa: Obligations rated Baa are judged to be medium-grade and subject to moderate credit risk and as such may possess certain speculative characteristics

Ba: Obligations rated Ba are judged to be speculative and are subject to substantial credit risk.

B: Obligations rated B are considered speculative and are subject to high credit risk.

Caa: Obligations rated Caa are judged to be speculative of poor standing and are subject to very high credit risk.

Ca: Obligations rated Ca are highly speculative and are likely in, or very near, default, with some prospect of recovery of principal and interest.

C: Obligations rated C are the lowest rated and are typically in default, with little prospect for recovery of principal or interest.

Note: Moody's appends numerical modifiers, 1, 2, and 3 to each generic rating classification from Aa through Caa. The modifier 1 indicates that the obligation ranks in the higher end of its generic rating category; the modifier 2 indicates a mid-range ranking; and the modifier 3 indicates a ranking in the lower end of that generic rating category.

GLOBAL SHORT-TERM RATING SCALE

Moody's short-term ratings are opinions of the ability of issuers to honor short-term financial obligations. Ratings may be assigned to issuers, short-term programs or to individual short-term debt instruments. Such obligations generally have an original maturity not exceeding thirteen months, unless explicitly noted.

P-1: Issuers (or supporting institutions) rated Prime-1 have a superior ability to repay short-term debt obligations.

P-2: Issuers (or supporting institutions) rated Prime-2 have a strong ability to repay short-term debt obligations.

P-3: Issuers (or supporting institutions) rated Prime-3 have an acceptable ability to repay short-term obligations.

NP: Issuers (or supporting institutions) rated Not Prime do not fall within any of the Prime ratings categories.

Eaton Vance National Municipal Opportunities Trust 43 SAI dated July 22, 2021

ISSUER RATINGS

Issuer Ratings are opinions of the ability of entities to honor senior unsecured debt and debt like obligations. As such, Issuer Ratings incorporate any external support that is expected to apply to all current and future issuance of senior unsecured financial obligations and contracts, such as explicit support stemming from a guarantee of all senior unsecured financial obligations and contracts, and/or implicit support for issuers subject to joint default analysis (e.g. banks and government-related issuers). Issuer Ratings do not incorporate support arrangements, such as guarantees, that apply only to specific (but not to all) senior unsecured financial obligations and contracts.

US MUNICIPAL SHORT-TERM OBLIGATION RATINGS AND DEMAND OBLIGATION RATINGS

SHORT-TERM OBLIGATION RATINGS

The global short-term 'prime' rating scale is applied to commercial paper issued by U.S. municipalities and nonprofits. These commercial paper programs may be backed by external letters of credit or liquidity facilities, or by an issuer's self-liquidity.

For other short-term municipal obligations, Moody's uses one of two other short-term rating scales, the Municipal Investment Grade (MIG) and Variable Municipal Investment Grade (VMIG) scales discussed below.

The MIG scale is used for U.S. municipal cash flow notes, bond anticipation notes and certain other short-term obligations, which typically mature in three years or less. Under certain circumstances, the MIG scale is used for bond anticipation notes with maturities of up to five years.

MIG 1 This designation denotes superior credit quality. Excellent protection is afforded by established cash flows, highly reliable liquidity support, or demonstrated broad-based access to the market for refinancing.

MIG 2 This designation denotes strong credit quality. Margins of protection are ample, although not as large as in the preceding group.

MIG 3 This designation denotes acceptable credit quality. Liquidity and cash-flow protection may be narrow, and market access for refinancing is likely to be less well-established.

SG This designation denotes speculative-grade credit quality. Debt instruments in this category may lack sufficient margins of protection.

Demand Obligation Ratings

In the case of variable rate demand obligations (VRDOs), a two-component rating is assigned. The components are a long-term rating and a short-term demand obligation rating. The long-term rating addresses the issuer's ability to meet scheduled principal and interest payments. The short-term demand obligation rating addresses the ability of the issuer or the liquidity provider to make payments associated with the purchase-price-upon demand feature ('demand feature') of the VRDO. The short-term demand obligation rating uses the VMIG scale. VMIG ratings with liquidity support use as an input the short-term counterparty risk assessment of the support provider, or the long-term rating of the underlying obligor in the absence of third party liquidity support. Transitions of VMIG ratings of demand obligations with conditional liquidity support differ from transitions on the Prime scale to reflect the risk that external liquidity support will terminate if the issuer's long-term rating drops below investment grade.

VMIG 1: This designation denotes superior credit quality. Excellent protection is afforded by the superior short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

VMIG 2: This designation denotes strong credit quality. Good protection is afforded by the strong short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

VMIG 3: This designation denotes acceptable credit quality. Adequate protection is afforded by the satisfactory short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

Eaton Vance National Municipal Opportunities Trust 44 SAI dated July 22, 2021

SG: This designation denotes speculative-grade credit quality. Demand features rated in this category may be supported by a liquidity provider that does not have a sufficiently strong short-term rating or may lack the structural or legal protections necessary to ensure the timely payment of purchase price upon demand.

S&P GLOBAL RATINGS ('S&P')

ISSUE CREDIT RATINGS DEFINITIONS

An S&P issue credit rating is a forward-looking opinion about the creditworthiness of an obligor with respect to a specific financial obligation, a specific class of financial obligations, or a specific financial program (including ratings on medium-term note programs and commercial paper programs). It takes into consideration the creditworthiness of guarantors, insurers, or other forms of credit enhancement on the obligation and takes into account the currency in which the obligation is denominated. The opinion reflects S&P's view of the obligor's capacity and willingness to meet its financial commitments as they come due, and may assess terms, such as collateral security and subordination, which could affect ultimate payment in the event of default.

Issue credit ratings can be either long-term or short-term. Short-term issue credit ratings are generally assigned to those obligations considered short-term in the relevant market. Short-term issue credit ratings are also used to indicate the creditworthiness of an obligor with respect to put features on long-term obligations. Medium-term notes are assigned long-term ratings.

LONG-TERM ISSUE CREDIT RATINGS:

Issue credit ratings are based, in varying degrees, on S&P's analysis of the following considerations:

· Likelihood of payment-capacity and willingness of the obligor to meet its financial commitment on an obligation in accordance with the terms of the obligation;

· Nature of and provisions of the financial obligation and the promise that it is imputed; and

· Protection afforded by, and relative position of, the financial obligation in the event of bankruptcy, reorganization, or other arrangement under the laws of bankruptcy and other laws affecting creditors' rights.

Issue ratings are an assessment of default risk, but may incorporate an assessment of relative seniority or ultimate recovery in the event of default. Junior obligations are typically rated lower than senior obligations, to reflect the lower priority in bankruptcy, as noted above. (Such differentiation may apply when an entity has both senior and subordinated obligations, secured and unsecured obligations, or operating company and holding company obligations.)

AAA: An obligation rated 'AAA' has the highest rating assigned by S&P. The obligor's capacity to meet its financial commitment on the obligation is extremely strong.

AA: An obligation rated 'AA' differs from the highest-rated obligors only to a small degree. The obligor's capacity to meet its financial commitments on the obligation is very strong.

A: An obligation rated 'A' is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher-rated categories. However, the obligor's capacity to meet its financial commitments on the obligation is still strong.

BBB: An obligation rated 'BBB' exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to weaken the obligor's capacity to meet its financial commitments on the obligation.

BB, B, CCC, CC and C

Obligations rated 'BB', 'B', 'CCC', 'CC', and 'C' are regarded as having significant speculative characteristics. 'BB' indicates the least degree of speculation and 'C' the highest. While such obligations will likely have some quality and protective characteristics, these may be outweighed by large uncertainties or major exposures to adverse conditions.

BB: An obligation rated 'BB' is less vulnerable to non-payment than other speculative issues. However, it faces major ongoing uncertainties or exposure to adverse business, financial, or economic conditions that could lead to the obligor's inadequate capacity to meet its financial commitment on the obligation.

Eaton Vance National Municipal Opportunities Trust 45 SAI dated July 22, 2021

B: An obligation rated 'B' is more vulnerable to nonpayment than obligations rated 'BB', but the obligor currently has the capacity to meet its financial commitment on the obligation. Adverse business, financial or economic conditions will likely impair the obligor's capacity or willingness to meet its financial commitment on the obligation.

CCC: An obligation rated 'CCC' is currently vulnerable to nonpayment, and is dependent upon favorable business, financial, and economic conditions for the obligor to meet its financial commitments on the obligation. In the event of adverse business, financial or, economic conditions, the obligor is not likely to have the capacity to meet its financial commitment on the obligation.

CC: An obligation rated 'CC' is currently highly vulnerable to nonpayment. The 'CC' rating is used when a default has not yet occurred, but S&P expects default to be a virtual certainty, regardless of the anticipated time to default.

C: An obligation rated 'C' is currently highly vulnerable to nonpayment, and the obligation is expected to have lower relative seniority or lower ultimate recovery compared to obligations that are rated higher.

D: An obligation rated 'D' is in default or in breach of an imputed promise. For non-hybrid capital instruments, the 'D' rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within five business days in the absence of a stated grace period or within the earlier of the stated grace period or 30 calendar days. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. An obligation's rating is lowered to 'D' if it is subject to a distressed exchange offer.

NR: This indicates that a rating has not been assigned or is no longer assigned.

Plus (+) or Minus (-): The ratings from 'AA' to' CCC' may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

SHORT-TERM ISSUE CREDIT RATINGS

A-1: A short-term obligation rated 'A-1' is rated in the highest category by S&P. The obligor's capacity to meet its financial commitment on the obligation is strong. Within this category, certain obligations are designated with a plus sign (+). This indicates that the obligor's capacity to meet its financial commitments on the obligation is extremely strong.

A-2: A short-term obligation rated 'A-2' is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher rating categories. However, the obligor's capacity to meet its financial commitment on the obligation is satisfactory.

A-3: A short-term obligation rated 'A-3' exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to weaken an obligor's capacity to meet its financial commitment on the obligation.

B: A short-term obligation rated 'B' is regarded as vulnerable and has significant speculative characteristics. The obligor currently has the capacity to meet its financial commitments; however, it faces major ongoing uncertainties which could lead to the obligor's inadequate capacity to meet its financial commitments.

C: A short-term obligation rated 'C' is currently vulnerable to nonpayment and is dependent upon favorable business, financial and economic conditions for the obligor to meet its financial commitments on the obligation.

D: A short-term obligation rated 'D' is in default or in breach of an imputed promise. For non-hybrid capital instruments, the 'D' rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within any stated grace period. However, any stated grace period longer than five business days will be treated as five business days. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of a similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. A rating on an obligation is lowered to 'D' if it is subject to a distressed exchange offer.

ISSUER CREDIT RATINGS DEFINITIONS

S&P's issuer credit rating is a forward-looking opinion about an obligor's overall creditworthiness. This opinion focuses on the obligor's capacity and willingness to meet its financial commitments as they come due. It does not apply to any specific financial obligation, as it does not take into account the nature of and provisions of the obligation, its standing in bankruptcy or liquidation, statutory preferences, or the legality and enforceability of the obligation.

Eaton Vance National Municipal Opportunities Trust 46 SAI dated July 22, 2021

Sovereign credit ratings are forms of issuer credit ratings.

Issuer credit ratings can be either long-term or short-term.

LONG-TERM ISSUER CREDIT RATINGS

AAA: An obligor rated 'AAA' has extremely strong capacity to meet its financial commitments. 'AAA' is the highest issuer credit rating assigned by S&P.

AA: An obligor rated 'AA' has very strong capacity to meet its financial commitments. It differs from the highest-rated obligors only to a small degree.

A: An obligor rated 'A' has strong capacity to meet its financial commitments but is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligors in higher-rated categories.

BBB: An obligor rated 'BBB' has adequate capacity to meet its financial commitments. However, adverse economic conditions or changing circumstances are more likely to weaken the obligor's capacity to meet its financial commitments.

BB, B, CCC and CC

Obligors rated 'BB', 'B', 'CCC', and 'CC' are regarded as having significant speculative characteristics. 'BB' indicates the least degree of speculation and 'CC' the highest. While such obligors will likely have some quality and protective characteristics, these may be outweighed by large uncertainties or major exposure to adverse conditions.

BB: An obligor 'BB' is less vulnerable in the near term than other lower-rated obligors. However, it faces major ongoing uncertainties and exposure to adverse business, financial, or economic conditions that could lead to the obligor's inadequate capacity to meet its financial commitments.

B: An obligor rated 'B' is more vulnerable than the obligors rated 'BB', but the obligor currently has the capacity to meet its financial commitments. Adverse business, financial, or economic conditions will likely impair the obligor's capacity or willingness to meets its financial commitments.

CCC: An obligor rated 'CCC' is currently vulnerable, and is dependent upon favorable business, financial, and economic conditions to meet its financial commitments.

CC: An obligor rated 'CC' is currently highly vulnerable. The 'CC' rating is used when a default has not yet occurred, but S&P expects default to be a virtual certainty, regardless of the anticipated time to default.

SD and D: An obligor is rated 'SD' (selective default) or 'D' if S&P considers there to be a default on one or more of its financial obligations, whether long -or short-term, including rated and unrated financial obligations but excluding hybrid instruments classified as regulatory capital or in non-payment according to terms. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay all or substantially all of its obligations as they come due. An 'SD' rating is assigned when S&P believes that the obligor has selectively defaulted on a specific issue or class of obligations but it will continue to meet its payment obligations on other issues or classes of obligations in a timely manner. A rating on an obligor is lowered to 'D' or 'SD' if it is conducting a distressed exchange offer.

NR: Indicates that a rating has not been assigned or is no longer assigned.

Plus (+) or Minus (-): The ratings from 'AA' to' CCC' may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

SHORT-TERM ISSUER CREDIT RATINGS

A-1: An obligor rated 'A-1' has strong capacity to meet its financial commitments. It is rated in the highest category by S&P. Within this category, certain obligors are designated with a plus sign (+). This indicates that the obligor's capacity to meet its financial commitments is extremely strong.

Eaton Vance National Municipal Opportunities Trust 47 SAI dated July 22, 2021

A-2: An obligor rated 'A-2' has satisfactory capacity to meet its financial commitments. However, it is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligors in the highest rating category.

A-3: An obligor rated 'A-3' has adequate capacity to meet its financial obligations. However, adverse economic conditions or changing circumstances are more likely to weaken the obligor's capacity to meet its financial commitments.

B: An obligor rated 'B' is regarded as vulnerable and has significant speculative characteristics. The obligor currently has the capacity to meet its financial commitments; however, it faces major ongoing uncertainties which could lead to the obligor's inadequate capacity to meet its financial commitments.

C: An obligor rated 'C' is currently vulnerable to nonpayment that would result in a 'SD' or 'D' issuer rating, and is dependent upon favorable business, financial, and economic conditions for it to meet its financial commitments.

SD and D: An obligor is rated 'SD' (selective default) or 'D' if S&P considers there to be a default on one or more of its financial obligations, whether long- or short-term, including rated and unrated obligations but excluding hybrid instruments classified as regulatory capital or in nonpayment according to term. An obligor is considered in default unless S&P believes that such payments will be made within any stated grace period. However, any stated grace period longer than five business days will be treated as five business days. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay all or substantially all of its obligations as they come due. An 'SD' rating is assigned when S&P believes that the obligor has selectively defaulted on a specific issue or class of obligations, excluding hybrid instruments classified as regulatory capital, but it will continue to meet its payment obligations on other issues or classes of obligations in a timely manner. An obligor's rating is lowered to 'D' or 'SD' if it is conducting a distressed exchange offer.

NR: Indicates that a rating has not been assigned or is no longer assigned.

MUNICIPAL SHORT-TERM NOTE RATINGS

SHORT-TERM NOTES: An S&P U.S. municipal note rating reflects S&P opinions about the liquidity factors and market access risks unique to notes. Notes due in three years or less will likely receive a note rating. Notes with an original maturity of more than three years will most likely receive a long-term debt rating. In determining which type of rating, if any, to assign, S&P's analysis will review the following considerations: Amortization schedule--the larger the final maturity relative to other maturities, the more likely it will be treated as a note; and Source of payment--the more dependent the issue is on the market for its refinancing, the more likely it will be treated as a note.

Municipal Short-Term Note rating symbols are as follows:

SP-1: Strong capacity to pay principal and interest. An issue determined to possess a very strong capacity to pay debt will be given a plus (+) designation.

SP-2: Satisfactory capacity to pay principal and interest, with some vulnerability to adverse financial and economic changes over the term of the notes.

SP-3: Speculative capacity to pay principal and interest.

D: 'D' is assigned upon failure to pay the note when due, completion of a distressed exchange offer, or the filing of a bankruptcy petition or the taking of similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions.

FITCH RATINGS

LONG-TERM CREDIT RATINGS

Issuer Default Ratings

AAA: Highest credit quality. 'AAA' ratings denote the lowest expectation of default risk. They are assigned only in case of exceptionally strong capacity for payment of financial commitments. The capacity is highly unlikely to be adversely affected by foreseeable events.

Eaton Vance National Municipal Opportunities Trust 48 SAI dated July 22, 2021

AA: Very high credit quality. 'AA' ratings denote expectations of very low default risk. They indicate very strong capacity for payment of financial commitments. This capacity is not significantly vulnerable to foreseeable events.

A: High credit quality. 'A' ratings denote expectations of low default risk. The capacity for payment of financial commitments is considered strong. The capacity may, nevertheless, be more vulnerable to changes in circumstances or in economic conditions than is the case for higher ratings.

BBB: Good credit quality. 'BBB' ratings indicate that expectations of default risk are currently low. The capacity for payment of financial commitments is considered adequate but adverse business or economic conditions are more likely to impair this capacity.

BB: Speculative. 'BB' ratings indicate an elevated vulnerability to default risk, particularly in the event of adverse changes in business or economic conditions over time; however, business or financial flexibility exist that supports the servicing of financial commitments.

B: Highly speculative. B' ratings indicate that material default risk is present, but a limited margin of safety remains. Financial commitments are currently being met; however, capacity for continued payment is vulnerable to deterioration in the business and economic environment.

CCC: Substantial credit risk. Default is a real possibility.

CC: Very high levels of credit risk. Default of some kind appears probable.

C: Near default. A default or default-like process has begun, or the issuer is in standstill, or for a closed funding vehicle, payment capacity is irrevocably impaired. Conditions that are indicative of a 'C' category rating for an issuer include:

• The issuer has entered into a grace or cure period following non-payment of a material financial obligation;

• The issuer had entered into a temporary negotiated waiver or standstill agreement following a payment default on a material financial obligation;

• The formal announcement by the issuer or their agent of distressed debt exchange;

• A closed financing vehicle where payment capacity is irrevocably impaired such that it is not expected to pay interest and/or principal in full during the life of the transaction, but where no payment default is imminent.

RD: Restricted Default. 'RD' ratings indicate an issuer that in Fitch's opinion has experienced:

• An unsecured payment default or distressed debt exchange on a bond, loan or other material financial obligation, but

• Has not entered into bankruptcy filings, administration, receivership, liquidation, or other formal winding-up procedure, and

• Has not otherwise ceased operating.

This would include:

• The selective payment default on specific class or currency of debt;

• The uncured expiry of any applicable grace period, cure period or default forbearance period following a payment default on a bank loan, capital markets security or other material financial obligation;

• The extension of multiple waivers of forbearance periods upon a payment default on one or more material financial obligations, either in series or in parallel; ordinary execution of a distressed debt exchange on one or more material financial obligations.

D: Default. 'D' ratings indicate an issuer that in Fitch's opinion has entered into bankruptcy filings, administration, receivership, liquidation or other formal winding-up procedure or that has otherwise ceased business.

Eaton Vance National Municipal Opportunities Trust 49 SAI dated July 22, 2021

• Default ratings are not assigned prospectively to entities or their obligations; within this context, non-payment on an instrument that contains a deferral feature or grace period will generally not be considered a default until after the expiration of the deferral or grace period, unless a default is otherwise driven by bankruptcy or other similar circumstance, or by a distressed debt exchange.

• In all cases, the assignment of default rating reflects the agency's opinion as to the most appropriate rating category consistent with the rest of its universe of ratings and may differ from the definition of default under the terms of an issuer's financial obligations or local commercial practice.

Notes to Long-Term ratings:

The modifiers '+' or '-' may be appended to a rating to denote relative status within major rating categories. Such suffixes are not added to the 'AAA' Long-Term IDR category, or to Long-Term IDR categories below 'B'.

Short-Term Credit Ratings Assigned to Issuers and Obligations

A short-term issuer or obligation rating is based in all cases on the short-term vulnerability to default of the rated entity and relates to the capacity to meet financial obligations in accordance with the documentation governing the relevant obligation. Short-Term Ratings are assigned to obligations whose initial maturity is viewed as 'short term' based on market convention. Typically, this means up to 13 months for corporate, sovereign, and structured obligations, and up to 36 months for obligations in U.S. public finance markets.

F1: Highest short-term credit quality. Indicates the strongest intrinsic capacity for timely payment of financial commitments; may have an added '+' to denote any exceptionally strong credit feature.

F2: Good short-term credit quality. Good intrinsic capacity for timely payment of financial commitments.

F3: Fair short-term credit quality. The intrinsic capacity for timely payment of financial commitments is adequate.

B: Speculative short-term credit quality. Minimal capacity for timely payment of financial commitments, plus heightened vulnerability to near term adverse changes in financial and economic conditions.

C: High short-term default risk. Default is a real possibility.

RD: Restricted default. Indicates an entity that has defaulted on one or more of its financial commitments, although it continues to meet other financial obligations. Typically applicable to entity ratings only.

D: Indicates a broad-based default event for an entity, or the default of a short-term obligation.

DESCRIPTION OF INSURANCE FINANCIAL STRENGTH RATINGS

Moody's Investors Service, Inc. Insurance Financial Strength Ratings

Moody's Insurance Financial Strength Ratings are opinions of the ability of insurance companies to repay punctually senior policyholder claims and obligations and also reflect the expected financial loss suffered in the event of default.

S&P Insurer Financial Strength Ratings

An S&P insurer financial strength rating is a forward-looking opinion about the financial security characteristics of an insurance organization with respect to its ability to pay under its insurance policies and contracts in accordance with their terms. Insurer financial strength ratings are also assigned to health maintenance organizations and similar health plans with respect to their ability to pay under their policies and contracts in accordance with their terms.

This opinion is not specific to any particular policy or contract, nor does it address the suitability of a particular policy or contract for a specific purpose or purchaser. Furthermore, the opinion does not take into account deductibles, surrender or cancellation penalties, timeliness of payment, nor the likelihood of the use of a defense such as fraud to deny claims.

Insurer financial strength ratings do not refer to an organization's ability to meet nonpolicy (i.e., debt) obligations. Assignment of ratings to debt issued by insurers or to debt issues that are fully or partially supported by insurance policies, contracts, or guarantees is a separate process from the determination of insurer financial strength ratings, and it follows procedures consistent with those used to assign an issue credit rating. An insurer financial strength rating is not a recommendation to purchase or discontinue any policy or contract issued by an insurer.

Eaton Vance National Municipal Opportunities Trust 50 SAI dated July 22, 2021

Long-Term Insurer Financial Strength Ratings

Category Definition

AAA

An insurer rated 'AAA' has extremely strong financial security characteristics. 'AAA' is the highest insurer financial strength rating assigned by S&P.

AA

An insurer rated 'AA' has very strong financial security characteristics, differing only slightly from those rated higher.

A

An insurer rated 'A' has strong financial security characteristics, but is somewhat more likely to be affected by adverse business conditions than are insurers with higher ratings.

BBB

An insurer rated 'BBB' has good financial security characteristics, but is more likely to be affected by adverse business conditions than are higher-rated insurers.

BB, B, CCC and CC

An insurer rated 'BB' or lower is regarded as having vulnerable characteristics that may outweigh its strengths. 'BB' indicates the least degree of vulnerability within the range and 'CC' the highest.

BB

An insurer rated 'BB' has marginal financial security characteristics. Positive attributes exist, but adverse business conditions could lead to insufficient ability to meet financial commitments.

B

An insurer rated 'B' has weak financial security characteristics. Adverse business conditions will likely impair its ability to meet financial commitments.

CCC

An insurer rated 'CCC' has very weak financial security characteristics, and is dependent on favorable business conditions to meet financial commitments.

CC

An insurer rated 'CC' has extremely weak financial security characteristics and is likely not to meet some of its financial commitments.

SD or D

An insurer rated 'SD' (selective default) or 'D' is in default on one or more of its insurance policy obligations. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of similar action if payments on a policy obligation are at risk. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay substantially all of its obligations in full in accordance with the policy terms. An 'SD' rating is assigned when S&P believes that the insurer has selectively defaulted on a specific class of policies but it will continue to meet its payment obligations on other classes of obligations. A selective default includes the completion of a distressed exchange offer. Claim denials due to lack of coverage or other legally permitted defenses are not considered defaults.

NR: Indicates that a rating has not been assigned or is no longer assigned.

Plus (+) or Minus (-): The ratings from 'AA' to' CCC' may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

Eaton Vance National Municipal Opportunities Trust 51 SAI dated July 22, 2021

Fitch Insurer Financial Strength Rating

The Insurer Financial Strength (IFS) Rating provides an assessment of the financial strength of an insurance organization. The IFS Rating is assigned to the insurance company's policyholder obligations, including assumed reinsurance obligations and contract holder obligations, such as guaranteed investment contracts. The IFS Rating reflects both the ability of the insurer to meet these obligations on a timely basis, and expected recoveries received by claimants in the event the insurer stops making payments or payments are interrupted, due to either the failure of the insurer or some form of regulatory intervention. In the context of the IFS Rating, the timeliness of payments is considered relative to both contract and/or policy terms but also recognizes the possibility of reasonable delays caused by circumstances common to the insurance industry, including claims reviews, fraud investigations and coverage disputes.

The IFS Rating does not encompass policyholder obligations residing in separate accounts, unit-linked products or segregated funds, for which the policyholder bears investment or other risks. However, any guarantees provided to the policyholder with respect to such obligations are included in the IFS Rating.

Expected recoveries are based on the agency's assessments of the sufficiency of an insurance company's assets to fund policyholder obligations, in a scenario in which payments have ceased or been interrupted. Accordingly, expected recoveries exclude the impact of recoveries obtained from any government sponsored guaranty or policyholder protection funds. Expected recoveries also exclude the impact of collateralization or security, such as letters of credit or trusteed assets, supporting select reinsurance obligations.

IFS Ratings can be assigned to insurance and reinsurance companies in any insurance sector, including the life & annuity, non-life, property/casualty, health, mortgage, financial guaranty, residual value and title insurance sectors, as well as to managed care companies such as health maintenance organizations.

The IFS Rating uses the same symbols used by the agency for its International and National credit ratings of long-term or short-term debt issues. However, the definitions associated with the ratings reflect the unique aspects of the IFS Rating within an insurance industry context.

Obligations for which a payment interruption has occurred due to either the insolvency or failure of the insurer or some form of regulatory intervention will generally be rated between 'B' and 'C' on the Long-Term IFS Rating scales (both International and National). International Short-Term IFS Ratings assigned under the same circumstances will align with the insurer's International Long-Term IFS Ratings.

Eaton Vance National Municipal Opportunities Trust 52 SAI dated July 22, 2021

APPENDIX B

Eaton Vance Funds

Proxy Voting Policy and Procedures

I.   Overview

The Boards of Trustees (the 'Board') of the Eaton Vance Funds1 have determined that it is in the interests of the Funds' shareholders to adopt these written proxy voting policy and procedures (the 'Policy'). For purposes of this Policy:

· 'Fund' means each registered investment company sponsored by the Eaton Vance organization; and
· 'Adviser' means the adviser or sub-adviser responsible for the day-to-day management of all or a portion of the Fund's assets.

II.   Delegation of Proxy Voting Responsibilities

The Board hereby delegates to the Adviser responsibility for voting the Fund's proxies as described in this Policy. In this connection, the Adviser is required to provide the Board with a copy of its proxy voting policies and procedures ('Adviser Procedures') and all Fund proxies will be voted in accordance with the Adviser Procedures, provided that in the event a material conflict of interest arises with respect to a proxy to be voted for the Fund (as described in Section IV below) the Adviser shall follow the process for voting such proxy as described in Section IV below.

The Adviser is required to report any material change to the Adviser Procedures to the Board in the manner set forth in Section V below. In addition, the Board will review the Adviser Procedures annually.

III.   Delegation of Proxy Voting Disclosure Responsibilities

Pursuant to Rule 30b1-4 promulgated under the Investment Company Act of 1940, as amended (the '1940 Act'), the Fund is required to file Form N-PX no later than August 31st of each year. On Form N-PX, the Fund is required to disclose, among other things, information concerning proxies relating to the Fund's portfolio investments, whether or not the Fund (or its Adviser) voted the proxies relating to securities held by the Fund and how it voted on the matter and whether it voted for or against management.

To facilitate the filing of Form N-PX for the Fund:

· The Adviser is required to record, compile and transmit in a timely manner all data required to be filed on Form N-PX for the Fund that it manages. Such data shall be transmitted to Eaton Vance Management, which acts as administrator to the Fund (the 'Administrator') or the third party service provider designated by the Administrator; and
· the Administrator is required to file Form N-PX on behalf of the Fund with the Securities and Exchange Commission ('Commission') as required by the 1940 Act. The Administrator may delegate the filing to a third party service party provided each such filing is reviewed and approved by the Administrator.

IV.   Conflicts of Interest

The Board expects the Adviser, as a fiduciary to the Fund it manages, to put the interests of the Fund and its shareholders above those of the Adviser. When required to vote a proxy for the Fund, the Adviser may have material business relationships with the issuer soliciting the proxy that could give rise to a potential material conflict of interest for the Adviser.2 In the event such a material conflict of interest arises, the Adviser, to the extent it is aware or reasonably should have been aware of the material conflict, will refrain from voting any proxies related to companies giving rise to such material conflict until it notifies and consults with the appropriate Board, or any committee, sub-committee or group of Independent Trustees identified by the Board (as long as such committee, sub-committee or group contains at least two or more Independent Trustees) (the 'Board Members'), concerning the material conflict.3 For ease of communicating with the Board Members, the Adviser is required to provide the foregoing notice to the Fund's Chief Legal Officer who will then notify and facilitate a consultation with the Board Members.

Once the Board Members have been notified of the material conflict:

· They shall convene a meeting to review and consider all relevant materials related to the proxies involved. This meeting shall be convened within 3 business days, provided that it an effort will be made to convene the meeting sooner if the proxy must be voted in less than 3 business days;
· In considering such proxies, the Adviser shall make available all materials requested by the Board Members and make reasonably available appropriate personnel to discuss the matter upon request.
Eaton Vance National Municipal Opportunities Trust 53 SAI dated July 22, 2021
· The Board Members will then instruct the Adviser on the appropriate course of action with respect to the proxy at issue.

If the Board Members are unable to meet and the failure to vote a proxy would have a material adverse impact on the Fund(s) involved, the Adviser will have the right to vote such proxy, provided that it discloses the existence of the material conflict to the Chairperson of the Board as soon as practicable and to the Board at its next meeting. Any determination regarding the voting of proxies of the Fund that is made by the Board Members shall be deemed to be a good faith determination regarding the voting of proxies by the full Board.

V.    Reports and Review

The Administrator shall make copies of each Form N-PX filed on behalf of the Fund available for the Boards' review upon the Boards' request. The Administrator (with input from the Adviser for the Fund) shall also provide any reports reasonably requested by the Board regarding the proxy voting records of the Fund.

The Adviser shall report any material changes to the Adviser Procedures to the Board as soon as practicable and the Boards will review the Adviser Procedures annually.

The Adviser also shall report any material changes to the Adviser Procedures to the Fund Chief Legal Officer prior to implementing such changes in order to enable the Administrator to effectively coordinate the Fund's disclosure relating to the Adviser Procedures.

To the extent requested by the Commission, the Policy and the Adviser Procedures shall be appended to the Fund's statement of additional information included in its registration statement.

_____________________
1 The Eaton Vance Funds may be organized as trusts or corporations. For ease of reference, the Funds may be referred to herein as Trusts and the Funds' Board of Trustees or Board of Directors may be referred to collectively herein as the Board.
2 An Adviser is expected to maintain a process for identifying a potential material conflict of interest. As an example only, such potential conflicts may arise when the issuer is a client of the Adviser and generates a significant amount of fees to the Adviser or the issuer is a distributor of the Adviser's products.
3 If a material conflict of interest exists with respect to a particular proxy and the proxy voting procedures of the relevant Adviser require that proxies are to be voted in accordance with the recommendation of a third party proxy voting vendor, the requirements of this Section IV shall only apply if the Adviser intends to vote such proxy in a manner inconsistent with such third party recommendation.
Eaton Vance National Municipal Opportunities Trust 54 SAI dated July 22, 2021

APPENDIX C

EATON VANCE MANAGEMENT

BOSTON MANAGEMENT AND RESEARCH

EATON VANCE WATEROAK ADVISORS

EATON VANCE MANAGEMENT (INTERNATIONAL) LIMITED

EATON VANCE GLOBAL ADVISORS LIMITED

EATON VANCE ADVISERS INTERNATIONAL LTD.

PROXY VOTING POLICIES AND PROCEDURES

I. Introduction

Eaton Vance Management, Boston Management and Research, Eaton Vance WaterOak Advisors, Eaton Vance Management (International) Limited, Eaton Vance Global Advisors Limited and Eaton Vance Advisers International Ltd. (each an 'Adviser' and collectively the 'Advisers') have each adopted and implemented policies and procedures that each Adviser believes are reasonably designed to ensure that proxies are voted in the best interest of clients, in accordance with its fiduciary duties and, to the extent applicable, Rule 206(4)-6 under the Investment Advisers Act of 1940, as amended. The Advisers' authority to vote the proxies of their clients is established by their advisory contracts or similar documentation. These proxy policies and procedures are intended to reflect current requirements applicable to investment advisers registered with the U.S. Securities and Exchange Commission ('SEC'). These procedures may change from time to time.

II. Overview

Each Adviser manages its clients' assets with the overriding goal of seeking to provide the greatest possible return to such clients consistent with governing laws and the investment policies of each client. In pursuing that goal, each Adviser seeks to exercise its clients' rights as shareholders of voting securities to support sound corporate governance of the companies issuing those securities with the principle aim of maintaining or enhancing the companies' economic value.

The exercise of shareholder rights is generally done by casting votes by proxy at shareholder meetings on matters submitted to shareholders for approval (for example, the election of directors or the approval of a company's stock option plans for directors, officers or employees). Each Adviser has established guidelines ('Guidelines') as described below and generally will utilize such Guidelines in voting proxies on behalf of its clients. The Guidelines are largely based on those developed by the Agent (defined below) but also reflect input from the Global Proxy Group (defined below) and other Adviser investment professionals and are believed to be consistent with the views of the Adviser on the various types of proxy proposals. These Guidelines are designed to promote accountability of a company's management and board of directors to its shareholders and to align the interests of management with those of shareholders. The Guidelines provide a framework for analysis and decision making but do not address all potential issues.

Except as noted below, each Adviser will vote any proxies received by a client for which it has sole investment discretion through a third-party proxy voting service ('Agent') in accordance with the Guidelines in a manner that is reasonably designed to eliminate any potential conflicts of interest, as described more fully below. The Agent is currently Institutional Shareholder Services Inc. Where applicable, proxies will be voted in accordance with client-specific guidelines or, in the case of an Eaton Vance Fund that is sub-advised, pursuant to the sub-adviser's proxy voting policies and procedures. Although an Adviser retains the services of the Agent for research and voting recommendations, the Adviser remains responsible for proxy voting decisions.

III. Roles and Responsibilities

A. Proxy Administrator

The Proxy Administrator and/or her designee coordinate the consideration of proxies referred back to the Adviser by the Agent, and otherwise administers these Procedures. In the Proxy Administrator's absence, another employee of the Adviser may perform the Proxy Administrator's responsibilities as deemed appropriate by the Global Proxy Group. The Proxy Administrator also may designate another employee to perform certain of the Proxy Administrator's duties hereunder, subject to the oversight of the Proxy Administrator.

Eaton Vance National Municipal Opportunities Trust 55 SAI dated July 22, 2021

B. Agent

The Agent is responsible for coordinating with the clients' custodians and the Advisers to ensure that all proxy materials received by the custodians relating to the portfolio securities are processed in a timely fashion. Each Adviser shall instruct the custodian for its clients to deliver proxy ballots and related materials to the Agent. The Agent shall vote and/or refer all proxies in accordance with the Guidelines. The Agent shall retain a record of all proxy votes handled by the Agent. With respect to each Eaton Vance Fund memorialized therein, such record must reflect all of the information required to be disclosed in the Fund's Form N-PX pursuant to Rule 30b1-4 under the Investment Company Act of 1940, to the extent applicable. In addition, the Agent is responsible for maintaining copies of all proxy statements received by issuers and to promptly provide such materials to an Adviser upon request.

Subject to the oversight of the Advisers, the Agent shall establish and maintain adequate internal controls and policies in connection with the provision of proxy voting services to the Advisers, including methods to reasonably ensure that its analysis and recommendations are not influenced by a conflict of interest, and shall disclose such controls and policies to the Advisers when and as provided for herein. Unless otherwise specified, references herein to recommendations of the Agent shall refer to those in which no conflict of interest has been identified. The Advisers are responsible for the ongoing oversight of the Agent as contemplated by SEC Staff Legal Bulletin No. 20 (June 30, 2014) and interpretive guidance issued by the SEC in August 2019 regarding proxy voting responsibilities of investment advisers (Release Nos. IA-5325 and IC-33605). Such oversight currently may include one or more of the following and may change from time to time:

·periodic review of Agent's proxy voting platform and reporting capabilities (including recordkeeping);

·periodic review of a sample of ballots for accuracy and correct application of the Guidelines;

·periodic meetings with Agent's client services team;

·periodic in-person and/or web-based due diligence meetings;

·receipt and review of annual certifications received from the Agent;

·annual review of due diligence materials provided by the Agent, including review of procedures and practices regarding potential conflicts of interests;

·periodic review of relevant changes to Agent's business; and/or

· periodic review of the following to the extent not included in due diligence materials provided by the Agent: (i) Agent's staffing, personnel and/or technology; (ii) Agent's process for seeking timely input from issuers (e.g., with respect to proxy voting policies, methodologies and peer group construction); (iii) Agent's process for use of third-party information; (iv) the Agent's policies and procedures for obtaining current and accurate information relevant to matters in its research and on which it makes voting recommendations; and (v) Agent's business continuity program ('BCP') and any service/operational issues experienced due to the enacting of Agent's BCP.

C. Global Proxy Group

The Adviser shall establish a Global Proxy Group which is responsible for establishing the Guidelines (described below) and reviewing such Guidelines at least annually. The Global Proxy Group shall also review recommendations to vote proxies in a manner that is contrary to the Guidelines and when the proxy relates to a conflicted company of the Adviser or the Agent as described below.

The members of the Global Proxy Group shall include the Chief Equity Investment Officer of Eaton Vance Management ('EVM') and selected members of the Equity Departments of EVM and Eaton Vance Advisers International Ltd. ('EVAIL') and EVM's Global Income Department. The Proxy Administrator is not a voting member of the Global Proxy Group. Members of the Global Proxy Group may be changed from time to time at the Advisers' discretion. Matters that require the approval of the Global Proxy Group may be acted upon by its member(s) available to consider the matter.

IV. Proxy Voting

A. The Guidelines

The Global Proxy Group shall establish recommendations for the manner in which proxy proposals shall be voted (the 'Guidelines'). The Guidelines shall identify when ballots for specific types of proxy proposals shall be voted(1) or referred to the Adviser. The Guidelines shall address a wide variety of individual topics, including, among other matters, shareholder voting rights, anti-takeover defenses, board structures, the election of directors, executive and director compensation, reorganizations, mergers, issues of corporate social responsibility and other proposals affecting shareholder rights. In determining the Guidelines, the Global Proxy Group considers the recommendations of the Agent as well as input from the Advisers' portfolio managers and analysts and/or other internally developed or third party research.

Eaton Vance National Municipal Opportunities Trust 56 SAI dated July 22, 2021

The Global Proxy Group shall review the Guidelines at least annually and, in connection with proxies to be voted on behalf of the Eaton Vance Funds, the Adviser will submit amendments to the Guidelines to the Fund Boards each year for approval.

With respect to the types of proxy proposals listed below, the Guidelines will generally provide as follows:

1. Proposals Regarding Mergers and Corporate Restructurings/Disposition of Assets/Termination/Liquidation and Mergers

The Agent shall be directed to refer proxy proposals accompanied by its written analysis and voting recommendation to the Proxy Administrator and/or her designee for all proposals relating to Mergers and Corporate Restructurings.

2. Corporate Structure Matters/Anti-Takeover Defenses

As a general matter, the Advisers will normally vote against anti-takeover measures and other proposals designed to limit the ability of shareholders to act on possible transactions (except in the case of closed-end management investment companies).

3. Proposals Regarding Proxy Contests

The Agent shall be directed to refer contested proxy proposals accompanied by its written analysis and voting recommendation to the Proxy Administrator and/or her designee.

4. Social and Environmental Issues

The Advisers will vote social and environmental proposals on a 'case-by-case' basis taking into consideration industry best practices and existing management policies and practices.

Interpretation and application of the Guidelines is not intended to supersede any law, regulation, binding agreement or other legal requirement to which an issuer or the Adviser may be or become subject. The Guidelines generally relate to the types of proposals that are most frequently presented in proxy statements to shareholders. In certain circumstances, an Adviser may determine to vote contrary to the Guidelines subject to the voting procedures set forth below.

B. Voting Procedures

Except as noted in Section V below, the Proxy Administrator and/or her designee shall instruct the Agent to vote proxies as follows:

1. Vote in Accordance with Guidelines

If the Guidelines prescribe the manner in which the proxy is to be voted, the Agent shall vote in accordance with the Guidelines, which for certain types of proposals, are recommendations of the Agent made on a case-by-case basis.

2. Seek Guidance for a Referred Item or a Proposal for which there is No Guideline

If (i) the Guidelines state that the proxy shall be referred to the Adviser to determine the manner in which it should be voted or (ii) a proxy is received for a proposal for which there is no Guideline, the Proxy Administrator and/or her designee shall consult with the analyst(s) covering the company subject to the proxy proposal and shall instruct the Agent to vote in accordance with the determination of the analyst. The Proxy Administrator and/or her designee will maintain a record of all proxy proposals that are referred by the Agent, as well as all applicable recommendations, analysis and research received and the resolution of the matter. Where more than one analyst covers a particular company and the recommendations of such analysts for voting a proposal subject to this Section IV.B.2 conflict, the Global Proxy Group shall review such recommendations and any other available information related to the proposal and determine the manner in which it should be voted, which may result in different recommendations for clients (including Funds).

3. Votes Contrary to the Guidelines or Where Agent is Conflicted

In the event an analyst with respect to companies within his or her coverage area may recommend a vote contrary to the Guidelines, the Proxy Administrator and/or her designee will provide the Global Proxy Group with the Agent's recommendation for the proposal along with any other relevant materials, including a description of the basis for the analyst's recommendation via email and the Proxy Administrator and/or designee will then instruct the Agent to vote the proxy in the manner determined by the Global Proxy Group. Should the vote by the GlobalProxy Group concerning one or more recommendations result in a tie, EVM's Chief Equity Investment Officer will determine the manner in which the proxy will be voted. The Adviser will provide a report to the Boards of Trustees of the Eaton Vance Funds reflecting any votes cast on behalf of the Eaton Vance Funds contrary to the Guidelines, and shall do so quarterly. A similar process will be followed if the Agent has a conflict of interest with respect to a proxy as described in Section VI.B.

Eaton Vance National Municipal Opportunities Trust 57 SAI dated July 22, 2021

4. Do Not Cast a Vote

It shall generally be the policy of the Advisers to take no action on a proxy for which no client holds a position or otherwise maintains an economic interest in the relevant security at the time the vote is to be cast. In addition, the Advisers may determine not to vote (i) if the economic effect on shareholders' interests or the value of the portfolio holding is indeterminable or insignificant (e.g., proxies in connection with securities no longer held in the portfolio of a client or proxies being considered on behalf of a client that is no longer in existence); (ii) if the cost of voting a proxy outweighs the benefits (e.g., certain international proxies, particularly in cases in which share blocking practices may impose trading restrictions on the relevant portfolio security); or (iii) in markets in which shareholders' rights are limited; and (iv) the Adviser is unable to access or access timely ballots or other proxy information. Non-Votes may also result in certain cases in which the Agent's recommendation has been deemed to be conflicted, as provided for herein.

C. Securities on Loan

When a fund client participates in the lending of its securities and the securities are on loan at the record date for a shareholder meeting, proxies related to such securities generally will not be forwarded to the relevant Adviser by the fund's custodian and therefore will not be voted. In the event that the Adviser determines that the matters involved would have a material effect on the applicable fund's investment in the loaned securities, the Adviser will make reasonable efforts to terminate the loan in time to be able to cast such vote or exercise such consent. The Adviser shall instruct the fund's security lending agent to refrain from lending the full position of any security held by a fund to ensure that the Adviser receives notice of proxy proposals impacting the loaned security.

V. Recordkeeping

The Advisers will maintain records relating to the proxies they vote on behalf of their clients in accordance with Section 204-2 of the Investment Advisers Act of 1940, as amended. Those records will include:

· A copy of the Advisers' proxy voting policies and procedures;
· Proxy statements received regarding client securities. Such proxy statements received from issuers are either in the SEC's EDGAR database or are kept by the Agent and are available upon request;
· A record of each vote cast;
· A copy of any document created by the Advisers that was material to making a decision on how to vote a proxy for a client or that memorializes the basis for such a decision; and
· Each written client request for proxy voting records and the Advisers' written response to any client request (whether written or oral) for such records.

All records described above will be maintained in an easily accessible place for five years and will be maintained in the offices of the Advisers or their Agent for two years after they are created.

Notwithstanding anything contained in this Section V, Eaton Vance Trust Company shall maintain records relating to the proxies it votes on behalf of its clients in accordance with laws and regulations applicable to it and its activities. In addition, EVAIL shall maintain records relating to the proxies it votes on behalf of its clients in accordance with UK law.

VI. Assessment of Agent and Identification and Resolution of Conflicts with Clients

A. Assessment of Agent

The Advisers shall establish that the Agent (i) is independent from the Advisers, (ii) has resources that indicate it can competently provide analysis of proxy issues, and (iii) can make recommendations in an impartial manner and in the best interests of the clients and, where applicable, their beneficial owners. The Advisers shall utilize, and the Agent shall comply with, such methods for establishing the foregoing as the Advisers may deem reasonably appropriate and shall do so not less than annually as well as prior to engaging the services of any new proxy voting service. The Agent shall also notify the Advisers in writing within fifteen (15) calendar days of any material change to information previously provided to an Adviser in connection with establishing the Agent's independence, competence or impartiality.

B. Conflicts of Interest

As fiduciaries to their clients, each Adviser puts the interests of its clients ahead of its own. In order to ensure that relevant personnel of the Advisers are able to identify potential material conflicts of interest, each Adviser will take the following steps:

Eaton Vance National Municipal Opportunities Trust 58 SAI dated July 22, 2021
· Quarterly, the Eaton Vance Legal and Compliance Department will seek information from the department heads of each department of the Advisers and of Eaton Vance Distributors, Inc. ('EVD') (an affiliate of the Advisers and principal underwriter of certain Eaton Vance Funds). Each department head will be asked to provide a list of significant clients or prospective clients of the Advisers or EVD.
· A representative of the Legal and Compliance Department will compile a list of the companies identified (the 'Conflicted Companies') and provide that list to the Proxy Administrator.
· The Proxy Administrator will compare the list of Conflicted Companies with the names of companies for which he or she has been referred a proxy statement (the 'Proxy Companies'). If a Conflicted Company is also a Proxy Company, the Proxy Administrator will report that fact to the Global Proxy Group.
· If the Proxy Administrator expects to instruct the Agent to vote the proxy of the Conflicted Company strictly according to the Guidelines contained in these Proxy Voting Policies and Procedures (the 'Policies') or the recommendation of the Agent, as applicable, he or she will (i) inform the Global Proxy Group of that fact, (ii) instruct the Agent to vote the proxies and (iii) record the existence of the material conflict and the resolution of the matter.
· If the Proxy Administrator intends to instruct the Agent to vote in a manner inconsistent with the Guidelines, the Global Proxy Group will then determine if a material conflict of interest exists between the relevant Adviser and its clients (in consultation with the Legal and Compliance Department if needed). If the Global Proxy Group determines that a material conflict exists, prior to instructing the Agent to vote any proxies relating to these Conflicted Companies the Adviser will seek instruction on how the proxy should be voted from:
· The client, in the case of an individual, corporate, institutional or benefit plan client;
· In the case of a Fund, its board of directors, any committee, sub-committee or group of Independent Trustees (as long as such committee, sub-committee or group contains at least two or more Independent Trustees); or
· The adviser, in situations where the Adviser acts as a sub-adviser to such adviser.

The Adviser will provide all reasonable assistance to each party to enable such party to make an informed decision.

If the client, Fund board or adviser, as the case may be, fails to instruct the Adviser on how to vote the proxy, the Adviser will generally instruct the Agent, through the Proxy Administrator, to abstain from voting in order to avoid the appearance of impropriety. If however, the failure of the Adviser to vote its clients' proxies would have a material adverse economic impact on the Advisers' clients' securities holdings in the Conflicted Company, the Adviser may instruct the Agent, through the Proxy Administrator, to vote such proxies in order to protect its clients' interests. In either case, the Proxy Administrator will record the existence of the material conflict and the resolution of the matter.

The Advisers shall also identify and address conflicts that may arise from time to time concerning the Agent. Upon the Advisers' request, which shall be not less than annually, and within fifteen (15) calendar days of any material change to such information previously provided to an Adviser, the Agent shall provide the Advisers with such information as the Advisers deem reasonable and appropriate for use in determining material relationships of the Agent that may pose a conflict of interest with respect to the Agent's proxy analysis or recommendations. Such information shall include, but is not limited to, a monthly report from the Agent detailing the Agent's Corporate Securities Division clients and related revenue data. The Advisers shall review such information on a monthly basis. The Proxy Administrator shall instruct the Agent to refer any proxies for which a material conflict of the Agent is deemed to be present to the Proxy Administrator. Any such proxy referred by the Agent shall be referred to the Global Proxy Group for consideration accompanied by the Agent's written analysis and voting recommendation. The Proxy Administrator will instruct the Agent to vote the proxy as recommended by the Global Proxy Group.

(1) The Guidelines will prescribe how a proposal shall be voted or provide factors to be considered on a case-by-case basis by the Agent in recommending a vote pursuant to the Guidelines.
Eaton Vance National Municipal Opportunities Trust 59 SAI dated July 22, 2021

Eaton Vance National Municipal Opportunities Trust

Statement of Additional Information

July 22, 2021

_______________

Investment Adviser and Administrator

Eaton Vance Management

Two International Place

Boston, MA 02110

Custodian

State Street Bank and Trust Company

State Street Financial Center, One Lincoln Street

Boston, MA 02111

Transfer Agent

American Stock Transfer & Trust Company, LLC

6201 15th Avenue

Brooklyn, NY 11219

Independent Registered Public Accounting Firm

Deloitte & Touche LLP

200 Berkeley Street

Boston, MA 02116

Eaton Vance National Municipal Opportunities Trust 60 SAI dated July 22, 2021

PART C

OTHER INFORMATION

ITEM 25. FINANCIAL STATEMENTS AND EXHIBITS

(1) FINANCIAL STATEMENTS:

Included in Part A:

Financial Highlights.

Included in Part B:

Registrant's Certified Shareholder Report on Form N-CSR filed May 26, 2021 (Accession No. 0001193125-21-173500) and incorporated herein by reference.

_______________________________

(2) EXHIBITS:

(a) (1) Agreement and Declaration of Trust dated January 26, 2009 filed as Exhibit (a) is incorporated herein by reference to the Registrant's initial Registration Statement on Form N-2 (File Nos. 333-156948 and 811-22269) as to the Registrant's common shares of beneficial interest ('Common Shares') filed with the Securities and Exchange Commission on January 26, 2009 (Accession No. 0000940394-09-000042) ('Initial Common Shares Registration Statement').
(2) Amendment to Declaration of Trust effective April 3, 2009 filed as Exhibit (a)(2) is incorporated herein by reference to Pre-Effective Amendment No. 1 to the Registrant's Initial Common Shares Registration Statement as filed with the Securities and Exchange Commission on April 21, 2009 (Accession No. 0001193125-09-083055) ('Pre-Effective Amendment No. 1').
(b) Amended and Restated By-Laws dated August 13, 2020 is incorporated herein by reference to the Registrant's Form 8-K filed with the Securities and Exchange Commission on August 13, 2020 (Accession No. 0000940394-20-001218).
(c) Not applicable.
(d) Form of Specimen Certificate for Common Shares of Beneficial Interest filed as Exhibit (d) is incorporated herein by reference to the Registrant's Pre-Effective Amendment No. 1.
(e) Form of Dividend Reinvestment Plan filed as Exhibit (e) is incorporated herein by reference to the Registrant's Pre-Effective Amendment No. 1.
(f) Not applicable.
(g) Investment Advisory and Administrative Agreement dated March 1, 2021 filed herewith.
(h) (1) Form of Underwriting Agreement filed as Exhibit (h)(1) is incorporated herein by reference to Pre-Effective Amendment No. 2 to the Registrant's Initial Common Shares Registration Statement as filed with the Securities and Exchange Commission on May 21, 2009 (Accession No. 0001193125-09-116876) ('Pre-Effective Amendment No. 2').
(2) Form of Master Agreement Among Underwriters filed as Exhibit (h)(2) is incorporated herein by reference to Pre-Effective Amendment No. 1.
(3) Form of Master Selected Dealers Agreement filed as Exhibit (h)(3) is incorporated herein by reference to Pre-Effective Amendment No. 1.
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(4) Form of Distribution Agreement with respect to the Rule 415 shelf offering is incorporated by reference to Pre-Effective Amendment No. 1 to the Registrant's Shelf Registration Statement filed with the Securities and Exchange Commission on November 19, 2019 (Accession No. 0000940394-19-001512) ('Form of Distribution Agreement').
(5) Form of Sub-Placement Agent Agreement between Eaton Vance Distributors, Inc. and UBS Securities LLC is incorporated by reference to Pre-Effective Amendment No. 1 to the Registrant's Shelf Registration Statement filed with the Securities and Exchange Commission on November 19, 2019 (Accession No. 0000940394-19-001512) ('Form of Sub-Placement Agent Agreement').
(i) The Securities and Exchange Commission has granted the Registrant an exemptive order that permits the Registrant to enter into deferred compensation arrangements with its independent Trustees. See in the matter of Capital Exchange Fund, Inc., Release No. IC- 20671 (November 1, 1994).
(j) (1) Amended and Restated Master Custodian Agreement between Eaton Vance Funds and State Street Bank & Trust Company dated September 1, 2013 filed as Exhibit (g)(1) is incorporated herein by reference to Post-Effective Amendment No. 211 of Eaton Vance Mutual Funds Trust (File Nos. 002-90946, 811-04015) filed September 24, 2013 (Accession No. 0000940394-13-001073).
(2) Amended and Restated Services Agreement with State Street Bank & Trust Company dated as of September 1, 2010 filed as Exhibit (j)(2) is incorporated herein by reference to Pre-Effective Amendment No. 3 to the Eaton Vance Municipal Income 2028 Term Trust Registration Statement on Form N-2 (File Nos. 333-185340, 811-22777) filed with the Securities and Exchange Commission on March 22, 2013 (Accession No. 0001193125-13-122398).
(3) Amendment Number 1 dated May 16, 2012 to Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as Exhibit (g)(3) is incorporated herein by reference to Post-Effective Amendment No. 39 of Eaton Vance Municipals Trust II (File Nos. 033-71320, 811-08134) filed May 29, 2012 (Accession No. 0000940394-12-000641).
(4) Amendment dated September 1, 2013 to Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as Exhibit (g)(4) is incorporated herein by reference to Post-Effective Amendment No. 211 of Eaton Vance Mutual Funds Trust (File Nos. 002-90946, 811-04015) filed September 24, 2013 (Accession No. 0000940394-13-001073).
(5) Amendment dated July 18, 2018 and effective June 29, 2018 to Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as Exhibit (g)(5) to Post-Effective Amendment No. 212 filed July 31, 2018 (Accession No. 0000940394-18-001408) and incorporated herein by reference.
(6) Amendment dated August 13, 2020 and effective May 29, 2020 to Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as Exhibit (h)(1)(e) is incorporated herein by reference to Post-Effective Amendment No. 79 of Eaton Vance Investment Trust (File Nos. 033-01121, 811-04443) filed September 24, 2020 (Accession No. 0000940394-20-001312).
(k) (1) Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 3 to the initial Registration Statement on Form N-2 of Eaton Vance Tax-Managed Global Diversified Equity Income Fund (File Nos. 333-138318, 811-21973) filed February 21, 2007 (Accession No. 0000950135- 07- 000974).
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(2) Amendment dated April 21, 2008 to Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 1 to the initial Registration Statement on Form N-2 of Eaton Vance National Municipal Opportunities Trust (File Nos. 333-156948, 811-22269) filed April 21, 2009 (Accession No. 0000950135- 09- 083055).
(3) Amendment dated June 13, 2012 to Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 2 to the initial Registration Statement on Form N-2 of Eaton Vance High Income 2021 Target Term Trust (File Nos. 333-209436, 811-23136) filed April 25, 2016 (Accession No. 0000950135- 16- 552383).
(4) Organizational and Expense Reimbursement Agreement dated April 16, 2009 filed as Exhibit (k)(2) is incorporated herein by reference to Pre-Effective Amendment No. 1.
(5) Form of Shareholder Servicing Fee Agreement with UBS Securities LLC filed as Exhibit (k)(3) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(6) Form of Marketing and Structuring Fee Agreement with Morgan Stanley & Co. Incorporated filed as Exhibit (k)(4) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(7) Form of Structuring Fee Agreement with Citigroup Global Markets Inc. filed as Exhibit (k)(5) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(8) Form of Additional Compensation Agreement with Merrill Lynch, Pierce, Fenner & Smith Incorporated filed as Exhibit (k)(6) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(9) Form of Structuring Fee Agreement with Wachovia Capital Markets, LLC filed as Exhibit (k)(7) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(10) Form of Additional Compensation Agreement with qualifying underwriters filed as Exhibit (k)(8) is incorporated herein by reference to Pre-Effective Amendment No. 2.
(l) Opinion of Internal Counsel filed herewith.
(m) Not applicable.
(n) Consent of Independent Registered Public Accounting Firm filed herewith.
(o) Not applicable.
(p) Letter Agreement with Eaton Vance Management dated April 14, 2009 filed as Exhibit (p) is incorporated herein by reference to Pre-Effective Amendment No. 1.
(q) Not applicable.
(r) (1) Code of Ethics adopted by the Eaton Vance Funds effective April 8, 2020 filed as Exhibit (p)(1)(a) to Post-Effective Amendment No. 198 of Eaton Vance Special Investment Trust (File Nos. 002-27962, 811-01545) filed April 27, 2020 (Accession No. 0000940394-20-000815) and incorporated herein by reference.
(2) Code of Ethics adopted by the Eaton Vance Entities effective June 1, 2021 filed as Exhibit (p)(1)(b) to Post-Effective Amendment No. 238 of Eaton Vance Growth Trust (File Nos. 002-22019, 811-01241) filed June 24, 2021 (Accession No. 0000940394-21-000047) and incorporated herein by reference.
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(s) (1) Secretary's Certificate dated January 20, 2021 filed as Exhibit (s)(2) to Post-Effective Amendment No. 3 of Eaton Vance Enhanced Equity Income Fund (File No. 333-229447, 811-21614) filed January 21, 2021 (Accession No. 0000940394-20-000071) and incorporated herein by reference.
(2) Power of Attorney dated June 18, 2021 filed herewith.
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ITEM 26. MARKETING ARRANGEMENTS

See Form of Distribution Agreement with respect to the Rule 415 shelf offering.

See Form of Sub-Placement Agent Agreement between Eaton Vance Distributors, Inc. and UBS Securities LLC.

ITEM 27. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

The approximate expenses in connection with the offering are as follows:

Registration and Filing Fees $ 6,572
FINRA Fees $ 7,591
New York Stock Exchange Fees $ 16,915
Costs of Printing and Engraving $ 0
Accounting Fees and Expenses $ 2,050
Legal Fees and Expenses $ 4,000
Total $ 37,128
* The Adviser will pay expenses of the offering (other than the applicable commissions).
ITEM 28. PERSONS CONTROLLED BY OR UNDER COMMON CONTROL

None.

ITEM 29. NUMBER OF HOLDERS OF SECURITIES

Set forth below is the number of record holders as of June 30, 2021, of each class of securities of the Registrant:

Title of Class Number of Record Holders
Common Shares of Beneficial interest, par value $0.01 per share 10,195
ITEM 30. INDEMNIFICATION

The Registrant's Amended and Restated By-Laws and the Form of Distribution Agreement contain provisions limiting the liability, and providing for indemnification, of the Trustees and officers under certain circumstances.

The Registrant's Trustees and officers are insured under a standard investment company errors and omissions insurance policy covering loss incurred by reason of negligent errors and omissions committed in their official capacities as such. Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended (the 'Securities Act'), may be permitted to directors, officers and controlling persons of the Registrant pursuant to the provisions described in this Item 30, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

ITEM 31. BUSINESS AND OTHER CONNECTIONS OF INVESTMENT ADVISER

Reference is made to: (i) the information set forth under the caption 'Investment advisory and other services' in the Statement of Additional Information; (ii) the Morgan Stanley 10-K filed under the Securities and Exchange Act of 1934 (file No. 001-11758); the Eaton Vance Corp. 10-K filed under the Securities Exchange Act of 1934 (File No. 001-8100); and (iii) the Form ADV of Eaton Vance Management (File No. 801-15930) filed with the Commission, all of which are incorporated herein by reference.

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ITEM 32. LOCATION OF ACCOUNTS AND RECORDS

All applicable accounts, books and documents required to be maintained by the Registrant by Section 31(a) of the Investment Company Act of 1940 and the Rules promulgated thereunder are in the possession and custody of the Registrant's custodian, State Street Bank and Trust Company, State Street Financial Center, One Lincoln Street, Boston, MA 02111, and its transfer agent, American Stock Transfer & Trust Company, LLC, 6201 15th Avenue, Brooklyn, NY 11219, with the exception of certain corporate documents and portfolio trading documents which are in the possession and custody of Eaton Vance Management, Two International Place, Boston, MA 02110. Registrant is informed that all applicable accounts, books and documents required to be maintained by registered investment advisers are in the custody and possession of Eaton Vance Management.

ITEM 33. MANAGEMENT SERVICES

Not applicable.

ITEM 34. UNDERTAKINGS

1. The Registrant undertakes to suspend the offering of Common Shares until the prospectus is amended if (1) subsequent to the effective date of this Registration Statement, the net asset value declines more than 10 percent from its net asset value as of the effective date of this Registration Statement or (2) the net asset value increases to an amount greater than its net proceeds as stated in the prospectus.

2. Not applicable.

3. The Registrant undertakes to

(a) file, during any period in which offers or sales are being made, a post-effective amendment to the registration statement:

(1) to include any prospectus required by Section 10(a)(3) of the Securities Act;

(2) to reflect in the prospectus any facts or events after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price set forth in the 'Calculation of Registration Fee' table in the effective registration statement;

(3) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement.

(b) that, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of those securities at that time shall be deemed to be the initial bona fide offering thereof;

(c) to remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering;

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(d) that, for the purpose of determining liability under the Securities Act to any purchaser:

(1) if the Registrant is relying on Rule 430B [17 CFR 230.430B]:

(A) Each prospectus filed by the Registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(B) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (x), or (xi) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date; or

(2) if the Registrant is subject to Rule 430C [17 CFR 230.430C]: each prospectus filed pursuant to Rule 424(b) under the Securities Act as part of a registration statement relating to an offering, other than registration statements relying on Rule 430B or other than prospectuses filed in reliance on Rule 430A, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such date of first use.

(e) that for the purpose of determining liability of the Registrant under the Securities Act to any purchaser in the initial distribution of securities: The undersigned Registrant undertakes that in a primary offering of securities of the undersigned Registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned Registrant will be a seller to the purchaser and will be considered to offer or sell such securities to the purchaser:

(1) any preliminary prospectus or prospectus of the undersigned Registrant relating to the offering required to be filed pursuant to Rule 424 under the Securities Act;

(2) free writing prospectus relating to the offering prepared by or on behalf of the undersigned Registrant or used or referred to by the undersigned Registrants;

(3) the portion of any other free writing prospectus or advertisement pursuant to Rule 482 under the Securities Act relating to the offering containing material information about the undersigned Registrant or its securities provided by or on behalf of the undersigned Registrant; and

(4) any other communication that is an offer in the offering made by the undersigned Registrant to the purchaser.

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4. The Registrant undertakes that:

(a) for the purpose of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this Registration Statement in reliance upon Rule 430A and contained in the form of prospectus filed by the Registrant under the Securities Act shall be deemed to be part of the Registration Statement as of the time it was declared effective; and

(b) for the purpose of determining any liability under the Securities Act, each post- effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

5. Not applicable.

6. Not applicable.

7. The Registrant undertakes to send by first class mail or other means designed to ensure equally prompt delivery, within two business days of receipt of an oral or written request, its Statement of Additional Information.

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NOTICE

A copy of the Agreement and Declaration of Trust of Eaton Vance National Municipal Opportunities Trust is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and that the obligations of or arising out of this instrument are not binding upon any of the Trustees, officers or shareholders individually, but are binding only upon the assets and property of the Registrant.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended and the Investment Company Act of 1940, as amended the Registrant has duly caused this Amendment to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of Boston and the Commonwealth of Massachusetts, on the 22nd day of July, 2021.

EATON VANCE NATIONAL MUNICIPAL
OPPORTUNITIES TRUST
By: Eric A. Stein*
Eric A. Stein, President

Pursuant to the requirements of the Securities Act of 1933, as amended this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

Signature Title
Eric A. Stein* President (Chief Executive Officer)
Eric A. Stein
James F. Kirchner* Treasurer (Principal Financial and Accounting Officer)
James F. Kirchner
Signature Title Signature Title
Thomas E. Faust Jr.* Trustee Helen Frame Peters* Trustee
Thomas E. Faust Jr. Helen Frame Peters
Mark R. Fetting* Trustee Keith Quinton* Trustee
Mark R. Fetting Keith Quinton
Cynthia E. Frost* Trustee Marcus L. Smith* Trustee
Cynthia E. Frost Marcus L. Smith
George J. Gorman* Trustee Susan J. Sutherland* Trustee
George J. Gorman Susan J. Sutherland
Valerie A. Mosley* Trustee Scott E. Wennerholm* Trustee
Valerie A. Mosley Scott E. Wennerholm
William H. Park* Trustee
William H. Park
*By: /s/Deidre E. Walsh
Deidre E. Walsh (As attorney-in-fact)
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INDEX TO EXHIBITS

Exhibit No.
Description
(g) Investment Advisory and Administrative Agreement
(l) Opinion of Internal Counsel
(n) Consent of Independent Registered Public Accounting Firm
(s) (2) Power of Attorney
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