Summary Prospectus by Investment Company - Form 497K

The Fund seeks current income exempt from federal and California income taxes.

The table below describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and example below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the MainStay Funds. This amount may vary depending on the MainStay Fund in which you invest. In addition, different financial intermediary firms and financial professionals may impose different sales loads and waivers. More information about these and other discounts or waivers is available from your financial professional, in the "Information on Sales Charges" section starting on page 133 of the Prospectus and Appendix A - Intermediary-Specific Sales Charge Waivers and Discounts, and in the "Alternative Sales Arrangements" section on page 142 of the Statement of Additional Information.

1. No initial sales charge applies on investments of $250,000 or more (and certain other qualified purchases). However, a contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within 18 months of the date of purchase on shares that were purchased without an initial sales charge.

2.Restated to reflect current management fees. The management fee is as follows: 0.45% on assets up to $1 billion; 0.43% on assets from $1 billion to $3 billion; and 0.42% on assets over $3 billion.

The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated whether or not you redeem all of your shares at the end of those periods (except as indicated with respect to Class C shares). The Example reflects Class C and Class C2 shares converting into Investor Class shares in years 9-10; expenses could be lower if you are eligible to convert to Class A shares instead. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects the contractual fee waiver and/or expense reimbursement arrangement, if applicable, for the current duration of the arrangement only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 17% of the average value of its portfolio.

(NYLIM) NL048 MSCTF01a-08/22

The Fund, under normal circumstances, invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in municipal bonds, whose interest is, in the opinion of bond counsel for the issuers at the time of issuance, exempt from federal and California income taxes.

Municipal bonds are generally debt obligations issued by or on behalf of states, territories and possessions of the United States, and their political subdivisions, agencies and instrumentalities that provide income free from federal, state and potentially local income taxes. If the interest on a particular municipal bond is exempt from federal and California income taxes, the Fund will treat the bond as qualifying for purposes of the 80% policy even though the issuer of the bond may be located outside of California. Municipal bonds include, among other instruments, general obligation bonds, revenue bonds, industrial revenue bonds, industrial development bonds, private activity bonds, as well as short-term, tax-exempt obligations such as municipal notes and variable rate demand obligations. The Fund may invest up to 20% of its net assets in municipal bonds subject to the federal alternative minimum tax, and municipal bonds that pay interest that is subject to federal and California income taxes.

Although the Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds, MacKay Shields LLC, the Fund's Subadvisor, intends to invest primarily in investment grade quality bonds as rated by at least one nationally recognized statistical rating organization ("NRSRO") or if unrated, judged to be of comparable quality by the Subadvisor. The Fund may invest up to 20% of its net assets in municipal bonds that are rated below investment grade (commonly referred to as "high-yield securities" or "junk bonds") as rated by at least one NRSRO, including up to 10% of its net assets in municipal bonds that are the subject of bankruptcy proceedings, that are in default as to the payment of principal or interest, or that are rated in the lowest rating category by a NRSRO, or if unrated, judged to be of comparable quality by the Subadvisor ("distressed securities"). If NRSROs assign different ratings to the same security, the Fund will use the higher rating for purposes of determining the security's credit quality.

The Fund may invest more than 25% of its total assets in municipal bonds that are related in such a way that an economic, business or political development or change affecting one such security could also affect the other securities. The Fund generally invests in municipal bonds that have a maturity of five years or longer at the time of purchase.

If the supply of California state tax exempt municipal bonds is insufficient to meet the Fund's investment needs, the Fund may invest in municipal bonds issued by other states. Municipal bonds issued by other states purchased by the Fund will generally be exempt from federal income taxes, but may not be exempt from California income taxes.

The Fund may invest in derivatives, such as futures, options and swap agreements to seek enhanced returns or to reduce the risk of loss by hedging certain of its holdings.

Investment Process: In choosing investments, the Subadvisor analyzes the credit quality of issuers and considers the yields available on municipal bonds with different maturities.

The Subadvisor uses active management in an effort to identify municipal bonds it believes to be mispriced and to build a consistent yield advantage. The Subadvisor focuses on reducing volatility through a disciplined investment process, which includes fundamental, "bottom-up" credit research and risk management. In addition, the Subadvisor reviews macroeconomic events, technicals in the municipal market, tax policies and analyzes individual municipal securities and sectors. The Subadvisor's investment process includes a risk analysis that gives consideration to a variety of security-specific risks, including but not limited to, environmental, social and governance ("ESG") risks that may have a material impact on the performance of a security. In addition to proprietary research, the Subadvisor may use screening tools and, to the extent available, third party data to identify ESG risk factors that may not have been captured through its own research. The Subadvisor's consideration of ESG risk is weighed against other criteria and therefore does not mean that any sectors, industries or individual securities are explicitly excluded from the Fund.

The Subadvisor may sell a security if it no longer believes the security will contribute to meeting the investment objective of the Fund. In considering whether to sell a security, the Subadvisor may evaluate, among other things, the condition of the economy and meaningful changes in the issuer's financial condition.

You can lose money by investing in the Fund. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. The investments selected by the Subadvisor may underperform the market in which the Fund invests or other investments. The Fund may receive large purchase or redemption orders which may have adverse effects on performance if the Fund were required to sell securities, invest cash or hold a relatively large amount of cash at times when it would not otherwise do so.

The principal risks of investing in the Fund are summarized below.

Market Risk: The value of the Fund's investments may fluctuate because of changes in the markets in which the Fund invests, which could cause the Fund to underperform other funds with similar investment objectives and strategies. Such changes may be rapid and unpredictable. From time to time, markets may experience periods of stress for potentially prolonged periods that may result in: (i) increased market volatility; (ii) reduced market liquidity; and (iii) increased redemptions of Fund shares. Such conditions may add significantly to the risk of volatility in the net asset value of the Fund's shares.

Portfolio Management Risk: The investment strategies, practices and risk analyses used by the Subadvisor may not produce the desired results. The Subadvisor may give consideration to certain ESG criteria when evaluating an investment opportunity. The application of ESG criteria may result in the Fund (i) having exposure to certain securities or industry sectors that are significantly different than the composition of the Fund's benchmark; and (ii) performing differently than other funds and strategies in its peer group that do not take into account ESG criteria or the Fund's benchmark.

Yield Risk: There can be no guarantee that the Fund will achieve or maintain any particular level of yield.

Municipal Bond Risk: Municipal bond risks include the inability of the issuer to repay the obligation, the relative lack of information about certain issuers, and the possibility of future tax and legislative changes, which could affect the market for and value of municipal securities. Additional risks include:

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·General Obligation Bonds Risk-timely payments depend on the issuer's credit quality, ability to raise tax revenues and ability to maintain an adequate tax base;

·Revenue Bonds (including Industrial Development Bonds) Risk-timely payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source, and may be negatively impacted by the general credit of the user of the facility;

·Private Activity Bonds Risk-municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise, which is solely responsible for paying the principal and interest on the bond, and payment under these bonds depends on the private enterprise's ability to do so;

·Moral Obligation Bonds Risk-moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality;

·Municipal Notes Risk-municipal notes are shorter-term municipal debt obligations that pay interest that is, in the opinion of bond counsel, generally excludable from gross income for federal income tax purposes (except that the interest may be includable in taxable income for purposes of the federal alternative minimum tax) and that have a maturity that is generally one year or less. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money; and

·Municipal Lease Obligations Risk-in a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property. Municipal leases may pose additional risks because many leases and contracts contain "non-appropriation" clauses that provide that the governmental issuer has no obligation to make future payments under the lease or contract unless money is appropriated for this purpose by the appropriate legislative body.

Municipalities continue to experience political, economic and financial difficulties in the current economic environment. The ability of a municipal issuer to make payments and the value of municipal bonds can be affected by uncertainties in the municipal securities market. Such uncertainties could cause increased volatility in the municipal securities market and could negatively impact the Fund's net asset value and/or the distributions paid by the Fund.

Certain of the issuers in which the Fund may invest have recently experienced, or may experience, significant financial difficulties and repeated credit rating downgrades. For example, in recent years, Puerto Rico has experienced difficult financial, economic and other conditions, which may negatively affect the value of the Fund's holdings in Puerto Rico municipal securities.

To be tax exempt, municipal bonds must meet certain regulatory requirements. If a municipal bond fails to meet such requirements, the interest received by the Fund from its investment in such bonds and distributed to shareholders may be taxable. It is possible that interest on a municipal bond may be declared taxable after the issuance of the bond, and this determination may apply retroactively to the date of the issuance of the bond, which would cause a portion of prior distributions made by the Fund to be taxable to shareholders in the year of receipt.

Municipal Bond Focus Risk: From time to time the Fund may invest a substantial amount of its assets in municipal bonds on which interest is paid solely from revenues of similar projects. If the Fund focuses its investments in this manner, it assumes the legal and economic risks relating to such projects, which may have a significant impact on the Fund's investment performance. In addition, the Fund may invest more heavily in bonds from certain cities or regions than others, which may increase the Fund's exposure to losses resulting from economic, political or regulatory occurrences impacting these particular cities or regions.

Debt Securities Risk: The risks of investing in debt or fixed-income securities include (without limitation): (i) credit risk, e.g., the issuer or guarantor of a debt security may be unable or unwilling (or be perceived as unable or unwilling) to make timely principal and/or interest payments or otherwise honor its obligations, or changes in an issuer's credit rating or the market's perception of an issuer's creditworthiness may affect the value of the Fund's investments; (ii) maturity risk, e.g., a debt security with a longer maturity may fluctuate in value more than one with a shorter maturity; (iii) market risk, e.g., low demand for debt securities may negatively impact their price; (iv) interest rate risk, e.g., when interest rates go up, the value of a debt security generally goes down, and when interest rates go down, the value of a debt security generally goes up (long-term debt securities are generally more susceptible to interest rate risk than short-term debt securities); and (v) call or prepayment risk, e.g., during a period of falling interest rates, the issuer may redeem a security by repaying it early, which may reduce the Fund's income if the proceeds are reinvested at lower interest rates.

Interest rate risk is the risk that the value of the Fund's investments in fixed income or debt securities will change because of changes in interest rates. There is a risk that interest rates across the financial system may change, possibly significantly and/or rapidly. Changes in interest rates or a lack of market participants may lead to decreased liquidity and increased volatility in the fixed-income or debt markets, making it more difficult for the Fund to sell its fixed-income or debt holdings. Decreased liquidity in the fixed-income or debt markets also may make it more difficult to value some or all of the Fund's fixed-income or debt holdings. For most fixed-income investments, when market interest rates fall, prices of fixed-rate debt securities rise. However, when market interest rates fall, prices of certain variable and fixed-rate debt securities may be adversely affected (i.e., falling interest rates bring the possibility of prepayment risk, as an instrument may be redeemed before maturity). Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, may result in heightened market volatility and may detract from Fund performance to the extent the Fund is exposed to such interest rates and/or volatility. Other factors that may affect the value of debt securities include, but are not limited to, economic, political, public health, and other crises and responses by governments and companies to such crises.

Not all U.S. government debt securities are guaranteed by the U.S. government-some are backed only by the issuing agency, which must rely on its own resources to repay the debt. The Fund's yield will fluctuate with changes in short-term interest rates.

Distressed Securities Risk: Investments in distressed securities are subject to substantial risks in addition to the risks of investing in other types of high-yield securities. Distressed securities are speculative and involve substantial risk that principal will not be repaid. Generally, the Fund will not receive interest payments on such securities and may incur costs to protect its investment. In addition, the Fund's ability to sell distressed securities and any securities received in exchange for such securities may be restricted.

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High-Yield Municipal Bond Risk: High-yield or non-investment grade municipal bonds (commonly referred to as "junk bonds") may be subject to increased liquidity risk as compared to other high-yield debt securities. There may be little or no active trading market for certain high-yield municipal bonds, which may make it difficult for the Fund to sell such bonds at or near their perceived value. In such cases, the value of a high-yield municipal bond may decline dramatically, even during periods of declining interest rates. The high-yield municipal bonds in which the Fund intends to invest may be more likely to pay interest that is includable in taxable income for purposes of the federal alternative minimum tax than other municipal bonds.

Derivatives Risk: Derivatives are investments whose value depends on (or is derived from) the value of an underlying instrument, such as a security, asset, reference rate or index. Derivative strategies may expose the Fund to greater risk than if it had invested directly in the underlying instrument and often involve leverage, which may exaggerate a loss, potentially causing the Fund to lose more money than it originally invested and would have lost had it invested directly in the underlying instrument. For example, if the Fund is the seller of credit protection in a credit default swap, the Fund effectively adds leverage to its portfolio and is subject to the credit exposure on the full notional value of the swap. Derivatives may be difficult to sell, unwind and/or value. Derivatives may also be subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Fund. Futures may be more volatile than direct investments in the instrument underlying the contract, and may not correlate perfectly to the underlying instrument. Futures and other derivatives also may involve a small initial investment relative to the risk assumed, which could result in losses greater than if they had not been used. Due to fluctuations in the price of the underlying instrument, the Fund may not be able to profitably exercise an option and may lose its entire investment in an option. To the extent that the Fund writes or sells an option, if the decline in the value of the underlying instrument is significantly below the exercise price in the case of a written put option or increase above the exercise price in the case of a written call option, the Fund could experience a substantial loss. Swaps may be subject to counterparty credit, correlation, valuation, liquidity and leveraging risks. Swap transactions tend to shift a Fund's investment exposure from one type of investment to another and may entail the risk that a party will default on its payment obligations to the Fund. Additionally, applicable regulators have adopted rules imposing certain margin requirements, including minimums on uncleared swaps, which may result in the Fund and its counterparties posting higher margin amounts for uncleared swaps. Certain standardized swaps are subject to mandatory central clearing and exchange trading. Central clearing, which interposes a central clearinghouse to each participant's swap, and exchange trading are intended to reduce counterparty credit risk and increase liquidity but neither makes swap transactions risk-free. Derivatives may also increase the expenses of the Fund.

Private Placement and Restricted Securities Risk: The Fund may invest in privately issued securities, including those which may be resold only in accordance with Rule 144A under the Securities Act of 1933, as amended. Securities acquired in a private placement generally are subject to strict restrictions on resale, and there may be no market or a limited market for the resale of such securities. Therefore, the Fund may be unable to dispose of such securities when it desires to do so or at the most favorable price. This potential lack of liquidity also may make it more difficult to accurately value these securities.

Liquidity and Valuation Risk: The Fund's investments may be illiquid at the time of purchase or liquid at the time of purchase and subsequently become illiquid due to, among other things, events relating to the issuer of the securities, market events, operational issues, economic conditions, investor perceptions or lack of market participants. The lack of an active trading market may make it difficult to sell or obtain an accurate price for a security. If market conditions or issuer specific developments make it difficult to value securities, the Fund may value these securities using more subjective methods, such as fair value pricing. In such cases, the value determined for a security could be different than the value realized upon such security's sale. As a result, an investor could pay more than the market value when buying shares or receive less than the market value when selling shares. This could affect the proceeds of any redemption or the number of shares an investor receives upon purchase. The Fund is subject to the risk that it could not meet redemption requests within the allowable time period without significant dilution of remaining investors' interests in the Fund. To meet redemption requests or to raise cash to pursue other investment opportunities, the Fund may be forced to sell securities at an unfavorable time and/or under unfavorable conditions, which may adversely affect the Fund's performance. These risks are heightened for fixed-income instruments because of the current low interest rate environment.

California State Specific Risk: Because the Fund invests in municipal bonds issued by or on behalf of the State of California, and its political subdivisions, agencies and instrumentalities, events in California may affect the Fund's investments and performance. These events may include fiscal or political policy changes, tax base erosion, budget deficits and other financial difficulties. Any deterioration of California's fiscal situation and economic situation of its municipalities could cause greater volatility and increase the risk of investing in California.

Tax Risk: Income from municipal bonds held by the Fund could be declared taxable because of unfavorable changes in tax law, adverse interpretations by the Internal Revenue Service, state tax authorities or noncompliant conduct of a bond issuer.

Money Market/Short-Term Securities Risk: To the extent the Fund holds cash or invests in money market or short-term securities, the Fund may be less likely to achieve its investment objective. In addition, it is possible that the Fund's investments in these instruments could lose money.

Variable Rate Demand Instruments Risk: A variable rate demand instrument is generally subject to certain of the risks associated with debt securities. Variable rate demand instruments are also subject to potential delays between the instrument's periodic interest rate reset and an intervening rise in general interest rates, which could adversely affect the Fund. In addition, these instruments are subject to the risk that, if not held to maturity, the Fund will be subject to the credit risk of any third party supporting or providing the instrument's demand feature, as well as the risk that such third party's obligations may terminate or that it may otherwise fail to meet such obligations.

The following bar chart and table indicate some of the risks of investing in the Fund. The bar chart shows you how the Fund's calendar year performance has varied over time. Sales loads, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. The average annual total returns table shows how the Fund's average annual total returns (before and after taxes) compare to those of a broad-based securities market index. The Fund has selected the Bloomberg California Municipal Bond Indexas its primary benchmark. The Bloomberg California Municipal Bond Index is a market value-weighted index of California investment grade tax exempt fixed-rate municipal bonds with maturities of one year or more.

Index returns reflect no deductions for fees, expenses or taxes, except for foreign withholding taxes where applicable.

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Performance data for the classes varies based on differences in their fee and expense structures. Performance data is not shown for classes with less than one calendar year of performance. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Please visit newyorklifeinvestments.com/funds for more recent performance information.

Annual Returns, Class I Shares

(by calendar year 2014-2021)

Average Annual Total Returns (for the periods ended December 31, 2021)

After-tax returns are calculated using the highest individual federal marginal income tax rates in effect at the time of each distribution or capital gain or upon the sale of Fund shares, and do not reflect the impact of state and local taxes. In some cases, the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of shares at the end of the measurement period. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns are not relevant if you hold your shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns shown are for Class I shares. After-tax returns for the other share classes may vary.

New York Life Investment Management LLC serves as the Fund's Manager. MacKay Shields LLC serves as the Subadvisor. The individuals listed below are jointly and primarily responsible for the day-to-day portfolio management of the Fund.

You may purchase or sell shares of the Fund on any day the Fund is open for business by contacting your financial adviser or financial intermediary firm, or by contacting the Fund by telephone at 800-624-6782, by mail at MainStay Funds, P.O. Box 219003, Kansas City, MO 64121-9000, by overnight mail to

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430 West 7^th Street, Suite 219003, Kansas City, MO 64105-1407, or by accessing our website at newyorklifeinvestments.com/accounts. Class R6 shares are generally only available to certain retirement plans invested in the Fund through omnibus accounts (either at the plan level or omnibus accounts held on the books of the Fund). Class R6 shares are generally not available to retail accounts. Generally, an initial investment minimum of $2,500 applies if you invest in Investor Class, Class C or Class C2 shares, $15,000 for Class A shares and $1,000,000 for individual investors in Class I shares investing directly (i) with the Fund; or (ii) through certain private banks and trust companies that have an agreement with NYLIFE Distributors LLC, the Fund's principal underwriter and distributor, or its affiliates. A subsequent investment minimum of $50 applies to investments in Investor Class, Class C and Class C2 shares. These initial investment minimum and subsequent purchase amounts also apply to Investor Class and Class C shares purchased through AutoInvest, MainStay's systematic investment plan. Class A shares have no subsequent investment minimum. Class R6 shares and institutional shareholders in Class I shares have no initial or subsequent investment minimums.

Certain financial intermediaries through whom you may invest may impose their own investment minimums, fees, policies and procedures for purchasing and selling Fund shares, which are not described in this Prospectus or the Statement of Additional Information, and which will depend on the policies, procedures and trading platforms of the financial intermediary. Consult a representative of your financial intermediary about the availability of shares of the Fund and the intermediary's policies, procedures and other information.

The Fund's distributions are generally expected to be exempt from federal and California state income tax. However, a portion of the distributions may be subject to the alternative minimum tax. Additionally, the Fund may derive taxable income and/or capital gains. Distributions to shareholders of any such taxable income or capital gains, unless you are investing through a tax-deferred arrangement, such as a 401(k) plan or an individual retirement account, generally will be taxable.

If you purchase Fund shares through a financial intermediary firm (such as a broker/dealer or bank), the Fund and its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary firm or your financial adviser to recommend the Fund over another investment. Ask your financial adviser or visit your financial intermediary firm's website for more information. No compensation, administrative payments, sub-transfer agency payments or service payments are paid to broker/dealers or other financial intermediaries from Fund assets or the Distributor's or an affiliate's resources on sales of or investments in Class R6 shares. The Distributor or an affiliate may pay de minimis amounts to intermediaries for setup, connectivity or other technological expenses. Class R6 shares do not carry sales charges or pay Rule 12b-1 fees, or make payments to financial intermediaries to assist in, or in connection with, the sale of the Fund's shares.

"New York Life Investments" is both a service mark, and the common trade name, of certain investment advisors affiliated with New York Life Insurance Company.

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