# EDGAR Filing Document

**Accession Number:** 0000787441
**File Stem:** 0001741773-23-000573
**Filing Date:** 2023-2
**Character Count:** 54513
**Document Hash:** 41581c77c4f954ba9b4c568dd12f817b
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001741773-23-000573.hdr.sgml**: 20230228

**ACCESSION NUMBER**: 0001741773-23-000573

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20230228

**DATE AS OF CHANGE**: 20230228

**EFFECTIVENESS DATE**: 20230228

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MAINSTAY FUNDS
- **CENTRAL INDEX KEY:** 0000787441
- **IRS NUMBER:** 000000000
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 1031

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 033-02610
- **FILM NUMBER:** 23678745

**BUSINESS ADDRESS:**
- **STREET 1:** 51 MADISON AVE
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10010
- **BUSINESS PHONE:** 2125767000

**MAIL ADDRESS:**
- **STREET 1:** 51 MADISON AVENUE
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10010

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MACKAY SHIELDS MAINSTAY SERIES FUND /NY/
- **DATE OF NAME CHANGE:** 19911126

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MACKAY SHIELDS SERIES FUND
- **DATE OF NAME CHANGE:** 19860506

## Series and Classes Contracts Data

### MainStay MacKay Strategic Bond Fund (Series ID: S000006894)

| Class ID   | Class Name     | Ticker Symbol   |
|:---|:---|:---|
| C000018685 | Class A        | MASAX           |
| C000018686 | Class B        | MASBX           |
| C000018687 | Class C        | MSICX           |
| C000018688 | Class I        | MSDIX           |
| C000060790 | INVESTOR CLASS | MSYDX           |
| C000138226 | Class R2       | MSIRX           |
| C000166834 | Class R3       | MSDJX           |
| C000185554 | Class R6       | MSYEX           |

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| | | |
|:---|:---|:---|
| &nbsp;&nbsp;![](img_694508506b0c4f1.jpg)<br>**MainStay MacKay Strategic Bond Fund** | &nbsp;&nbsp;![](img_694508506b0c4f1.jpg)<br>**MainStay MacKay Strategic Bond Fund** | **Summary Prospectus**<br>February 28, 2023  |
| &nbsp;&nbsp;**Class**/Ticker | **A** MASAX **Investor** MSYDX **B** MASBX **C** MSICX **I** MSDIX **R2** MSIRX **R3** MSDJX **R6** MSYEX | **A** MASAX **Investor** MSYDX **B** MASBX **C** MSICX **I** MSDIX **R2** MSIRX **R3** MSDJX **R6** MSYEX |

---

Before you invest, you may want to review the Fund's Prospectus, which contains more information about the Fund and its risks. You can find the Fund's Prospectus, reports to shareholders and other information about the Fund by going online to newyorklifeinvestments.com, by calling 800-624-6782 or by sending an e-mail to MainStayShareholderServices@nylim.com. The Fund's Prospectus and Statement of Additional Information, both dated February 28, 2023, as may be amended from time to time, are incorporated by reference into this Summary Prospectus.

**Investment Objective**

The Fund seeks total return by investing primarily in domestic and foreign debt securities.

**Fees and Expenses of the Fund** 

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 $100,000 in the Fund. 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 152 of the Prospectus and Appendix A – Intermediary-Specific Sales Charge Waivers and Discounts, and in the "Alternative Sales Arrangements" section on page 138 of the Statement of Additional Information.

---

| | | | | | | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Class A** | **Investor Class** | **Class B<sup>1</sup>** | **Class B<sup>1</sup>** | **Class C** | **Class C** | **Class I** | **Class R2** | **Class R2** | **Class R3**  | **Class R3**  | **Class R6**  | **Class R6**  |
| **Shareholder Fees** (fees paid directly from your investment) |  |  |  |  |  |  |  |  |  |  |  |  |  |
| Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) | 4.50 | 4.00 |  |  |  |  |  |  |  |  |  |  |  |
| Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds) | None<br><sup>2</sup>  | None<br><sup>2</sup>  | 5.00 | % | 1.00 | % |  |  |  |  |  |  |  |
| **Annual Fund Operating Expenses** (expenses that you pay each year as a percentage of the value of your investment) |  |  |  |  |  |  |  |  |  |  |  |  |  |
| Management Fees (as an annual percentage of the Fund's average daily net assets)<sup>3</sup> | 0.59 | 0.59 | 0.59 | % | 0.59 | % | 0.59 | 0.59 | % | 0.59 | % | 0.59 | % |
| Distribution and/or Service (12b-1) Fees | 0.25 | 0.25 | 1.00 | % | 1.00 | % |  | 0.25 | % | 0.50 | % |  |  |
| Other Expenses | 0.19 | 0.33 | 0.33 | % | 0.33 | % | 0.19 | 0.29 | % | 0.29 | % | 0.06 | % |
| Total Annual Fund Operating Expenses | 1.03 | 1.17 | 1.92 | % | 1.92 | % | 0.78 | 1.13 | % | 1.38 | % | 0.65 | % |
| Waivers / Reimbursements<sup>4</sup> | 0.00 | 0.00 | 0.00 | % | 0.00 | % | (0.08 | 0.00 | % | 0.00 | % | 0.00 | % |
| Total Annual Fund Operating Expenses After Waivers / Reimbursements<sup>4</sup> | 1.03 | 1.17 | 1.92 | % | 1.92 | % | 0.70 | 1.13 | % | 1.38 | % | 0.65 | % |

---

1. Class B shares are closed to all new purchases as well as additional investments by existing Class B shareholders.

2. No initial sales charge applies on investments of $1 million 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.

3. Restated to reflect current management fees: The management fee is as follows: 0.60% on assets up to $500 million; 0.55% on assets from $500 million up to $1 billion; 0.50% on assets from $1 billion to $5 billion; and 0.475% on assets over $5 billion.

4. New York Life Investment Management LLC ("New York Life Investments") has contractually agreed to waive fees and/or reimburse expenses so that Total Annual Fund Operating Expenses (excluding taxes, interest expenses (including interest on securities sold short), litigation, extraordinary expenses, brokerage and other transaction expenses relating to the purchase or sale of portfolio investments, and acquired (underlying) fund fees and expenses) for Class I shares do not exceed 0.70% of its average daily net assets. This agreement will remain in effect until February 28, 2024, and shall renew automatically for one-year terms unless New York Life Investments provides written notice of termination prior to the start of the next term or upon approval of the Board of Trustees of the Fund.

**Example**

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 B and Class C shares). The Example reflects Class B and Class C 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:

<br> (NYLIM) NL052 MSSB01 -02/23

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| | | | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **&nbsp;&nbsp;&nbsp;&nbsp;Expenses After** | **Class A** | **Investor** | **Class B** | **Class B** | **Class C** | **Class C** | **Class I** | **Class R2** | **Class R3** | **Class R6** |
|  |  | **Class** | Assuming no redemption | Assuming redemption at end of period | Assuming no redemption | Assuming redemption at end of period |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;1 Year | $&nbsp;&nbsp;&nbsp;&nbsp; 550 | $&nbsp;&nbsp;&nbsp;&nbsp; 514 | $&nbsp;&nbsp;&nbsp;&nbsp; 195 | $&nbsp;&nbsp;&nbsp;&nbsp; 695 | $&nbsp;&nbsp;&nbsp;&nbsp; 195 | $&nbsp;&nbsp;&nbsp;&nbsp; 295 | $&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;72 | $&nbsp;&nbsp;&nbsp;&nbsp; 115 | $&nbsp;&nbsp;&nbsp;&nbsp; 140 | $&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;66 |
| &nbsp;&nbsp;&nbsp;&nbsp;3 Years | $&nbsp;&nbsp;&nbsp;&nbsp; 763 | $&nbsp;&nbsp;&nbsp;&nbsp; 757 | $&nbsp;&nbsp;&nbsp;&nbsp; 603 | $&nbsp;&nbsp;&nbsp;&nbsp; 903 | $&nbsp;&nbsp;&nbsp;&nbsp; 603 | $&nbsp;&nbsp;&nbsp;&nbsp; 603 | $&nbsp;&nbsp;&nbsp;&nbsp; 241 | $&nbsp;&nbsp;&nbsp;&nbsp; 359 | $&nbsp;&nbsp;&nbsp;&nbsp; 437 | $&nbsp;&nbsp;&nbsp;&nbsp; 208 |
| &nbsp;&nbsp;&nbsp;&nbsp;5 Years | $&nbsp;&nbsp;&nbsp;&nbsp; 993 | $1018 | $1037 | $1237 | $1037 | $1037 | $&nbsp;&nbsp;&nbsp;&nbsp; 425 | $&nbsp;&nbsp;&nbsp;&nbsp; 622 | $&nbsp;&nbsp;&nbsp;&nbsp; 755 | $&nbsp;&nbsp;&nbsp;&nbsp; 362 |
| &nbsp;&nbsp;&nbsp;&nbsp;10 Years | $1653 | $1764 | $2048 | $2048 | $2048 | $2048 | $&nbsp;&nbsp;&nbsp;&nbsp; 959 | $1375 | $1657 | $&nbsp;&nbsp;&nbsp;&nbsp; 810 |

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**Portfolio Turnover**

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 86% of the average value of its portfolio.

**Principal Investment Strategies**

The Fund seeks to achieve its investment objective through a flexible investment process that allocates investments across the global fixed-income markets. The Fund, under normal circumstances, invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in a diversified portfolio of debt or debt-related securities such as: debt or debt-related securities issued or guaranteed by the U.S. or foreign governments, their agencies or instrumentalities; obligations of international or supranational entities; debt or debt-related securities issued by U.S. or foreign corporate entities; zero coupon bonds; municipal bonds; mortgage-related and other asset-backed securities; loan participation interests; convertible bonds; and variable or floating rate debt securities. The Fund may invest in debt securities that are rated investment grade and below investment grade by a nationally recognized statistical rating organization ("NRSRO") (such securities rated lower than BBB- and Baa3). Securities that are rated below investment grade by NRSROs are commonly referred to as "high-yield securities" or "junk bonds." 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 securities may be denominated in U.S. or foreign currencies, and may have fixed, variable, floating or inverse floating rates of interest. The Fund may invest without limitation in securities of foreign issuers, including emerging markets. An issuer of a security is considered to be a U.S. or foreign issuer based on the issuer's "country of risk" (or similar designation) as determined by a third-party such as Bloomberg. The currency exposure of non-U.S. investments may or may not be hedged. The Fund may invest up to 15% of its net assets in equity securities.

The Fund intends to utilize various investment strategies in a broad array of fixed-income sectors to achieve its investment objective. The Fund will not be constrained by portfolio management relative to an index. Because the Fund does not track a fixed-income index, its performance may vary at times and demonstrate low correlation to traditional fixed-income indices. In pursuing its investment objective, the Fund's investment strategy is subject to market risk and shares may gain or lose value.

The average portfolio duration of the Fund will normally vary from 0 to 7 years. Duration is a measure used to determine the sensitivity of a security's price to changes in interest rates. The longer a security's duration, the more sensitive it will be to changes in interest rates.

The Fund may invest in derivatives, such as futures, options, forward commitments and interest rate swap agreements to try to enhance returns or reduce the risk of loss by hedging certain of its holdings or manage duration. The Fund may invest up to 25% of its total assets in swaps.

The Fund may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The Fund's short positions, either direct short positions or through credit default swaps or total return swaps, may total up to 20% of the Fund's net assets. The Fund may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

**Investment Process:** MacKay Shields LLC, the Fund's Subadvisor, seeks to identify investment opportunities through an investment process focused on macroeconomic analysis and bottom-up security selection. The Subadvisor allocates the Fund's investments among the various bond market sectors based on current and projected economic and market conditions. The Fund may invest across bond market sectors, geographies and credit qualities.

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 no sectors or industries are explicitly excluded from the Fund.

The Subadvisor may sell a security if it believes the security will no longer 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 domestic and foreign economies, and meaningful changes in the issuer's financial condition, including changes in the issuer's credit risk and competitiveness.

**Principal Risks** 

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:** Changes in markets may cause the value of investments to fluctuate, 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 as a result

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of various market and economic factors for potentially prolonged periods that may result in: (i) increased market volatility; (ii) reduced market liquidity; and (iii) increased redemptions of 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 or expected returns. 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.

**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. Low interest rates (or negative interest rates) may magnify the risks associated with rising interest rates. The Fund may also be subject to heightened interest rate risk when the Federal Reserve raises interest rates. 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.

**Zero Coupon Bond Risk:** Because zero-coupon securities bear no interest and compound semi-annually at the rate fixed at the time of issuance, their value generally is more volatile than the value of other fixed-income securities. An investment in zero-coupon and delayed interest securities may cause the Fund to recognize income, and therefore the Fund may be required to make distributions to shareholders before the Fund receives any cash payments on its investment.

**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. Municipalities continue to experience 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.

**Short Selling and Short Exposure Risk:** To the extent the Fund obtains short exposure through the use of derivatives, the Fund would be subject to leverage risk, counterparty risk and other risks associated with the use of derivatives. If a security sold short increases in price, the Fund may have to cover its short position at a higher price than the short sale price, resulting in a loss, which could be theoretically unlimited. By contrast, a loss on a long position arises from decreases in the value of the security and is limited by the fact that a security's value cannot go below zero. The Fund may have substantial short positions and must borrow those securities to make delivery to the buyer. The Fund may not be able to borrow a security that it needs to deliver or it may not be able to close out a short position at an acceptable price and may have to sell related long positions before it had intended to do so. Thus, the Fund may not be able to successfully implement its short sale strategy due to limited availability of desired securities or for other reasons. The Fund also may be required to pay a premium and other transaction costs, which would increase the cost of the security sold short. The amount of any gain will be decreased, and the amount of any loss increased, by the amount of the premium, dividends, interest or expenses the Fund may be required to pay in connection with the short sale.

Until the Fund replaces a borrowed security, it is required to maintain a segregated account of cash or liquid assets with the Fund's broker or custodian to cover the Fund's short position. Generally, securities held in a segregated account cannot be sold unless they are replaced with other liquid assets. The Fund's ability to access the pledged collateral may also be impaired in the event the broker fails to comply with the terms of the contract. In such instances the Fund may not be able to substitute or sell the pledged collateral. This may limit the Fund's investment flexibility, as well as its ability to meet redemption requests or other current obligations.

By investing the proceeds received from selling securities short, the Fund could be deemed to be employing a form of leverage, which creates special risks. The use of leverage may increase the Fund's exposure to long positions and make any change in the Fund's net asset value greater than it would be without the use of leverage. This could result in increased volatility of returns. There is no guarantee that the Fund will leverage its portfolio, or if it does, that the Fund's leveraging strategy will be successful or that it will produce a higher return on an investment.

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**Regulatory Risk:** The Fund as well as the issuers of the securities and other instruments in which the Fund invests are subject to considerable regulation and the risks associated with adverse changes in laws and regulations governing their operations. For example, regulatory authorities in the United States or other countries may prohibit or restrict the ability of the Fund to short sell certain securities, either generally or with respect to certain industries or countries, which may impact the Fund's ability to fully implement its investment strategies.

**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 be riskier than investing 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. Forward commitments entail the risk that the instrument may be worth less when it is issued or received than the price the Fund agreed to pay when it made the commitment. The use of foreign currency forwards may result in currency exchange losses due to fluctuations in currency exchange rates or an imperfect correlation between portfolio holdings denominated in a particular currency and the forward contracts entered into by the Fund. 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.

**High-Yield Securities Risk:** Investments in high-yield securities or non-investment grade securities (commonly referred to as "junk bonds") are considered speculative because investments in such securities present a greater risk of loss than investments in higher quality securities. Such securities may, under certain circumstances, be less liquid than higher rated securities. These securities pay investors a premium (a high interest rate or yield) because of the potential illiquidity and increased risk of loss. These securities can also be subject to greater price volatility. In times of unusual or adverse market, economic or political conditions, these securities may experience higher than normal default rates.

**Floating Rate Notes and Variable Rate Notes Risk:** Floating and variable rate notes provide for a periodic adjustment in the interest rate paid on the securities. The rate adjustment intervals may be regular and range from daily up to annually, or may be based on an event, such as a change in the prime rate. Floating and variable rate notes may be subject to greater liquidity risk than other debt securities, meaning that there may be limitations on the Fund's ability to sell the securities at any given time. Securities with floating interest rates generally are less sensitive to interest rate changes, but may decline in value if their interest rates do not rise as much or as fast as interest rates in general. Floating rate loans and other similar debt obligations that lack financial maintenance covenants or possess fewer or contingent financial maintenance covenants and other financial protections for lenders and investors (sometimes referred to as "covenant-lite" loans or obligations) are generally subject to more risk than investments that contain traditional financial maintenance covenants and financial reporting requirements. The terms of many floating rate notes and other instruments are tied to the London Interbank Offered Rate ("LIBOR") or the Secured Overnight Financing Rate ("SOFR"), which function as reference rates or benchmarks. Certain LIBOR tenors were discontinued at the end of 2021, but the most widely used LIBOR tenors may continue to be provided on a representative basis until mid-2023. There remains uncertainty regarding the future use of LIBOR and the nature of any replacement rate, such as SOFR. As such, the potential effect of a transition away from LIBOR tenors may cause increased volatility and illiquidity in the markets for instruments with terms tied to such LIBOR tenors or other adverse consequences, such as decreased yields and reduction in value, for these instruments. This may adversely affect the Fund and its investments in such instruments.

**Mortgage Dollar Roll Transaction Risk:** A mortgage dollar roll is a transaction in which the Fund sells mortgage-related securities from its portfolio to a counterparty from whom it simultaneously agrees to buy a similar security on a delayed delivery basis. Mortgage dollar roll transactions are subject to certain risks, including the risk that securities returned to the Fund at the end of the roll, while substantially similar, may be inferior to what was initially sold to the counterparty.

**Mortgage-Related and Other Asset-Backed Securities Risk:** Investments in mortgage-related securities (such as mortgage-backed securities) and other asset-backed securities generally involve a stream of payments based on the underlying obligations. These payments, which are often part interest and part return of principal, vary based on the rate at which the underlying borrowers repay their loans or other obligations. Asset-backed securities are subject to the risk that borrowers may default on the underlying obligations and that, during periods of falling interest rates, these obligations may be called or prepaid and, during periods of rising interest rates, obligations may be paid more slowly than expected. Impairment of the underlying obligations or collateral, such as by non-payment, will reduce the security's value. Enforcing rights against such collateral in events of default may be difficult or insufficient. The value of these securities may be significantly affected by changes in interest rates, the market's perception of issuers, and the creditworthiness of the parties involved. The ability of the Fund to successfully utilize these instruments may depend on the ability of the Subadvisor to forecast interest rates and other economic factors correctly. These securities may have a structure that makes their reaction to interest rate changes and other factors difficult to predict, making their value highly volatile.

**Loan Participation Interest Risk:** There may not be a readily available market for loan participation interests, which in some cases could result in the Fund disposing of such interests at a substantial discount from face value or holding such interests until maturity. In addition, the Fund may be exposed to the credit risk of the underlying corporate borrower as well as the lending institution or other participant from whom the Fund purchased the loan participation

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interests. The Fund may not always have direct recourse against a borrower if the borrower fails to pay scheduled principal and/or interest and may be subject to greater delays, expenses and risks than if the Fund had purchased a direct obligation of the borrower. Substantial increases in interest rates may cause an increase in loan obligation defaults.

**Floating Rate Loans Risk:** The floating rate loans in which the Fund invests are usually rated below investment grade, or if unrated, determined by the Subadvisor to be of comparable quality (commonly referred to as "junk bonds") and are generally considered speculative because they present a greater risk of loss, including default, than higher quality debt instruments. Moreover, such investments may, under certain circumstances, be particularly susceptible to liquidity and valuation risks. Although certain floating rate loans are collateralized, there is no guarantee that the value of the collateral will be sufficient or available to satisfy the borrower's obligation. In times of unusual or adverse market, economic or political conditions, floating rate loans may experience higher than normal default rates. In the event of a recession or serious credit event, among other eventualities, the value of the Fund's investments in floating rate loans are more likely to decline. The secondary market for floating rate loans is limited and, thus, the Fund's ability to sell or realize the full value of its investment in these loans to reinvest sale proceeds or to meet redemption obligations may be impaired. In addition, floating rate loans generally are subject to extended settlement periods that may be longer than seven days. As a result, the Fund may be adversely affected by selling other investments at an unfavorable time and/or under unfavorable conditions or engaging in borrowing transactions, such as borrowing against its credit facility, to raise cash to meet redemption obligations or pursue other investment opportunities.

In certain circumstances, floating rate loans may not be deemed to be securities. As a result, the Fund may not have the protection of the anti-fraud provisions of the federal securities laws. In such cases, the Fund generally must rely on the contractual provisions in the loan agreement and common-law fraud protections under applicable state law.

Floating rate loans and other similar debt obligations that lack financial maintenance covenants or possess fewer or contingent financial maintenance covenants and other financial protections for lenders and investors (sometimes referred to as "covenant-lite" loans or obligations) are generally subject to more risk than investments that contain traditional financial maintenance covenants and financial reporting requirements.

The terms of many floating rate loans and other instruments are tied to the London Interbank Offered Rate ("LIBOR") or the Secured Overnight Financing Rate ("SOFR"), which function as reference rates or benchmarks. Certain LIBOR tenors were discontinued at the end of 2021, but the most widely used LIBOR tenors may continue to be provided on a representative basis until mid-2023. There remains uncertainty regarding the future use of LIBOR and the nature of any replacement rate, such as SOFR. As such, the potential effect of a transition away from LIBOR tenors may cause increased volatility and illiquidity in the markets for instruments with terms tied to such LIBOR tenors or other adverse consequences, such as decreased yields and reduction in value, for these instruments. This may adversely affect the Fund and its investments in such instruments.

**Foreign Securities Risk:** Investments in foreign (non-U.S.) securities may be riskier than investments in U.S. securities. Foreign regulatory regimes and securities markets can have less stringent investor protections and disclosure standards and less liquid trading markets than U.S. regulatory regimes and securities markets, and can experience political, social and economic developments that may affect the value of investments in foreign securities. Foreign securities may also subject the Fund's investments to changes in currency rates. Changes in the value of foreign currencies may make the return on an investment increase or decrease, unrelated to the quality or performance of the investment itself. Economic sanctions may be, and have been, imposed against certain countries, organizations, companies, entities and/or individuals. Economic sanctions and other similar governmental actions or developments could, among other things, effectively restrict or eliminate the Fund's ability to purchase or sell certain foreign securities or groups of foreign securities, and thus may make the Fund's investments in such securities less liquid or more difficult to value. Such sanctions may also cause a decline in the value of securities issued by the sanctioned country or companies located in or economically tied to the sanctioned country. In addition, as a result of economic sanctions and other similar governmental actions or developments, the Fund may be forced to sell or otherwise dispose of foreign investments at inopportune times or prices. The Fund may seek to hedge against its exposure to changes in the value of foreign currency, but there is no guarantee that such hedging techniques will be successful in reducing any related foreign currency valuation risk. These risks may be greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets.

**Emerging Markets Risk:** The risks related to investing in foreign securities are generally greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets. The risks of investing in emerging markets are elevated under current conditions and include: (i) smaller trading volumes for such securities and limited access to investments in the event of market closures (including due to local holidays), which result in a lack of liquidity and in greater price volatility; (ii) less government regulation, which could lead to market manipulation, and less extensive, transparent and frequent accounting, auditing, recordkeeping, financial reporting and other requirements, which limit the quality and availability of financial information; (iii) the absence of developed legal systems, including structures governing private or foreign investment or allowing for judicial redress (such as limits on rights and remedies available) for investment losses and injury to private property; (iv) loss resulting from problems in share registration and custody; (v) sensitivity to adverse political or social events affecting the region where an emerging market is located; (vi) particular sensitivity to economic and political disruptions, including adverse effects stemming from wars, sanctions, trade restrictions, recessions, depressions or other economic crises, or reliance on international or other forms of aid, including trade, taxation and development policies; and (vii) the nationalization of foreign deposits or assets.

**Convertible Securities Risk:** Convertible securities are typically subordinate to an issuer's other debt obligations. In part, the total return for a convertible security depends upon the performance of the underlying stock into which it can be converted. Also, issuers of convertible securities are often not as strong financially as those issuing securities with higher credit ratings, are more likely to encounter financial difficulties and typically are more vulnerable to changes in the economy, such as a recession or a sustained period of rising interest rates, which could affect their ability to make interest and principal payments. If an issuer stops making interest and/or principal payments, the Fund could lose its entire investment.

**Equity Securities Risk:** Investments in common stocks and other equity securities are particularly subject to the risk of changing economic, stock market, industry and company conditions and the risks inherent in the ability to anticipate such changes that can adversely affect the value of portfolio holdings.

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**When-Issued Securities Risk:** The Fund may agree to purchase a security on a when-issued basis, making a commitment to pay a fixed price for a security when it is issued in the future. The principal risk of transactions involving when-issued securities is that the security will be worth less when it is issued or received than the price the Fund agreed to pay when it made the commitment.

**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 when interest rates are low or rapidly increasing.

**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.

**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.

**Past Performance**

The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns compare with those of a broad-based securities market index as well as two additional benchmarks over time. Sales loads, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. The Fund has selected the Bloomberg U.S. Aggregate Bond Index as its primary benchmark. The Fund has selected the ICE BofA U.S. Dollar 3-Month Deposit Offered Rate Constant Maturity Index as its secondary benchmark. The Fund has selected the Morningstar Nontraditional Bond Category Average as an additional benchmark.

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

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.

Effective February 28, 2013, the Fund's investment objective and principal investment strategies changed. The performance in the bar chart and table prior to that date reflects the Fund's prior investment objective and principal investment strategies.

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#### Annual Returns, Class I Shares

#### (by calendar year 2013-2022)
![PerformanceBarChartData(2013:4.14, 2014:1.35, 2015:-3.56, 2016:8.28, 2017:4.95, 2018:-1.57, 2019:6.82, 2020:6.44, 2021:2.2, 2022:-7.47)](img_3392bcef96674f1.jpg)

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| | |
|:---|:---|
| **Best Quarter** | **Best Quarter** |
| 2020, Q2 | 7.20% |
| **Worst Quarter** | **Worst Quarter** |
| 2020, Q1 | -7.38% |

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**Average Annual Total Returns** (for the periods ended December 31, 2022)

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| | | | | |
|:---|:---|:---|:---|:---|
| | <br>Inception<br>| <br>&nbsp;&nbsp;&nbsp;&nbsp; 1 Year<br> | <br>5 Years<br> | 10 Years or<br>Since<br>Inception |
| Return Before Taxes |  |  |  |  |
| &nbsp;&nbsp;&nbsp;Class I | 1/2/2004 | -7.47% | 1.14% | 2.04% |
| Return After Taxes on Distributions |  |  |  |  |
| &nbsp;&nbsp;&nbsp;Class I |  | -8.75% | -0.05% | 0.60% |
| Return After Taxes on Distributions and Sale of Fund Shares |  |  |  |  |
| &nbsp;&nbsp;&nbsp;Class I |  | -4.42% | 0.38% | 0.92% |
| Return Before Taxes |  |  |  |  |
| &nbsp;&nbsp;&nbsp;Class A | 2/28/1997 | -11.95% | -0.08% | 1.31% |
| &nbsp;&nbsp;&nbsp;Investor Class | 2/28/2008 | -11.55% | -0.15% | 1.25% |
| &nbsp;&nbsp;&nbsp;Class B | 2/28/1997 | -13.05% | -0.35% | 0.95% |
| &nbsp;&nbsp;&nbsp;Class C | 9/1/1998 | -9.47% | 0.02% | 0.96% |
| &nbsp;&nbsp;&nbsp;Class R2 | 2/28/2014 | -7.88% | 0.79% | 1.31% |
| &nbsp;&nbsp;&nbsp;Class R3 | 2/29/2016 | -8.01% | 0.50% | 2.43% |
| &nbsp;&nbsp;&nbsp;Class R6 | 2/28/2018 | -7.41% | N/A | 1.43% |
| Bloomberg U.S. Aggregate Bond Index<sup>1</sup> | Bloomberg U.S. Aggregate Bond Index<sup>1</sup> | -13.01% | 0.02% | 1.06% |
| ICE BofA U.S. Dollar 3-Month Deposit Offered Rate Constant Maturity Index<sup>2</sup> | ICE BofA U.S. Dollar 3-Month Deposit Offered Rate Constant Maturity Index<sup>2</sup> | 1.21% | 1.43% | 0.96% |
| Morningstar Nontraditional Bond Category Average<sup>3</sup> | Morningstar Nontraditional Bond Category Average<sup>3</sup> | -6.38% | 0.69% | 1.21% |

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1. The Bloomberg U.S. Aggregate Bond Index is a broad-based benchmark that measures the investment grade, U.S. dollar-denominated, fixed-rate taxable bond market, including Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate and hybrid adjustable rate mortgage pass-throughs), asset-backed securities and commercial mortgage-backed securities.

2. The ICE BofA U.S. Dollar 3-Month Deposit Offered Rate Constant Maturity Index is unmanaged and tracks the performance of a synthetic asset paying a deposit offered rate to a stated maturity. The ICE BofA U.S. Dollar 3-Month Deposit Offered Rate Constant Maturity Index is based on the assumed purchase at par of a synthetic instrument having exactly its stated maturity and with a coupon equal to that day's fixing rate. That issue is assumed to be sold the following business day (priced at a yield equal to the current day fixing rate) and rolled into a new instrument.

3. The Morningstar Nontraditional Bond Category Average contains funds that pursue strategies divergent in one or more ways from conventional practice in the broader bond-fund universe. Morningstar category averages are equal-weighted returns based on constituents of the category at the end of the period.

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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.

**Management**

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

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| | | |
|:---|:---|:---|
| **Subadvisor** | **Portfolio Managers** | **Service Date** |

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| | | |
|:---|:---|:---|
| MacKay Shields LLC | Stephen R. Cianci, Senior Managing Director | Since 2018 |
|  | Shu-Yang Tan, Managing Director | Since 2018 |
|  | Matt Jacob, Managing Director | Since 2018 |
|  | Neil Moriarty, III, Senior Managing Director | Since 2018 |
|  | Lesya Paisley, Director | Since 2022 |

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**How to Purchase and Sell Shares**

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 430 West 7<sup>th</sup> 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 $1,000 applies if you invest in Investor Class or Class C 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 and Class C shares. However, for Investor Class and Class C shares purchased through AutoInvest, MainStay's systematic investment plan, a $500 initial investment minimum and a $50 minimum for subsequent purchases applies. Class A shares have no subsequent investment minimum. Class R2 shares, Class R3 shares, Class R6 shares and institutional shareholders in Class I shares have no initial or subsequent investment minimums. Class B shares are closed to all new purchases and additional investments by existing Class B shareholders.

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.

**Tax Information**

The Fund's distributions are generally taxable to you as ordinary income, capital gains, or a combination of the two, unless you are investing through a tax-deferred arrangement, such as a 401(k) plan or an individual retirement account.

**Compensation to Financial Intermediary Firms**

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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