Investments

The fund is one of a series of target date funds that invest primarily in exchange-traded funds (“ETFs”) that focus on investments with positive sustainability or environmental, social, and governance (“ESG”) characteristics, referred to as underlying funds. The underlying funds are sponsored by Putnam Investment Management, LLC (“Putnam Management”) and advised by Putnam Management. Two underlying funds are subadvised by Putnam Management’s affiliate, PanAgora Asset Management, Inc. (“PanAgora”). The fund’s asset allocation strategy may be attractive to investors who plan to retire or otherwise intend to begin making periodic withdrawals of their investments in or about 2055 (the target date). The fund is designed to provide diversification among different asset classes by investing its assets in the underlying funds.

Under normal circumstances, the fund will invest in underlying funds (which, for purposes of this policy, include money market mutual funds advised by Putnam Management or its affiliates) such that, in the aggregate, it has indirect exposure to investments that meet Putnam Management’s or PanAgora’s, as applicable, sustainability or ESG criteria and that represent at least 80% of the value of its net assets. This policy is non-fundamental and may be changed only after 60 days’ notice to shareholders. Putnam Management may not apply ESG or sustainability criteria

to investments that are not subject to the fund’s 80% policy, and such investments may not meet the applicable ESG or sustainability criteria. The fund, through its investments in underlying funds, makes use of a range of ESG- and sustainability- oriented investment strategies and invests across of variety of asset classes. For example, Putnam Management’s sustainability criteria for the investments of Putnam Sustainable Leaders ETF and Putnam Sustainable Future ETF (two of the underlying funds that invest primarily in equities) differ from the ESG approach used by Putnam Management for the fixed-income underlying funds, and from PanAgora’s quantitatively-oriented ESG equity approach for the underlying funds that it subadvises. These differences may arise both from differences in the underlying funds’ asset classes (such as the characteristics of non-U.S. versus U.S. issuers, or the structural differences (i.e., position in the capital structure) between equity and fixed-income investments) as well as from different managers’ styles. In implementing an underlying fund’s investment strategy, the portfolio managers of the underlying fund may apply and weigh different ESG criteria differently than the portfolio managers of the other underlying funds. There are also expected to be differences in how the portfolio managers of the underlying funds source ESG-related or sustainability-oriented research (e.g., proprietary versus third-party research) and/or their approach to selecting companies based on ESG or sustainability criteria.

The fund’s target allocations among asset classes and underlying funds will increasingly emphasize capital preservation and income over time and will change gradually based on the number of remaining years until the fund’s target date, as shown in the predetermined “glide path” in the chart under “What are the funds’ and each underlying fund’s main investment strategies and related risks?” Putnam Management adjusts these allocations at the end of each calendar quarter based on the glide path.

Pending investment in underlying funds, the fund also expects to temporarily invest cash balances resulting from purchase activity by fund shareholders in Putnam Government Money Market Fund, a mutual fund sponsored by Putnam Management, or in cash or cash equivalents. The fund also expects to invest a portion of its assets in Putnam Government Money Market Fund or in cash or cash equivalents in order to manage shareholder redemptions. The percentage of a fund invested in Putnam Government Money Market Fund is expected to vary over time and will depend on the level of purchase and redemption activity by fund shareholders.

The following table presents your fund’s approximate allocations to each asset class and underlying fund as of September 30, 2023 (taking into account any tactical adjustments described below) and its projected approximate allocations to those asset classes and underlying funds as of September 30, 2024. The table does not reflect temporary investments in Putnam Government Money Market Fund or in cash or cash equivalents. By comparing the percentage allocations of your fund in the table, you can see how its allocations are expected to change during the one-year period beginning on September 30, 2023. The table also shows the approximate allocations of other Putnam Sustainable Retirement Funds, which are designed for

investors with different target retirement dates. Over a five-year period, each fund’s allocations will gradually change to resemble the allocations of the fund with the next earliest target date. The table illustrates how a fund’s allocations are expected to change over time to increasingly emphasize capital preservation and income.

The fund’s target allocations may differ from the allocations shown in the table. Putnam Management may change the glide path, the fund’s target allocations, and the underlying funds in which it invests at any time, although Putnam Management generally expects these changes (other than the tactical adjustments described below) to be infrequent and generally in response to longer-term structural changes

(i.e., in the average retirement age or life expectancy) that lead the fund’s portfolio managers to determine that a change is advisable. Putnam Management may also make tactical adjustments from time to time in the fund’s allocations to underlying funds in response to market conditions within a range of +/- 15% from the allocations to fixed-income and equity asset classes as presented in the fund’s glide path.

It is assumed that investors will begin gradual withdrawals from the fund at around the target date. Near the end of the target date year, the fund’s target allocations will correspond to those of Putnam Sustainable Retirement Maturity Fund (Maturity Fund), a fund that seeks as high a rate of current income as Putnam Management believes is consistent with preservation of capital, and the fund will be merged into Maturity Fund. More information about Maturity Fund is available in the prospectus beginning on page 164, and more information about the underlying funds (which are not offered by this prospectus) is included below and under “What are the funds’ and each underlying fund’s main investment strategies and related risks?”

Information about each underlying fund’s investment strategy

Putnam Sustainable Leaders ETF (“Sustainable Leaders ETF”)

Sustainable Leaders ETF invests mainly in common stocks of U.S. companies of any size, with a focus on companies that Putnam Management believes exhibit a commitment to financially material sustainable business practices. Sustainable Leaders ETF may also invest in non-U.S. companies. In evaluating investments for Sustainable Leaders ETF, Putnam Management views “financially material sustainable business practices” as business practices that it believes are reasonably likely to impact the financial condition or operating performance of a company and that relate to environmental, social, or corporate governance issues.

Under normal circumstances, Sustainable Leaders ETF invests at least 80% of the value of its net assets in securities that meet Putnam Management’s sustainability criteria. For a further discussion of Sustainable Leaders ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam Sustainable Future ETF (“Sustainable Future ETF”)

Sustainable Future ETF invests mainly in common stocks of U.S. companies of any size, with a focus on companies whose products and services Putnam Management believes provide solutions that directly contribute to sustainable social, environmental and economic development (Solutions Companies).

Under normal circumstances, Sustainable Future ETF invests at least 80% of the value of its net assets in securities that meet Putnam Management’s sustainability criteria. For a further discussion of Sustainable Future ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam PanAgora ESG International Equity ETF (“PanAgora International Equity ETF”)

PanAgora International Equity ETF invests mainly in common stocks (growth or value stocks or both) of companies of any size outside the United States with a focus on companies that PanAgora International Equity ETF’s subadviser, PanAgora, believes offer attractive benchmark-relative returns and exhibit positive ESG metrics. Under normal circumstances, PanAgora International Equity ETF invests at least 80% of its net assets in equity securities of companies that meet PanAgora’s ESG criteria. For a further discussion of PanAgora International Equity ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam PanAgora ESG Emerging Markets Equity ETF (“PanAgora Emerging Markets Equity ETF”)

PanAgora Emerging Markets Equity ETF invests mainly in common stocks (growth or value stocks or both) of emerging markets companies of any size with a focus on companies that PanAgora Emerging Markets Equity ETF’s subadviser, PanAgora, believes offer attractive benchmark-relative returns and exhibit positive ESG metrics. Under normal circumstances, PanAgora Emerging Markets Equity ETF invests at least 80% of its net assets in equity securities of emerging markets companies that meet PanAgora’s ESG criteria. For a further discussion of PanAgora Emerging Markets Equity ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam ESG Core Bond ETF (“Core Bond ETF”)

Core Bond ETF invests mainly in a diversified portfolio of investment-grade fixed-income securities with a focus on companies or issuers that Putnam Management, Core Bond ETF’s investment manager, believes meet relevant ESG criteria on a sector-specific basis. Under normal circumstances, Core Bond ETF invests at least 80% of the value of its net assets in fixed-income securities that meet Putnam Management’s ESG criteria. For a further discussion of Core Bond ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam ESG High Yield ETF (“High Yield ETF”)

High Yield ETF invests mainly in bonds that are below investment grade in quality (sometimes referred to as “junk bonds”) with a focus on companies or issuers that Putnam Management, High Yield ETF’s investment manager, believes meet relevant ESG criteria on a sector-specific basis. High Yield ETF invests mainly in bonds that also have one or more of the following characteristics: (1) are obligations of U.S. companies or issuers and (2) have intermediate- to long-term maturities (three years or longer). Under normal circumstances, High Yield ETF invests at least 80% of the value of its net assets in fixed-income securities rated below investment grade that meet Putnam Management’s ESG criteria. For a further discussion of High Yield ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.

Putnam ESG Ultra Short ETF (“Ultra Short ETF”)

Ultra Short ETF invests in a diversified short duration portfolio of fixed-income securities comprised of investment-grade money market and other fixed-income securities, including U.S. dollar-denominated foreign securities of these types, with a focus on companies or issuers that Putnam Management believes meet relevant ESG criteria, on a sector-specific basis. Under normal circumstances, Ultra Short ETF invests at least 80% of the value of its net assets in fixed-income securities that meet Putnam Management’s ESG criteria. For a further discussion of Ultra Short ETF’s investment strategy, please turn to the section What are the funds’ and each underlying fund’s main investment strategies and related risks? beginning on page 182.