The fund’s investment objective is to seek a high level of total return consistent with its asset allocation until the approximate retirement year in the fund's name; thereafter, the fund will seek total return through a combination of current income and capital appreciation. The asset allocation of the fund will change over time.

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

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 shares are held in a taxable account. These transaction 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 8% of the average value of its portfolio.

The fund is designed to provide diversification among different asset classes for investors with the approximate retirement year in the fund's name. MFS (Massachusetts Financial Services Company, the fund's investment adviser) invests substantially all of the fund's assets in other MFS mutual funds, referred to as underlying funds.

MFS selects the asset class allocations based on a strategic asset allocation process that takes into account a variety of factors, including historical risk and performance, projected performance, and other factors. MFS’ analyses of projected performance are primarily based on quantitative models using various inputs such as valuation metrics, growth rates, profitability, yields, and inflation. MFS may also consider current market conditions, its qualitative assessment of the risk/return characteristics of asset classes, and other factors in determining these allocations.

MFS employs the strategic asset allocation process described above to determine the amount of the fund's assets invested in (1) underlying funds that invest primarily in equity securities (“Equity Funds”) and underlying funds that provide exposure to less traditional asset classes, currently real estate and commodities (“Non-Traditional Funds”) and (2) underlying funds that invest primarily in debt instruments (“Bond Funds”) and an underlying fund that invests in cash and/or cash equivalents (“Money Market Fund”).

MFS selects the underlying funds within each asset class based on underlying fund classifications, historical risk, historical and projected performance of the represented asset classes, as well as other factors.

Within the Equity Fund allocation, MFS seeks to diversify by geography (by including domestic and international underlying funds, including emerging market underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds) and by style (by including both growth and value underlying funds). A portion of the fund’s assets is also allocated to Non-Traditional Funds (i.e., asset classes less correlated to the overall equity and debt markets), which MFS believes provides further diversification benefits.

Within the Bond Fund allocation, MFS includes underlying funds with varying degrees of geographic (potentially including emerging market), interest rate and credit exposure, including exposure to below investment grade quality debt instruments. A portion of the fund’s assets may also be allocated to the Money Market Fund.

MFS normally invests the underlying funds’ assets across different industries, sectors, countries, and regions, but MFS may invest a significant percentage of the underlying funds' assets in issuers in a single industry, sector, country, or region.

As of August 1, 2026, the fund’s approximate long-term strategic allocation among asset classes was:

All percentages are rounded to the nearest percent.

MFS may deviate from the long-term strategic allocations set forth above; however, any deviation from the long-term strategic allocation is not expected to be greater than plus or minus 10% under normal market conditions. At no time, however, will the fund’s investments in Equity Funds and Non-Traditional Funds exceed 99%. Additionally, the fund’s allocation to Non-Traditional Funds will not typically exceed 20% of the fund’s assets.

As of August 1, 2026, the fund’s approximate strategic allocation among asset classes was:

All percentages are rounded to the nearest tenth of a percent. As a result, the sum of the asset class allocations presented in the table may not total 100%.

The asset class allocations for the fund, as well as the underlying funds and their weightings, are based on an allocation strategy designed for investors with the approximate retirement year in the fund’s name. Investors should also consider their age, personal circumstances, risk tolerance, and overall investment strategy and

allocation. The asset allocation strategy will become increasingly conservative over time, shifting more weight from Equity Funds and Non-Traditional Funds to Bond Funds and the Money Market Fund.

Upon reaching its stated target year, the fund’s allocation strategy will be aligned with the allocation strategy of MFS Lifetime Income Fund. It is expected that the fund will be combined with MFS Lifetime Income Fund within five years of the date that its asset allocation strategy matches the asset allocation strategy of MFS Lifetime Income Fund. MFS Lifetime Income Fund is designed for investors who intend to withdraw assets over an extended period of time or who want an investment with an asset allocation mix similar to MFS Lifetime Income Fund's long-term strategic asset allocation. The chart below illustrates how the asset allocation strategy of the fund will change over time.

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of (i) a broad measure of market performance and (ii) the performance of an additional index that the adviser believes more closely reflects the market segments in which the fund invests.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

As of December 31, 2025, the MFS Lifetime 2045 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 12.75% Bloomberg U.S. Aggregate Bond Index; 54.42% Standard & Poor's 500 Stock Index; 23.87% MSCI EAFE Index (net div); 4.48% Bloomberg Commodity Index; and 4.48% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (IRAs). The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund, including near or after the target year. There is no guarantee that the fund will provide income at or through retirement. 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 principal risks of investing in the fund are:

Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes the fund to the risks of the underlying funds. Each underlying fund pursues its own investment objective and strategies and may not achieve its objective. In addition to the fees and expenses the fund bears directly, shareholders of the fund will indirectly bear the fees and expenses of the underlying funds.

Equity Market Risk/Company Risk: Equity markets are volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general. Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market. The value of an investment held by the fund may decline due to factors directly related to the issuer.

Value Company Risk: The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Interest Rate Risk: In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities or durations, or that do not pay current interest.

Prepayment/Extension Risk: Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Focus Risk: Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed. Furthermore, investments in particular industries, sectors, countries, or regions may be more volatile than the broader market as a whole.

Emerging Markets Risk: Investments tied economically to emerging markets, especially frontier markets, can involve additional and greater risks than the risks associated with investments in developed markets. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, greater government involvement in the economy, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater political, social, geopolitical, and economic instability than developed markets.

Real Estate-Related Investment Risk: The risks of investing in real estate-related securities include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; difficulties in valuing and disposing of real estate; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; the management skill and creditworthiness of the real estate investment trust (REIT) manager; and other factors. The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

When-Issued, Delayed Delivery, and Forward Commitment Transaction Risk: The purchaser in a when-issued, delayed delivery or forward commitment transaction assumes the rights and risks of ownership, including the risks of price and yield fluctuations and the risk that the security will not be issued or delivered as anticipated. When-issued, delayed delivery, and forward commitment transactions can involve leverage. To be announced (TBA) transactions may significantly increase the fund's portfolio turnover rate.

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.