v3.25.2
Investment Strategy
Apr. 30, 2025
MFS Core Bond Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in debt instruments. Debt instruments include corporate bonds, U.S. Government securities, securitized instruments (including mortgage-backed securities and other asset-backed securities), and other obligations to repay money borrowed.

MFS generally invests substantially all of the fund’s assets in investment grade quality debt instruments.

MFS may purchase or sell securities for the fund on a when-issued, delayed delivery, or forward commitment basis where payment and delivery take place at a future settlement date, including mortgage-backed securities purchased or sold in the TBA market.

MFS may invest the fund’s assets in foreign securities.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS may invest a significant percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, and swaps.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative screening tools that systematically evaluate instruments may also be considered. In structuring the fund, MFS also considers top-down factors.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

MFS Lifetime Income Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

The fund is designed to provide diversification among different asset classes by investing the majority of its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's investment adviser), 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, such as 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), 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, 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.

The 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 the fund's long-term strategic asset allocation.

As of August 1, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

29%

Bond Funds and Money Market Fund

71%

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. Additionally, the fund’s allocation to Non-Traditional Funds will not typically exceed 20% of the fund’s assets.

As of August 1, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

29.0%

U.S. Equity Funds

20.0%

International Equity Funds

5.0%

Non-Traditional Funds

4.0%

Bond Funds and Money Market Fund

71.0%

Bond Funds

71.0%

Money Market Fund

0.0%

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%.

MFS Lifetime 2025 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

29%

Bond Funds and Money Market Fund

71%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

29.4%

U.S. Equity Funds

20.3%

International Equity Funds

5.1%

Non-Traditional Funds

4.0%

Bond Funds and Money Market Fund

70.6%

Bond Funds

70.6%

Money Market Fund

0.0%

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.

MFS Lifetime 2030 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

41%

Bond Funds and Money Market Fund

59%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

40.7%

U.S. Equity Funds

28.4%

International Equity Funds

8.2%

Non-Traditional Funds

4.1%

Bond Funds and Money Market Fund

59.3%

Bond Funds

59.3%

Money Market Fund

0.0%

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.

MFS Lifetime 2035 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

61%

Bond Funds and Money Market Fund

39%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

60.7%

U.S. Equity Funds

41.4%

International Equity Funds

13.2%

Non-Traditional Funds

6.1%

Bond Funds and Money Market Fund

39.3%

Bond Funds

39.3%

Money Market Fund

0.0%

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.

MFS Lifetime 2040 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

80%

Bond Funds and Money Market Fund

20%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

80.3%

U.S. Equity Funds

52.1%

International Equity Funds

20.1%

Non-Traditional Funds

8.0%

Bond Funds and Money Market Fund

19.8%

Bond Funds

19.8%

Money Market Fund

0.0%

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.

MFS Lifetime 2045 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

88%

Bond Funds and Money Market Fund

12%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

87.8%

U.S. Equity Funds

54.6%

International Equity Funds

24.1%

Non-Traditional Funds

9.0%

Bond Funds and Money Market Fund

12.3%

Bond Funds

12.3%

Money Market Fund

0.0%

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.

MFS Lifetime 2050 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95%

Bond Funds and Money Market Fund

5%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95.0%

U.S. Equity Funds

57.0%

International Equity Funds

28.0%

Non-Traditional Funds

10.0%

Bond Funds and Money Market Fund

5.0%

Bond Funds

5.0%

Money Market Fund

0.0%

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.

MFS Lifetime 2055 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95%

Bond Funds and Money Market Fund

5%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95.0%

U.S. Equity Funds

57.0%

International Equity Funds

28.0%

Non-Traditional Funds

10.0%

Bond Funds and Money Market Fund

5.0%

Bond Funds

5.0%

Money Market Fund

0.0%

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.

MFS Lifetime 2060 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95%

Bond Funds and Money Market Fund

5%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95.0%

U.S. Equity Funds

57.0%

International Equity Funds

28.0%

Non-Traditional Funds

10.0%

Bond Funds and Money Market Fund

5.0%

Bond Funds

5.0%

Money Market Fund

0.0%

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.

MFS Lifetime 2065 Fund  
Prospectus [Line Items]  
Strategy [Heading] Principal Investment Strategies
Strategy Narrative [Text Block]

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, such as 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), 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, 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, 2025, the fund’s approximate long-term strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95%

Bond Funds and Money Market Fund

5%

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, 2025, the fund’s approximate strategic allocation among asset classes was:

  

Equity Funds and Non-Traditional Funds

95.0%

U.S. Equity Funds

57.0%

International Equity Funds

28.0%

Non-Traditional Funds

10.0%

Bond Funds and Money Market Fund

5.0%

Bond Funds

5.0%

Money Market Fund

0.0%

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.