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MFS® Total Return Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Supplement to Prospectus [Text Block] rr_SupplementToProspectusTextBlock
SUPPLEMENT TO THE PROSPECTUS

The date of this supplement is August 1, 2020.

MFS® Total Return Bond Fund
Risk/Return [Heading] rr_RiskReturnHeading MFS® Total Return Bond Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
Effective immediately, the sub-sections entitled "Fees and Expenses" and "Example" under the main heading "Summary of Key Information" are restated in their entirety as follows:

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy and hold shares of the fund, which are not reflected below. Expenses for Class 529B shares have been adjusted to reflect the full impact of the distribution fee.

You may qualify for sales charge reductions if, with respect to Class A or Class 529A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds, and, with respect to Class T shares, you invest at least $250,000 in the fund. 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 11 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Aug. 31, 2021
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This 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 and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
MFS® Total Return Bond Fund | A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.25%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.79%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.19%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.60%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if, with respect to Class A or Class 529A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds, and, with respect to Class T shares, you invest at least $250,000 in the fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 484
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 646
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 825
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,343
MFS® Total Return Bond Fund | T  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.50%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.79%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.70%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if, with respect to Class A or Class 529A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds, and, with respect to Class T shares, you invest at least $250,000 in the fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 250,000
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 320
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 486
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 668
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,194
MFS® Total Return Bond Fund | B  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 4.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.54%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.19%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.35%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 537
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 766
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,020
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,614
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 137
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 466
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 820
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,614
MFS® Total Return Bond Fund | C  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.54%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 248
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 477
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 830
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,826
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 148
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 477
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 830
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,826
MFS® Total Return Bond Fund | I  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.54%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 292
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 667
MFS® Total Return Bond Fund | R1  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.54%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 148
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 477
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 830
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,826
MFS® Total Return Bond Fund | R2  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.04%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 321
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 564
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,262
MFS® Total Return Bond Fund | R3  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.79%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.70%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 72
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 242
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 429
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 969
MFS® Total Return Bond Fund | R4  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.54%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 292
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 667
MFS® Total Return Bond Fund | R6  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.04%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.44%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.08%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 37
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 132
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 237
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 546
MFS® Total Return Bond Fund | 529A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.25%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.84%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.19%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.65%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if, with respect to Class A or Class 529A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds, and, with respect to Class T shares, you invest at least $250,000 in the fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 489
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 661
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 851
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,399
MFS® Total Return Bond Fund | 529B  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 4.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.59%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 553
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 792
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,056
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,679
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 153
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 492
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 856
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,679
MFS® Total Return Bond Fund | 529C  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.59%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 253
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 492
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 856
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,881
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 153
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 492
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 856
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,881
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
[2] Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.40% of the fund's average daily assets annually up to $2.5 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2021. MFS Fund Distributors, Inc., has agreed in writing to waive the Class A, Class 529A, and Class B service fee to 0.15% of each class' average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2021. Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.60% of the class' average daily net assets annually for Class A shares, 1.35% of the class' average daily net assets annually for Class B shares, 1.45% of the class' average daily net assets annually for each of Class C and Class R1 shares, 0.45% of the class' average daily net assets annually for each of Class I and Class R4 shares, 0.95% of the class' average daily net assets annually for Class R2 shares, 0.70% of the class' average daily net assets annually for each of Class R3 and Class T shares, 0.36% of the class' average daily net assets annually for Class R6 shares, 0.65% of the class' average daily net assets annually for Class 529A shares, and 1.50% of the class' average daily net assets annually for each of Class 529B and Class 529C shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2021.