MFS Institutional Money Market Portfolio Fund Information and Unaudited Holdings as of August 31, 2020 Weighted Average : 27 days Weighted Average Life: 27 days

Final Maturity Date Maturity Date Rate Issuer Category of Investment CUSIP Principal Amount (a) (b) (c) Value Apple, Inc. Non-Financial Company 03785DJ15 33,000,000 09/01/20 09/01/20 0.00000% 32,999,935.98 Apple, Inc. Non-Financial Company Commercial Paper 03785DK54 10,009,000 10/05/20 10/05/20 0.10000% 10,008,202.08

Australia & New Zealand Banking Group Ltd. Financial Company Commercial Paper 05253AJR2 200,000,000 09/25/20 09/25/20 0.10000% 199,985,694.00

Australia & New Zealand Banking Group Ltd. Financial Company Commercial Paper 05253AK17 41,586,000 10/01/20 10/01/20 0.10000% 41,582,060.97

Bank of Montreal Certificate of Deposit 06367BSU4 150,000,000 11/25/20 11/25/20 0.16000% 150,001,074.00 U.S. Treasury Repurchase Agreement, if BOFA Securities Repurchase Agreement collateralized only by U.S. Treasuries 8F5951D 87,057,000 09/01/20 09/01/20 0.07000% 87,057,000.00 (including Strips) and cash Canadian Imperial Bank of Commerce Financial Company Commercial Paper 13608AJ15 78,500,000 09/01/20 09/01/20 0.00000% 78,499,817.10 Canadian Imperial Bank of Commerce Financial Company Commercial Paper 13608AJR8 143,000,000 09/25/20 09/25/20 0.14000% 142,987,487.50 Canadian Imperial Bank of Commerce Financial Company Commercial Paper 13608AKD7 100,000,000 10/13/20 10/13/20 0.13000% 99,983,994.00

Exxon Mobil Corp. Non-Financial Company Commercial Paper 30229AJR1 19,000,000 09/25/20 09/25/20 0.26000% 18,998,984.07

Exxon Mobil Corp. Non-Financial Company Commercial Paper 30229AKN8 40,000,000 10/22/20 10/22/20 0.11000% 39,994,973.20

Exxon Mobil Corp. Non-Financial Company Commercial Paper 30229AKS7 50,000,000 10/26/20 10/26/20 0.11000% 49,993,078.00

Federal Home Loan Banks U.S. Government Agency Debt 313384E39 10,706,000 09/01/20 09/01/20 0.00000% 10,706,000.00 Federal Home Loan Banks U.S. Government Agency Debt 313384F53 270,054,000 09/11/20 09/11/20 0.07600% 270,048,750.15 Federal Home Loan Banks U.S. Government Agency Debt 313384G94 269,000 09/23/20 09/23/20 0.08600% 268,988.49 Federal Home Loan Banks U.S. Government Agency Debt 313384E62 129,810,000 09/04/20 09/04/20 0.07300% 129,809,243.21 Federal Home Loan Banks U.S. Government Agency Debt 313384F38 148,997,000 09/09/20 09/09/20 0.07200% 148,994,681.61 Federal Home Loan Banks U.S. Government Agency Debt 313384M97 132,729,000 11/02/20 11/02/20 0.08500% 132,706,141.41 Federal Home Loan Banks U.S. Government Agency Debt 313384N54 5,490,000 11/06/20 11/06/20 0.09400% 5,488,993.52 Federal National Mortage Association U.S. Government Agency Debt 313588G25 3,261,000 09/16/20 09/16/20 0.15000% 3,260,904.88

Intel Corp. Non-Financial Company Commercial Paper 45826CJ43 100,000,000 09/04/20 09/04/20 0.08000% 99,999,222.00

Intel Corp. Non-Financial Company Commercial Paper 45826CJG6 50,000,000 09/16/20 09/16/20 0.08000% 49,998,422.00

U.S. Treasury Repurchase Agreement, if J.P. Morgan Repurchase Agreement collateralized only by U.S. Treasuries 8F5948D 654,008,000 09/01/20 09/01/20 0.07000% 654,008,000.00 (including Strips) and cash

Johnson & Johnson Non-Financial Company Commercial Paper 47816FJQ5 25,000,000 09/24/20 09/24/20 0.09000% 24,998,733.25

Mizuho Bank Ltd. Financial Company Commercial Paper 60689FJU3 96,700,000 09/28/20 09/28/20 0.26500% 96,689,695.65 Mizuho Bank Ltd. Financial Company Commercial Paper 60689FJ17 167,500,000 09/01/20 09/01/20 0.00000% 167,499,567.85 Mizuho Bank Ltd. Financial Company Commercial Paper 60689FKK3 50,000,000 10/19/20 10/19/20 0.21500% 49,989,179.00 National Bank of Canada Financial Company Commercial Paper 63307LJQ5 24,000,000 09/24/20 09/24/20 0.12000% 23,998,368.00 National Bank of Canada Financial Company Commercial Paper 63307LJM4 196,735,000 09/21/20 09/21/20 0.13000% 196,723,752.66 National Bank of Canada Financial Company Commercial Paper 63307LJJ1 100,000,000 09/18/20 09/18/20 0.13000% 99,995,300.00

Novartis Finance Corp. Non-Financial Company Commercial Paper 6698M4JA1 42,000,000 09/10/20 09/10/20 0.09000% 41,997,666.48

Sumitomo Mitsui Banking Corp. Financial Company Commercial Paper 86562KJ88 24,000,000 09/08/20 09/08/20 0.12000% 23,999,466.72 Sumitomo Mitsui Banking Corp. Financial Company Commercial Paper 86562KJE5 119,300,000 09/14/20 09/14/20 0.24000% 119,295,220.84 Sumitomo Mitsui Banking Corp. Financial Company Commercial Paper 86562KKD5 170,500,000 10/13/20 10/13/20 0.21000% 170,476,783.02 Toronto-Dominion Bank Financial Company Commercial Paper 89119AKT4 50,000,000 10/27/20 10/27/20 0.12000% 49,989,075.00 Toronto-Dominion Bank Financial Company Commercial Paper 89119ALW6 47,500,000 11/30/20 11/30/20 0.16000% 47,480,789.10 Toronto-Dominion Bank Financial Company Commercial Paper 89119AM13 150,000,000 12/01/20 12/01/20 0.16000% 149,938,284.00 Toronto-Dominion Bank Financial Company Commercial Paper 89119AJU3 85,000,000 09/28/20 09/28/20 0.15400% 84,992,198.70

Toyota Motor Credit Corp. Non-Financial Company Commercial Paper 89233GPB6 50,000,000 02/11/21 02/11/21 0.31000% 49,938,728.00

United States Treasury Bill U.S. Treasury Debt 912796XH7 290,375,000 09/03/20 09/03/20 0.09100% 290,373,649.76 United States Treasury Bill U.S. Treasury Debt 9127964Q9 150,000,000 11/03/20 11/03/20 0.07700% 149,976,375.00 United States Treasury Bill U.S. Treasury Debt 912796TN9 41,580,000 10/08/20 10/08/20 0.12900% 41,576,153.85 United States Treasury Bill U.S. Treasury Debt 9127962J7 92,000,000 10/01/20 10/01/20 0.08500% 91,992,908.64 United States Treasury Bill U.S. Treasury Debt 9127962R9 200,000,000 10/15/20 10/15/20 0.08100% 199,977,084.00 United States Treasury Bill U.S. Treasury Debt 9127962S7 93,725,000 10/22/20 10/22/20 0.10700% 93,712,054.70 United States Treasury Bill U.S. Treasury Debt 9127962T5 33,555,000 10/29/20 10/29/20 0.10300% 33,549,864.07

United States Treasury Bill U.S. Treasury Debt 9127963R8 255,520,000 09/01/20 09/01/20 0.00000% 255,520,000.00

United States Treasury Bill U.S. Treasury Debt 9127963X5 744,780,000 09/08/20 09/08/20 0.08300% 744,768,053.73 United States Treasury Bill U.S. Treasury Debt 9127963Y3 405,630,000 09/15/20 09/15/20 0.10000% 405,616,589.87 United States Treasury Bill U.S. Treasury Debt 9127963Z0 360,930,000 09/22/20 09/22/20 0.09700% 360,911,578.13 United States Treasury Bill U.S. Treasury Debt 9127964A4 290,000,000 09/29/20 09/29/20 0.10000% 289,980,262.60 United States Treasury Bill U.S. Treasury Debt 9127964G1 200,000,000 10/06/20 10/06/20 0.08000% 199,982,500.00 United States Treasury Bill U.S. Treasury Debt 9127964H9 55,490,000 10/13/20 10/13/20 0.08500% 55,484,011.52 United States Treasury Bill U.S. Treasury Debt 9127964J5 255,520,000 10/20/20 10/20/20 0.08500% 255,486,958.71 United States Treasury Bill U.S. Treasury Debt 9127962G3 200,000,000 09/17/20 09/17/20 0.10900% 199,992,222.00 United States Treasury Bill U.S. Treasury Debt 9127964U0 205,620,000 12/01/20 12/01/20 0.10200% 205,570,622.41 United States Treasury Bill U.S. Treasury Debt 912796TJ8 370,000,000 09/10/20 09/10/20 0.09200% 369,992,600.00 United States Treasury Bill U.S. Treasury Debt 912796TP4 150,000,000 11/05/20 11/05/20 0.08600% 149,974,270.50

Page 1 of 2 United States Treasury Bill U.S. Treasury Debt 9127962H1 322,030,000 09/24/20 09/24/20 0.10100% 322,013,025.80 Total Value 8,571,835,241.73 (a) The maturity date as determined under rule 2a-7, taking into account the maturity shortening provisions of rule 2a-7(d).

(b) The final legal maturity date takes into account any maturity date extensions that may be effected at the option of the issuer or the effect of the securities' next demand feature date, if any.

(c) For commercial paper and other non-interest bearing securities generally traded on a discount basis, the coupon rate shown represents the market yield as of the date of this report. Other securities normally bear interest at the coupon rate shown.

Weighted Average Maturity (WAM) calculates an average time to maturity of all of the securities held in the portfolio, weighted by each 's percentage of the portfolio's amortized cost. The calculation takes into account any maturity shortening provisions such as demand features and interest rate resets.

Weighted Average Life (WAL) calculates an average time to maturity of all of the securities held in the portfolio, weighted by each security's percentage of the portfolio's amortized cost. The calculation takes into account consideration for both maturity date extensions or any maturity shortening provisions such as demand features on a security, but not interest rate resets.

The portfolio is actively managed and current holdings may be different.

You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The Fund may impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.

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