UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM N-CSR
CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES
Investment Company Act file number
811-02464
MFS SERIES TRUST IX
(Exact name of registrant as specified in charter)
111 Huntington Avenue, Boston, Massachusetts 02199
(Address of principal executive offices) (Zip code)
Christopher R. Bohane
Massachusetts Financial Services Company
111 Huntington Avenue
Boston, Massachusetts 02199
(Name and address of agents for service)
Registrant's telephone number, including area code:
(617) 954-5000
Date of fiscal year end:
October 31*
Date of reporting period:
April 30, 2026
*This Form N-CSR pertains to the following series of the Registrant: MFS Inflation-Adjusted Bond Fund. The remaining series of the Registrant have fiscal year ends of April 30.
ITEM 1.  REPORTS TO STOCKHOLDERS.
Item 1(a):
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class A-MIAAX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
A $33 0.66%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABA-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class B-MIABX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
B $70 1.40%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABB-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class C-MIACX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
C $75 1.51%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABC-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class I-MIAIX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
I $25 0.51%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABI-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class R1-MIALX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
R1 $75 1.51%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABR1-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class R2-MIATX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
R2 $50 1.01%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABR2-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class R3-MIAHX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
R3 $38 0.76%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABR3-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class R4-MIAJX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
R4 $25 0.51%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABR4-SEM
MFSLOGO_RED.EPS

MFS® Inflation-Adjusted
Bond Fund

TSR_Ribbon_red
Class R6-MIAKX
Semiannual Shareholder Report
This semiannual shareholder report contains important information about MFS Inflation-Adjusted Bond Fund for the period of November 1, 2025 to April 30, 2026. You can find additional information about the fund at funds.mfs.com. You can also request this information by contacting us at 1‑800‑225‑2606 or by sending an e-mail request to orderliterature@mfs.com.
FUND EXPENSES
What were the fund costs for the last six months?
(based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized)
R6 $20 0.41%
FUND STATISTICS AS OF 4/30/26
Net Assets ($): 1,511,260,673 Average Effective Maturity (yrs): 7.2
Total Number of Holdings: 108 Average Effective Duration (yrs): 6.9
Portfolio Turnover Rate (%): 10
Where the fund holds derivatives, they are not included in the total number of portfolio holdings.
PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 4/30/26)
Portfolio structure
Fixed Income 99.2%
Money Market Funds 0.8%
Composition including fixed income credit quality
AAA 2.3%
AA 1.2%
A 0.3%
U.S. Government 89.7%
Federal Agencies 5.7%
Money Market Funds 0.8%
Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change.
ADDITIONAL INFORMATION
You can find the fund’s summary prospectus, prospectus, most recent annual and semiannual reports, financial information, portfolio holdings, and statement of additional information online at funds.mfs.com. Proxy voting information is available without charge by calling 1‑800‑225‑2606, by visiting mfs.com/proxyvoting, or by visiting the SEC’s website at http://www.sec.gov.
IABR6-SEM

Item 1(b):

Not applicable.


ITEM 2.  CODE OF ETHICS.

During the period covered by this report, the Registrant has not amended any provision in its Code of Ethics (the “Code”) that relates to an element of the Code’s definition enumerated in paragraph (b) of Item 2 of this Form N-CSR. During the period covered by this report, the Registrant did not grant a waiver, including an implicit waiver, from any provision of the Code.


ITEM 3.  AUDIT COMMITTEE FINANCIAL EXPERT.

Not applicable for semi-annual reports.


ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

Not applicable for semi-annual reports.


ITEM 5.  AUDIT COMMITTEE OF LISTED REGISTRANTS.

Not applicable to the Registrant.


ITEM 6.  INVESTMENTS

A schedule of investments for each series covered by this Form N-CSR is included in the financial statements of such series under Item 7 of this Form N-CSR.


MFS Inflation-Adjusted Bond Fund
ITEM 7.  FINANCIAL STATEMENTS AND FINANCIAL HIGHLIGHTS FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.
MFS Inflation-Adjusted Bond Fund
Portfolio of Investments − 4/30/26 (unaudited)
The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.
 
Issuer
 
 
Shares/Par
Value ($)
Bonds – 99.3%
Asset-Backed & Securitized – 3.6%
3650R Commercial Mortgage Trust, 2021-PF1, “XA”, 1.101%, 11/15/2054 (i)
 
$
14,343,333
$467,363
AREIT 2022-CRE6 Trust, “AS”, FLR, 5.29% (SOFR - 30 day + 1.65%), 1/20/2037 (n)
 
 
2,462,500
2,459,190
ARI Fleet Lease Trust, 2025-A, “A2”, 4.38%, 1/17/2034 (n)
 
 
1,114,478
1,116,004
Babson CLO Ltd., 2021-3A, “B1R”, FLR, 5.305% (SOFR - 3mo. + 1.63%), 1/18/2035 (n)
 
 
3,000,000
3,001,209
BBCMS Mortgage Trust, 2021-C10, “XA”, 1.191%, 7/15/2054 (i)
 
 
11,883,301
542,073
BBCMS Mortgage Trust, 2021-C9, “XA”, 1.54%, 2/15/2054 (i)
 
 
7,621,000
440,675
Benchmark 2021-B23 Mortgage Trust, “XA”, 1.254%, 2/15/2054 (i)
 
 
25,011,737
1,056,411
Benchmark 2021-B24 Mortgage Trust, “XA”, 1.078%, 3/15/2054 (i)
 
 
14,431,651
529,903
Benchmark 2021-B27 Mortgage Trust, “XA”, 1.231%, 7/15/2054 (i)
 
 
20,297,235
883,602
Benchmark 2021-B28 Mortgage Trust, “XA”, 1.216%, 8/15/2054 (i)
 
 
24,083,018
1,111,335
Commercial Mortgage Pass-Through Certificates, 2021-BN31, “XA”, 1.279%, 2/15/2054 (i)
 
 
18,778,750
885,918
GreatAmerica Leasing Receivables Funding LLC, 2025-1, “A2”, 4.52%, 10/15/2027 (n)
 
 
1,810,971
1,814,839
JP Morgan Mortgage Trust, 2026-NQM1, “A1”, 4.745%, 6/25/2066 (n)
 
 
1,223,294
1,213,512
Morgan Stanley Capital I Trust, 2021-L5, “XA”, 1.178%, 5/15/2054 (i)
 
 
8,935,315
402,226
Morgan Stanley Capital I Trust, 2021-L6, “XA”, 1.141%, 6/15/2054 (i)
 
 
11,542,211
407,751
Morgan Stanley Capital I Trust, 2021-L7, “XA”, 1.054%, 10/15/2054 (i)
 
 
26,454,469
955,229
Morgan Stanley Residential Mortgage Loan Trust, 2025-NQM3, “A1”, 5.53%, 5/25/2070 (n)
 
 
1,207,735
1,212,829
New Residential Mortgage Loan Trust, 2026-NQM2, “A1”, 4.743%, 12/25/2065 (n)
 
 
3,803,752
3,768,979
OBX Trust, 2025-NQM8, “A1”, 5.472%, 3/25/2065 (n)
 
 
830,440
834,522
Palmer Square Loan Funding 2024-3A Ltd., “A2R”, FLR, 4.81% (SOFR - 3mo. + 1.15%), 8/08/2032 (n)
 
 
969,388
968,330
Palmer Square Loan Funding 2025-1A Ltd., “A2”, FLR, 4.853% (SOFR - 3mo. + 1.2%), 2/15/2033 (n)
 
 
4,300,000
4,299,914
Palmer Square Loan Funding 2025-2A Ltd., “A2”, FLR, 5.073% (SOFR - 3mo. + 1.4%), 7/15/2033 (n)
 
 
5,700,000
5,691,011
PFS Financing Corp., 2025-A, “A”, FLR, 4.289% (SOFR - 1mo. + 0.65%), 1/15/2029 (n)
 
 
3,476,000
3,479,693
PMT Loan Trust, 2025-INV10, “A36”, FLR, 4.995% (SOFR - 1mo. + 1.35%), 10/01/2056 (n)
 
 
1,515,317
1,522,017
PMT Loan Trust, 2026-CNF1, “A26”, FLR, 4.845% (SOFR - 1mo. + 1.2%), 1/25/2057 (n)
 
 
1,402,426
1,399,471
PMT Loan Trust, 2026-INV2, “A35”, FLR, 4.795% (SOFR - 1mo. + 1.15%), 1/25/2057 (n)
 
 
7,588,488
7,612,956
Santander Drive Auto Receivables Trust, 2025-1, “A3”, 4.74%, 1/16/2029 
 
 
836,077
837,491
Shackleton 2019-14A CLO Ltd., “BRR”, FLR, 5.225% (SOFR - 3mo. + 1.55%), 7/20/2034 (n)
 
 
3,996,016
3,997,015
Wells Fargo Commercial Mortgage Trust, 2021-C60, “XA”, 1.49%, 8/15/2054 (i)
 
 
9,162,585
514,663
 
 
 
$53,426,131
Consumer Services – 0.1%
Conservation Fund, 3.474%, 12/15/2029 
 
$
1,438,000
$1,372,169
Medical & Health Technology & Services – 0.2%
ProMedica Toledo Hospital, “B”, AGM, 5.325%, 11/15/2028 
 
$
2,421,000
$2,453,650
Mortgage-Backed – 5.7%
Fannie Mae, 2%, 9/25/2050 (i)
 
$
1,022,067
$135,076
Fannie Mae, 4%, 9/25/2050 (i)
 
 
2,003,522
385,140
Fannie Mae, 2.5%, 2/25/2051 (i)
 
 
1,367,697
190,667
Fannie Mae, 5.095%, 11/25/2053 
 
 
1,559,086
1,589,336
Fannie Mae, 5.645%, 11/25/2053 
 
 
3,592,505
3,701,962
Fannie Mae, 4.645%, 12/25/2054 
 
 
3,133,483
3,154,769
Fannie Mae, 5.045%, 12/25/2054 
 
 
1,012,006
1,024,585
Fannie Mae, 4.945%, 1/25/2055 
 
 
4,310,196
4,357,534
Freddie Mac, 0.601%, 5/25/2029 (i)
 
 
25,376,417
308,103
Freddie Mac, 1.004%, 7/25/2029 (i)
 
 
28,847,080
712,471
Freddie Mac, 0.733%, 1/25/2030 (i)
 
 
7,343,996
144,091
IABFS-SEM
1
MFS Inflation-Adjusted Bond Fund
Portfolio of Investments (unaudited) – continued
Issuer
 
 
Shares/Par
Value ($)
Bonds – continued
Mortgage-Backed – continued
Freddie Mac, 1.436%, 1/25/2030 (i)
 
$
13,335,214
$569,572
Freddie Mac, 1.913%, 4/25/2030 (i)
 
 
3,519,182
226,936
Freddie Mac, 1.769%, 5/25/2030 (i)
 
 
6,326,494
395,450
Freddie Mac, 1.47%, 6/25/2030 (i)
 
 
9,598,260
446,764
Freddie Mac, 1.261%, 9/25/2030 (i)
 
 
3,529,812
162,158
Freddie Mac, 0.802%, 12/25/2030 (i)
 
 
1,823,342
50,949
Freddie Mac, 0.408%, 1/25/2031 (i)
 
 
29,416,189
339,998
Freddie Mac, 0.627%, 1/25/2031 (i)
 
 
54,980,294
1,292,862
Freddie Mac, 0.87%, 1/25/2031 (i)
 
 
11,388,256
389,531
Freddie Mac, 1.026%, 1/25/2031 (i)
 
 
8,529,316
333,316
Freddie Mac, 0.604%, 3/25/2031 (i)
 
 
35,999,459
730,166
Freddie Mac, 1.322%, 5/25/2031 (i)
 
 
4,421,663
237,672
Freddie Mac, 1.039%, 7/25/2031 (i)
 
 
7,521,262
334,732
Freddie Mac, 0.632%, 9/25/2031 (i)
 
 
32,486,236
834,214
Freddie Mac, 0.954%, 9/25/2031 (i)
 
 
9,783,880
394,609
Freddie Mac, 0.441%, 11/25/2031 (i)
 
 
49,721,062
865,803
Freddie Mac, 0.595%, 12/25/2031 (i)
 
 
50,485,813
1,207,040
Freddie Mac, 0.664%, 12/25/2031 (i)
 
 
8,215,224
219,516
Freddie Mac, 0.431%, 5/25/2033 (i)
 
 
29,100,000
574,716
Freddie Mac, 1.092%, 9/25/2034 (i)
 
 
7,419,164
499,103
Freddie Mac, 0.427%, 1/25/2035 (i)
 
 
35,704,535
781,487
Freddie Mac, 2.5%, 11/25/2050 - 3/25/2051 (i)
 
 
4,914,608
801,932
Freddie Mac, 3%, 10/25/2052 (i)
 
 
902,229
145,373
Freddie Mac, 4.745%, 9/25/2054 
 
 
1,818,319
1,833,509
Freddie Mac, 4.595%, 2/25/2055 
 
 
3,526,485
3,552,061
Freddie Mac, 2.345%, 8/15/2057 (i)
 
 
1,100,362
138,532
Ginnie Mae, 4.94%, 10/20/2053 
 
 
7,354,841
7,434,776
Ginnie Mae, 4.99%, 10/20/2053 
 
 
7,184,658
7,270,001
Ginnie Mae, 4.74%, 11/20/2053 
 
 
6,067,804
6,123,018
Ginnie Mae, 4.84%, 12/20/2053 
 
 
7,182,999
7,247,714
Ginnie Mae, 4.59%, 3/20/2054 
 
 
6,673,276
6,701,213
Ginnie Mae, 4.69%, 10/20/2054 
 
 
1,572,623
1,580,898
Ginnie Mae, 7.59%, 5/20/2055 
 
 
1,067,437
1,093,118
Ginnie Mae, 6.114%, 6/20/2055 
 
 
2,590,552
2,624,543
Ginnie Mae, 6.189%, 6/20/2055 
 
 
1,447,251
1,401,790
Ginnie Mae, 4.64%, 12/20/2064 
 
 
1,806,878
1,816,235
Ginnie Mae, 4.44%, 8/20/2065 
 
 
2,955,683
2,960,025
Ginnie Mae, 4.54%, 1/20/2067 
 
 
1,001,023
1,007,983
Ginnie Mae, 4.09%, 5/20/2067 
 
 
3,118,896
3,116,475
Ginnie Mae, 4.158%, 8/20/2067 
 
 
1,934,809
1,931,247
Ginnie Mae, 4.29%, 8/20/2074 
 
 
1,166,779
1,169,403
 
 
 
$86,540,174
Municipals – 0.0%
Colorado Health Facilities Authority Rev., Taxable (Covenant Living Communities and Services), “B”, 2.8%, 12/01/2026 
 
$
380,000
$375,258
U.S. Treasury Inflation Protected Securities – 89.7%
U.S. Treasury Bonds, 3.625%, 4/15/2028 
 
$
68,611,782
$72,216,720
U.S. Treasury Bonds, 1.125%, 1/15/2033 
 
 
77,728,735
75,495,826
U.S. Treasury Bonds, 0.75%, 2/15/2042 
 
 
107,028,923
82,806,023
U.S. Treasury Bonds, 0.625%, 2/15/2043 
 
 
37,547,803
27,761,286
U.S. Treasury Bonds, 0.75%, 2/15/2045 
 
 
55,115,085
39,678,753
U.S. Treasury Bonds, 1%, 2/15/2048 
 
 
25,635,607
18,452,445
U.S. Treasury Bonds, 0.125%, 2/15/2052 
 
 
42,559,745
22,151,682
2
MFS Inflation-Adjusted Bond Fund
Portfolio of Investments (unaudited) – continued
Issuer
 
 
Shares/Par
Value ($)
Bonds – continued
U.S. Treasury Inflation Protected Securities – continued
U.S. Treasury Bonds, 2.125%, 2/15/2054 
 
$
41,183,561
$36,260,850
U.S. Treasury Notes, 0.5%, 1/15/2028 
 
 
26,729,367
26,594,529
U.S. Treasury Notes, 0.75%, 7/15/2028 
 
 
5,207,400
5,209,660
U.S. Treasury Notes, 0.875%, 1/15/2029 (f)
 
 
114,895,600
114,586,242
U.S. Treasury Notes, 0.125%, 1/15/2030 
 
 
12,373,606
11,916,819
U.S. Treasury Notes, 1.625%, 4/15/2030 
 
 
58,175,463
59,084,121
U.S. Treasury Notes, 0.125%, 7/15/2030 
 
 
150,219,642
144,029,793
U.S. Treasury Notes, 1.125%, 10/15/2030 
 
 
62,636,120
62,493,825
U.S. Treasury Notes, 0.125%, 1/15/2031 
 
 
181,171,924
171,672,318
U.S. Treasury Notes, 0.125%, 1/15/2032 (f)
 
 
105,722,948
98,201,907
U.S. Treasury Notes, 0.625%, 7/15/2032 
 
 
11,809,560
11,239,139
U.S. Treasury Notes, 1.375%, 7/15/2033 
 
 
70,585,364
69,561,980
U.S. Treasury Notes, 1.75%, 1/15/2034 
 
 
116,785,752
117,193,695
U.S. Treasury Notes, 1.875%, 7/15/2034 
 
 
40,668,232
41,160,471
U.S. Treasury Notes, 1.875%, 1/15/2036 
 
 
48,520,117
48,338,273
 
 
 
$1,356,106,357
Total Bonds (Identified Cost, $1,542,526,456)
$1,500,273,739
Mutual Funds (h) – 0.8%
Money Market Funds – 0.8%
MFS Institutional Money Market Portfolio, 3.7% (v) (Identified Cost, $11,862,698)
 
 
11,862,554
$11,863,740
Other Assets, Less Liabilities – (0.1)%
(876,806)
Net Assets – 100.0%
$1,511,260,673
 
(f)
All or a portion of the security has been segregated as collateral for open futures contracts and cleared swap agreements.
(h)
An affiliated issuer, which may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under
common control. At period end, the aggregate values of the fund's investments in affiliated issuers and in unaffiliated issuers were $11,863,740 and
$1,500,273,739, respectively.
(i)
Interest only security for which the fund receives interest on notional principal (Par amount). Par amount shown is the notional principal and does not
reflect the cost of the security.
(n)
Securities exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be sold in the ordinary course of business in
transactions exempt from registration, normally to qualified institutional buyers. At period end, the aggregate value of these securities was $44,391,491,
representing 2.9% of net assets.
(v)
Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the
annualized seven-day yield of the fund at period end.
 
The following abbreviations are used in this report and are defined:
AGM
Assured Guaranty Municipal
CLO
Collateralized Loan Obligation
CPI-U
Consumer Price Index - Urban Consumers
FLR
Floating Rate. Interest rate resets periodically based on the parenthetically disclosed reference rate plus a spread (if any). The period-end rate
reported may not be the current rate. All reference rates are USD unless otherwise noted.
SOFR
Secured Overnight Financing Rate
 
Derivative Contracts at 4/30/26
Futures Contracts
Description
Long/
Short
Currency
Contracts
Notional
Amount
Expiration
Date
Value/Unrealized
Appreciation
(Depreciation)
Asset Derivatives
Interest Rate Futures
U.S. Treasury Ultra Bond 30 yr
Short
USD
166
$19,095,188
June – 2026
$331,364
3
MFS Inflation-Adjusted Bond Fund
Portfolio of Investments (unaudited) – continued
Futures Contracts - continued
Description
Long/
Short
Currency
Contracts
Notional
Amount
Expiration
Date
Value/Unrealized
Appreciation
(Depreciation)
Liability Derivatives
Interest Rate Futures
U.S. Treasury Note 2 yr
Long
USD
1,815
$375,931,875
June – 2026
$(2,209,533
)
U.S. Treasury Note 5 yr
Long
USD
1,436
154,852,407
June – 2026
(1,062,250
)
 
$(3,271,783
)
 
Cleared Swap Agreements
Maturity
Date
Notional
Amount
Counterparty
Cash Flows
to Receive/
Frequency
Cash Flows
to Pay/
Frequency
Unrealized
Appreciation
(Depreciation)
Net
Unamortized
Upfront
Payments
(Receipts)
Value
Asset Derivatives
Interest Rate Swaps
4/30/29
USD
75,740,000
centrally cleared
1-day SOFR / Annually
3.637% / Annually
$118,088
$—
$118,088
1/14/31
USD
46,157,000
centrally cleared
1-day SOFR / Annually
3.511% / Annually
440,949
—
440,949
 
 
 
 
 
$559,037
$—
$559,037
Inflation Swaps
2/05/27
USD
80,400,000
centrally cleared
CPI-U / At Maturity
2.755% / At Maturity
$679,000
$—
$679,000
3/20/27
USD
76,800,000
centrally cleared
CPI-U / At Maturity
3.291% / At Maturity
233,916
—
233,916
10/14/28
USD
84,400,000
centrally cleared
CPI-U / At Maturity
2.740% / Annually
416,047
—
416,047
 
 
 
 
 
$1,328,963
$—
$1,328,963
 
 
 
 
 
$1,888,000
$—
$1,888,000
Liability Derivatives
Inflation Swaps
10/14/26
USD
84,400,000
centrally cleared
3.170% / At Maturity
CPI-U / Annually
$(549,626
)
$—
$(549,626
)
At April 30, 2026, the fund had liquid securities collateral with an aggregate value of $9,147,940 to cover any collateral or margin obligations for certain derivative contracts.
See Notes to Financial Statements
4
MFS Inflation-Adjusted Bond Fund
Financial Statements | Statement of Assets and Liabilities
This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund. 
At 4/30/26 (unaudited)
Assets
Investments in unaffiliated issuers, at value (identified cost, $1,542,526,456)
$1,500,273,739
Investments in affiliated issuers, at value (identified cost, $11,862,698)
11,863,740
Cash
510,811
Receivables for
Net daily variation margin on open futures contracts
558,772
Fund shares sold
155,042
Interest and dividends
3,710,933
Other assets
18,259
Total assets
$1,517,091,296
Liabilities
Payables for
Net daily variation margin on open cleared swap agreements
$226,406
Investments purchased
5,167,050
Fund shares reacquired
302,255
Payable to affiliates
Investment adviser
30,566
Administrative services fee
1,174
Shareholder servicing costs
25,179
Distribution and service fees
477
Payable for independent Trustees' compensation
5,368
Accrued expenses and other liabilities
72,148
Total liabilities
$5,830,623
Net assets
$1,511,260,673
Net assets consist of
Paid-in capital
$1,766,200,833
Total distributable earnings (loss)
(254,940,160
)
Net assets
$1,511,260,673
Shares of beneficial interest outstanding
165,070,800
 
 
Net assets
Shares
outstanding
Net asset value
per share (a)
Class A
$43,960,980
4,825,109
$9.11
Class B
42,047
4,642
9.06
Class C
1,244,575
138,067
9.01
Class I
27,764,822
3,042,985
9.12
Class R1
638,986
71,240
8.97
Class R2
159,174
17,527
9.08
Class R3
370,258
40,641
9.11
Class R4
109,669
12,032
9.12
Class R6
1,436,970,162
156,918,557
9.16
 
(a)
Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum
offering price per share was $9.51 [100 / 95.75 x $9.11]. On sales of $50,000 or more, the maximum offering price of Class A shares is
reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per
share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.
See Notes to Financial Statements
5
MFS Inflation-Adjusted Bond Fund
Financial Statements | Statement of Operations
This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations. 
Six months ended 4/30/26 (unaudited)
Net investment income (loss)
 
Income
Interest
$25,388,395
Dividends from affiliated issuers
332,586
Other
194
Total investment income
$25,721,175
Expenses
Management fee
$3,405,747
Distribution and service fees
69,890
Shareholder servicing costs
55,087
Administrative services fee
105,045
Independent Trustees' compensation
15,888
Custodian fee
44,655
Shareholder communications
9,370
Audit and tax fees
29,756
Legal fees
3,730
Miscellaneous
106,599
Total expenses
$3,845,767
Reduction of expenses by investment adviser and distributor
(621,955
)
Net expenses
$3,223,812
Net investment income (loss)
$22,497,363
Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers
$(7,665,574
)
Affiliated issuers
(8,021
)
Futures contracts
(1,379,088
)
Swap agreements
424,931
Net realized gain (loss)
$(8,627,752
)
Change in unrealized appreciation or depreciation
Unaffiliated issuers
$765,277
Affiliated issuers
(1,078
)
Futures contracts
(2,766,217
)
Swap agreements
377,120
Net unrealized gain (loss)
$(1,624,898
)
Net realized and unrealized gain (loss)
$(10,252,650
)
Change in net assets from operations
$12,244,713
See Notes to Financial Statements
6
MFS Inflation-Adjusted Bond Fund
Financial Statements | Statements of Changes in Net Assets
These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions. 
 
Six months ended
Year ended
 

4/30/26
(unaudited)

10/31/25
Change in net assets
 
 
From operations
Net investment income (loss)
$22,497,363
$61,946,604
Net realized gain (loss)
(8,627,752
)
(24,121,584
)
Net unrealized gain (loss)
(1,624,898
)
44,410,723
Change in net assets from operations
$12,244,713
$82,235,743
Total distributions to shareholders
$(22,601,609
)
$(66,769,862
)
Change in net assets from fund share transactions
$(40,333,773
)
$25,600,752
Total change in net assets
$(50,690,669
)
$41,066,633
Net assets
At beginning of period
1,561,951,342
1,520,884,709
At end of period
$1,511,260,673
$1,561,951,342
See Notes to Financial Statements
7
MFS Inflation-Adjusted Bond Fund
Financial Statements | Financial Highlights
The financial highlights table is intended to help you understand the fund's financial performance for the semiannual period and the past 5 fiscal years. Certain information reflects financial results for a single fund share. The total returns in the table represent the rate that an investor would have earned (or lost) on an investment in the fund share class (assuming reinvestment of all distributions) held for the entire period. 
Class A 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.17
$9.08
$8.67
$9.36
$11.46
$11.20
Income (loss) from investment operations
Net investment income (loss) (d)
$0.12
$0.35
$0.30
$0.34
$0.63
$0.40
Net realized and unrealized gain (loss)
(0.05
)
0.12
0.45
(0.58
)
(1.92
)
0.21
Total from investment operations
$0.07
$0.47
$0.75
$(0.24
)
$(1.29
)
$0.61
Less distributions declared to shareholders
From net investment income
$(0.13
)
$(0.38
)
$(0.34
)
$(0.45
)
$(0.81
)
$(0.35
)
Net asset value, end of period (x)
$9.11
$9.17
$9.08
$8.67
$9.36
$11.46
Total return (%) (r)(s)(t)(x)
0.73
(n)
5.34
8.71
(2.75
)
(11.79
)
5.48
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
0.84
(a)
0.83
0.82
0.82
0.81
0.87
Expenses after expense reductions
0.66
(a)
0.65
0.64
0.64
0.64
0.66
Net investment income (loss)
2.73
(a)
3.87
3.27
3.70
6.02
3.55
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$43,961
$47,565
$51,448
$75,213
$117,619
$114,091
 
Class B 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.13
$9.02
$8.60
$9.29
$11.37
$11.13
Income (loss) from investment operations
Net investment income (loss) (d)
$0.08
$0.26
$0.23
$0.26
$0.54
$0.28
Net realized and unrealized gain (loss)
(0.05
)
0.14
0.46
(0.57
)
(1.90
)
0.23
Total from investment operations
$0.03
$0.40
$0.69
$(0.31
)
$(1.36
)
$0.51
Less distributions declared to shareholders
From net investment income
$(0.10
)
$(0.29
)
$(0.27
)
$(0.38
)
$(0.72
)
$(0.27
)
Net asset value, end of period (x)
$9.06
$9.13
$9.02
$8.60
$9.29
$11.37
Total return (%) (r)(s)(t)(x)
0.36
(n)
4.55
8.02
(3.51
)
(12.47
)
4.62
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
1.58
(a)
1.58
1.57
1.57
1.56
1.62
Expenses after expense reductions
1.40
(a)
1.40
1.39
1.39
1.38
1.41
Net investment income (loss)
1.74
(a)
2.85
2.55
2.82
5.12
2.51
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$42
$38
$167
$271
$568
$1,085
 
See Notes to Financial Statements
8
MFS Inflation-Adjusted Bond Fund
Financial Highlights - continued
Class C 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.09
$9.00
$8.59
$9.28
$11.37
$11.13
Income (loss) from investment operations
Net investment income (loss) (d)
$0.07
$0.27
$0.22
$0.26
$0.54
$0.28
Net realized and unrealized gain (loss)
(0.05
)
0.12
0.45
(0.58
)
(1.91
)
0.22
Total from investment operations
$0.02
$0.39
$0.67
$(0.32
)
$(1.37
)
$0.50
Less distributions declared to shareholders
From net investment income
$(0.10
)
$(0.30
)
$(0.26
)
$(0.37
)
$(0.72
)
$(0.26
)
Net asset value, end of period (x)
$9.01
$9.09
$9.00
$8.59
$9.28
$11.37
Total return (%) (r)(s)(t)(x)
0.27
(n)
4.46
7.85
(3.60
)
(12.54
)
4.52
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
1.59
(a)
1.58
1.57
1.57
1.56
1.62
Expenses after expense reductions
1.51
(a)
1.50
1.49
1.49
1.49
1.51
Net investment income (loss)
1.68
(a)
2.99
2.51
2.80
5.19
2.50
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$1,245
$1,984
$2,485
$3,287
$5,412
$6,115
 
Class I 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.19
$9.09
$8.67
$9.37
$11.48
$11.22
Income (loss) from investment operations
Net investment income (loss) (d)
$0.13
$0.43
$0.29
$0.35
$0.68
$0.46
Net realized and unrealized gain (loss)
(0.07
)
0.07
0.49
(0.59
)
(1.97
)
0.16
(g)
Total from investment operations
$0.06
$0.50
$0.78
$(0.24
)
$(1.29
)
$0.62
Less distributions declared to shareholders
From net investment income
$(0.13
)
$(0.40
)
$(0.36
)
$(0.46
)
$(0.82
)
$(0.36
)
Net asset value, end of period (x)
$9.12
$9.19
$9.09
$8.67
$9.37
$11.48
Total return (%) (r)(s)(t)(x)
0.68
(n)
5.62
9.01
(2.75
)
(11.73
)
5.60
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
0.59
(a)
0.59
0.57
0.57
0.56
0.62
Expenses after expense reductions
0.51
(a)
0.50
0.49
0.49
0.49
0.51
Net investment income (loss)
2.90
(a)
4.73
3.25
3.80
6.48
4.03
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$27,765
$32,574
$8,428
$7,428
$22,796
$13,708
 
See Notes to Financial Statements
9
MFS Inflation-Adjusted Bond Fund
Financial Highlights - continued
Class R1 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.05
$8.97
$8.56
$9.25
$11.34
$11.10
Income (loss) from investment operations
Net investment income (loss) (d)
$0.08
$0.27
$0.22
$0.27
$0.53
$0.29
Net realized and unrealized gain (loss)
(0.06
)
0.12
0.45
(0.58
)
(1.90
)
0.21
Total from investment operations
$0.02
$0.39
$0.67
$(0.31
)
$(1.37
)
$0.50
Less distributions declared to shareholders
From net investment income
$(0.10
)
$(0.31
)
$(0.26
)
$(0.38
)
$(0.72
)
$(0.26
)
Net asset value, end of period (x)
$8.97
$9.05
$8.97
$8.56
$9.25
$11.34
Total return (%) (r)(s)(t)(x)
0.27
(n)
4.41
7.91
(3.56
)
(12.55
)
4.55
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
1.59
(a)
1.58
1.57
1.57
1.56
1.62
Expenses after expense reductions
1.51
(a)
1.50
1.49
1.49
1.49
1.51
Net investment income (loss)
1.90
(a)
3.04
2.43
2.91
5.08
2.56
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$639
$670
$615
$624
$874
$837
 
Class R2 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.15
$9.06
$8.65
$9.33
$11.43
$11.18
Income (loss) from investment operations
Net investment income (loss) (d)
$0.10
$0.32
$0.29
$0.31
$0.57
$0.35
Net realized and unrealized gain (loss)
(0.05
)
0.12
0.43
(0.58
)
(1.90
)
0.21
Total from investment operations
$0.05
$0.44
$0.72
$(0.27
)
$(1.33
)
$0.56
Less distributions declared to shareholders
From net investment income
$(0.12
)
$(0.35
)
$(0.31
)
$(0.41
)
$(0.77
)
$(0.31
)
Net asset value, end of period (x)
$9.08
$9.15
$9.06
$8.65
$9.33
$11.43
Total return (%) (r)(s)(t)(x)
0.52
(n)
4.97
8.38
(3.05
)
(12.15
)
5.07
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
1.08
(a)
1.08
1.07
1.07
1.06
1.12
Expenses after expense reductions
1.01
(a)
1.00
0.99
0.99
0.99
1.01
Net investment income (loss)
2.15
(a)
3.49
3.17
3.31
5.46
3.11
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$159
$264
$311
$251
$589
$686
 
See Notes to Financial Statements
10
MFS Inflation-Adjusted Bond Fund
Financial Highlights - continued
Class R3 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.17
$9.08
$8.66
$9.35
$11.45
$11.20
Income (loss) from investment operations
Net investment income (loss) (d)
$0.09
$0.35
$0.29
$0.30
$0.62
$0.37
Net realized and unrealized gain (loss)
(0.03
)
0.12
0.46
(0.55
)
(1.92
)
0.22
Total from investment operations
$0.06
$0.47
$0.75
$(0.25
)
$(1.30
)
$0.59
Less distributions declared to shareholders
From net investment income
$(0.12
)
$(0.38
)
$(0.33
)
$(0.44
)
$(0.80
)
$(0.34
)
Net asset value, end of period (x)
$9.11
$9.17
$9.08
$8.66
$9.35
$11.45
Total return (%) (r)(s)(t)(x)
0.71
(n)
5.25
8.72
(2.87
)
(11.90
)
5.30
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
0.83
(a)
0.83
0.82
0.82
0.81
0.87
Expenses after expense reductions
0.76
(a)
0.75
0.74
0.74
0.74
0.76
Net investment income (loss)
2.02
(a)
3.80
3.22
3.20
5.83
3.25
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$370
$880
$720
$850
$1,516
$2,128
 
Class R4 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.18
$9.09
$8.67
$9.36
$11.46
$11.20
Income (loss) from investment operations
Net investment income (loss) (d)
$0.13
$0.37
$0.32
$0.36
$0.63
$0.42
Net realized and unrealized gain (loss)
(0.06
)
0.12
0.46
(0.58
)
(1.91
)
0.20
Total from investment operations
$0.07
$0.49
$0.78
$(0.22
)
$(1.28
)
$0.62
Less distributions declared to shareholders
From net investment income
$(0.13
)
$(0.40
)
$(0.36
)
$(0.47
)
$(0.82
)
$(0.36
)
Net asset value, end of period (x)
$9.12
$9.18
$9.09
$8.67
$9.36
$11.46
Total return (%) (r)(s)(t)(x)
0.79
(n)
5.50
9.01
(2.59
)
(11.66
)
5.60
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
0.58
(a)
0.58
0.57
0.57
0.56
0.62
Expenses after expense reductions
0.51
(a)
0.50
0.49
0.49
0.48
0.51
Net investment income (loss)
2.91
(a)
4.03
3.49
3.94
6.00
3.68
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$110
$107
$93
$83
$84
$91
 
See Notes to Financial Statements
11
MFS Inflation-Adjusted Bond Fund
Financial Highlights - continued
Class R6 
Six months
ended
Year ended
 
4/30/26
(unaudited)
10/31/25
10/31/24
10/31/23
10/31/22
10/31/21
Net asset value, beginning of period
$9.22
$9.13
$8.71
$9.40
$11.51
$11.24
Income (loss) from investment operations
Net investment income (loss) (d)
$0.13
$0.37
$0.33
$0.37
$0.64
$0.42
Net realized and unrealized gain (loss)
(0.05
)
0.13
0.45
(0.59
)
(1.92
)
0.22
Total from investment operations
$0.08
$0.50
$0.78
$(0.22
)
$(1.28
)
$0.64
Less distributions declared to shareholders
From net investment income
$(0.14
)
$(0.41
)
$(0.36
)
$(0.47
)
$(0.83
)
$(0.37
)
Net asset value, end of period (x)
$9.16
$9.22
$9.13
$8.71
$9.40
$11.51
Total return (%) (r)(s)(t)(x)
0.84
(n)
5.56
9.05
(2.50
)
(11.62
)
5.74
Ratios (%) (to average net assets)
and Supplemental data:
Expenses before expense reductions
0.49
(a)
0.49
0.49
0.49
0.48
0.55
Expenses after expense reductions
0.41
(a)
0.41
0.41
0.41
0.41
0.44
Net investment income (loss)
2.97
(a)
4.09
3.59
4.01
6.07
3.71
Portfolio turnover rate
10
(n)
38
27
43
86
57
Net assets at end of period (000 omitted)
$1,436,970
$1,477,869
$1,456,617
$1,332,846
$1,355,560
$1,622,398
 
(a)
Annualized.
(d)
Per share data is based on average shares outstanding.
(g)
The per share amount varies from the net investment income and/or net realized and unrealized gain/loss for the period because of the timing of sales
of fund shares and the per share amounts of realized and unrealized gains and losses and/or inflation/deflation adjustments at such time.
(n)
Not annualized.
(r)
Certain expenses have been reduced without which performance would have been lower.
(s)
From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.
(t)
Total returns do not include any applicable sales charges.
(x)
The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted
accounting principles required at period end for financial reporting purposes.
See Notes to Financial Statements
12
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited)
(1) Business and Organization
MFS Inflation-Adjusted Bond Fund (the fund) is a diversified series of MFS Series Trust IX (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as an open-end management investment company.
The fund is an investment company and accordingly follows the investment company accounting and reporting guidance of the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946 Financial Services - Investment Companies.
(2) Significant Accounting Policies
General — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued.
Segment Reporting — An operating segment is defined in FASB Accounting Standards Codification Topic 280, Segment Reporting as a component of a public entity that engages in business activities from which it may recognize revenues and incur expenses, has operating results that are regularly reviewed by the entity’s chief operating decision maker (CODM) in making resource allocation decisions and assessing segment performance, and for which discrete financial information is available. The fund represents a single operating segment and the Chairman’s Committee of the fund's adviser acts as the segment’s CODM. The fund’s total returns, expense ratios, and changes in net assets which are used by the CODM to assess segment performance and to make resource allocation decisions to the segment are consistent with that presented within the fund’s financial statements.
Balance Sheet Offsetting — The fund's accounting policy with respect to balance sheet offsetting is that, absent an event of default by the counterparty or a termination of the agreement, the International Swaps and Derivatives Association (ISDA) Master Agreement, or similar agreement, does not result in an offset of reported amounts of financial assets and financial liabilities in the Statement of Assets and Liabilities across transactions between the fund and the applicable counterparty. The fund's right to setoff may be restricted or prohibited by the bankruptcy or insolvency laws of the particular jurisdiction to which a specific master netting agreement counterparty is subject. Balance sheet offsetting disclosures, to the extent applicable to the fund, have been included in the fund’s Significant Accounting Policies note under the captions for each of the fund’s in-scope financial instruments and transactions.
Investment Valuations — Subject to its oversight, the fund's Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund’s investments to MFS as the fund's adviser, pursuant to the fund’s valuation policy and procedures which have been adopted by the adviser and approved by the Board. In accordance with Rule 2a-5 under the Investment Company Act of 1940, the Board of Trustees designated the adviser as the “valuation designee” of the fund. If the adviser, as valuation designee, determines that reliable market quotations are not readily available for an investment, the investment is valued at fair value as determined in good faith by the adviser in accordance with the adviser’s fair valuation policy and procedures.
Under the fund's valuation policy and procedures, debt instruments and floating rate loans, including restricted debt instruments, are generally valued at an evaluated or composite bid as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value. Futures contracts are generally valued at last posted settlement price on their primary exchange as provided by a third-party pricing service. Futures contracts for which there were no trades that day for a particular position are generally valued at the closing bid quotation on their primary exchange as provided by a third-party pricing service. Swap agreements are generally valued using valuations provided by a third-party pricing service, which for cleared swaps includes an evaluation of any trading activity at the clearinghouses. Open-end investment companies are generally valued at net asset value per share.
Under the fund’s valuation policy and procedures, market quotations are not considered to be readily available for debt instruments, floating rate loans, and many types of derivatives. These investments are generally valued at fair value based on information from third-party pricing services or otherwise determined by the adviser in accordance with the adviser’s fair valuation policy and procedures. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, spreads and other market data. Pricing services generally value debt instruments assuming orderly transactions of institutional round lot sizes, but a fund may hold or transact in such securities in smaller, odd lot sizes. In instances where a fund holds an odd lot size position in a debt instrument, such
13
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
position will typically be valued using the pricing agent’s institutional round lot price for the debt instrument. Odd lots may trade at lower prices than institutional round lots, and the fund may receive different prices when it sells odd lot positions than it would receive for sales of institutional round lot positions. An investment may also be valued at fair value if the adviser determines that the investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as foreign exchange or market) and prior to the determination of the fund’s net asset value, or after the halt of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. The adviser generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment. The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.
Various inputs are used in determining the value of the fund's assets or liabilities. These inputs are categorized into three broad levels. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, an investment's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The fund's assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Level 1 includes unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes significant unobservable inputs, which may include the adviser's own assumptions in determining the fair value of investments. Other financial instruments are derivative instruments, such as futures contracts and swap agreements. The following is a summary of the levels used as of April 30, 2026 in valuing the fund's assets and liabilities:
 
Financial Instruments
Level 1
Level 2
Level 3
Total
U.S. Treasury Bonds & U.S. Government
Agencies & Equivalents
$—
$1,356,106,357
$—
$1,356,106,357
Municipal Bonds
—
375,258
—
375,258
U.S. Corporate Bonds
—
3,825,819
—
3,825,819
Residential Mortgage-Backed Securities
—
104,104,460
—
104,104,460
Commercial Mortgage-Backed Securities
—
10,656,339
—
10,656,339
Asset-Backed Securities (including CDOs)
—
25,205,506
—
25,205,506
Investment Companies
11,863,740
—
—
11,863,740
Total
$11,863,740
$1,500,273,739
$—
$1,512,137,479
 
Other Financial Instruments
 
 
 
 
Futures Contracts – Assets
$331,364
$—
$—
$331,364
Futures Contracts – Liabilities
(3,271,783
)
—
—
(3,271,783
)
Swap Agreements – Assets
—
1,888,000
—
1,888,000
Swap Agreements – Liabilities
—
(549,626
)
—
(549,626
)
For further information regarding security characteristics, see the Portfolio of Investments.
Inflation-Adjusted Debt Securities — The fund invests in inflation-adjusted debt securities issued by the U.S. Treasury.  The principal value of these debt securities is adjusted through income according to changes in the Consumer Price Index.  These debt securities typically pay a fixed rate of interest, but this fixed rate is applied to the inflation-adjusted principal amount.  The principal paid at maturity of the debt security is typically equal to the inflation-adjusted principal amount, or the security’s original par value, whichever is greater.  Other types of inflation-adjusted securities may use other methods to adjust for other measures of inflation.
Derivatives — The fund uses derivatives primarily to increase or decrease exposure to a particular market or segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives are used for hedging or non-hedging purposes. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. When the fund uses derivatives as an investment to increase market exposure, or for hedging purposes, gains and losses from derivative instruments may be substantially greater than the derivative’s original cost.
The derivative instruments used by the fund during the period were futures contracts and swap agreements. Depending on the type of derivative, a fund may exit a derivative position by entering into an offsetting transaction with a counterparty or exchange, negotiating an agreement with the derivative counterparty, or novating the position to a third party. The fund may be unable to
14
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
promptly close out a futures position in instances where the daily fluctuation in the price for that type of future exceeds the daily limit set by the exchange. The fund's period end derivatives, as presented in the Portfolio of Investments and the associated Derivative Contract tables, generally are indicative of the volume of its derivative activity during the period.
The following table presents, by major type of derivative contract, the fair value, on a gross basis, of the asset and liability components of derivatives held by the fund at April 30, 2026 as reported in the Statement of Assets and Liabilities: 
 
 
Fair Value (a)
Risk
Derivative Contracts
Asset Derivatives
Liability Derivatives
Interest Rate
Futures Contracts
$331,364
$(3,271,783)
Interest Rate
Cleared Swap Agreements
1,888,000
(549,626)
Total
 
$2,219,364
$(3,821,409)
(a) Values presented in this table for futures contracts and cleared swap agreements correspond to the values reported in the Portfolio of Investments. Only the current day net variation margin for futures contracts and cleared swap agreements is reported separately within the Statement of Assets and Liabilities.
The following table presents, by major type of derivative contract, the realized gain (loss) on derivatives held by the fund for the six months ended April 30, 2026 as reported in the Statement of Operations: 
Risk
Futures
Contracts
Swap
Agreements
Interest Rate
$(1,379,088
)
$424,931
The following table presents, by major type of derivative contract, the change in unrealized appreciation or depreciation on derivatives held by the fund for the six months ended April 30, 2026 as reported in the Statement of Operations: 
Risk
Futures
Contracts
Swap
Agreements
Interest Rate
$(2,766,217
)
$377,120
Derivative counterparty credit risk is managed through formal evaluation of the creditworthiness of all potential counterparties. On certain, but not all, uncleared derivatives, the fund attempts to reduce its exposure to counterparty credit risk whenever possible by entering into an ISDA Master Agreement on a bilateral basis. The ISDA Master Agreement gives each party to the agreement the right to terminate all transactions traded under such agreement if there is a specified deterioration in the credit quality of the other party. Upon an event of default or a termination of the ISDA Master Agreement, the non-defaulting party has the right to close out all transactions traded under such agreement and to net amounts owed under each agreement to one net amount payable by one party to the other. This right to close out and net payments across all transactions traded under the ISDA Master Agreement could result in a reduction of the fund's credit risk to such counterparty equal to any amounts payable by the fund under the applicable transactions, if any.
Collateral and margin requirements differ by type of derivative. For exchange-traded and cleared derivatives (e.g., futures contracts, cleared swaps, and exchange-traded options), margin requirements are set by the exchange or clearing broker and the clearing house and collateral, in the form of cash or securities, is posted by the fund directly with the exchange or clearing broker. Collateral terms are counterparty agreement specific for uncleared derivatives (e.g., forward foreign currency exchange contracts, uncleared swap agreements, and uncleared options). Collateral, in the form of cash and securities, is held in segregated accounts with the fund's custodian in connection with these agreements. For derivatives traded under an ISDA Master Agreement, which contains a credit support annex, the collateral requirements are netted across all transactions traded under such counterparty-specific agreement and an amount is posted from one party to the other to collateralize such obligations. Cash that has been segregated or delivered to brokers to cover the fund's collateral or margin obligations under derivative contracts, if any, will be reported separately in the Statement of Assets and Liabilities as cash collateral posted for uncleared derivatives and/or cash pledged for exchange-traded or cleared derivatives. Securities pledged as collateral or margin for the same purpose, if any, are noted in the Portfolio of Investments. The fund may be required to make payments of interest on uncovered collateral or margin obligations with the broker. Any such payments are included in “Miscellaneous” expense in the Statement of Operations.
Futures Contracts — The fund entered into futures contracts which may be used to hedge against or obtain broad market exposure, interest rate exposure, currency exposure, or to manage duration. A futures contract represents a commitment for the future purchase or sale of an asset at a specified price on a specified date.
15
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
Upon entering into a futures contract, the fund is required to deposit with the broker, either in cash or securities, an initial margin in an amount equal to a specified percentage of the notional amount of the contract. Subsequent payments (variation margin) are made or received by the fund each day, depending on the daily fluctuations in the value of the contract, and are recorded for financial statement purposes as unrealized gain or loss by the fund until the contract is closed or expires at which point the gain or loss on futures contracts is realized.
The fund bears the risk of interest rates, exchange rates or securities prices moving unexpectedly, in which case, the fund may not achieve the anticipated benefits of the futures contracts and may realize a loss. While futures contracts may present less counterparty risk to the fund since the contracts are exchange traded and the exchange’s clearinghouse guarantees payments to the broker, there is still counterparty credit risk due to the insolvency of the broker. The fund’s maximum risk of loss due to counterparty credit risk is equal to the margin posted by the fund to the broker plus any gains or minus any losses on the outstanding futures contracts.
Swap Agreements — The fund entered into swap agreements which generally involve a periodic exchange of cash payments on a net basis, at specified intervals or upon the occurrence of specified events, between the fund and a counterparty. Certain swap agreements may be entered into as a bilateral contract (“uncleared swaps”) while others are required to be centrally cleared (“cleared swaps”). 
Both cleared and uncleared swap agreements are marked to market daily.  The value of uncleared swap agreements is reported in the Statement of Assets and Liabilities as “Uncleared swaps, at value” which includes any related interest accruals to be paid or received by the fund.  For cleared swaps, payments (variation margin) are made or received by the fund each day, depending on the daily fluctuations in the value of the cleared swap, such that only the current day net receivable or payable for variation margin is reported in the Statement of Assets and Liabilities.
For both cleared and uncleared swaps, premiums paid or received at the inception of the agreements are amortized over the term of the agreement as realized gain or loss on swap agreements in the Statement of Operations. The periodic exchange of net cash payments, as well as any liquidation payment received or made upon early termination, are recorded as a realized gain or loss on swap agreements in the Statement of Operations. The change in unrealized appreciation or depreciation on swap agreements in the Statement of Operations reflects the aggregate change over the reporting period in the value of swaps net of any unamortized premiums paid or received.
Risks related to swap agreements include the possible lack of a liquid market, unfavorable market and interest rate movements of the underlying instrument and the failure of the counterparty to perform under the terms of the agreements. The fund's maximum risk of loss from counterparty credit risk is the discounted net value of the cash flows to be received from/paid to the counterparty over the contract's remaining life, to the extent that the amount is positive. To address counterparty risk, uncleared swap agreements are limited to only highly-rated counterparties.  Risk is further reduced by having an ISDA Master Agreement (“ISDA”) between the fund and the counterparty and, where applicable, by the posting of collateral by the counterparty to the fund to cover the fund’s exposure to the counterparty under such ISDA. The fund's counterparty risk due to cleared swaps is mitigated by the fact that the clearinghouse is the counterparty to the transaction and the regulatory requirement safeguards in the event of a clearing broker bankruptcy.
The fund entered into interest rate swap agreements in order to manage its exposure to interest rate fluctuations.  Interest rate swap agreements involve the periodic exchange of cash flows, between the fund and a counterparty, based on the difference between two interest rates applied to a notional principal amount. The two interest rates exchanged may either be a fixed rate and a floating rate or two floating rates based on different indices.
The fund entered into inflation swap agreements in order to manage its exposure to inflation risk.  Inflation swap agreements involve the periodic exchange of cash flows, between the fund and a counterparty, based on the difference between two rates applied to a notional principal amount. The two rates exchanged are generally a fixed rate and a floating rate based on an inflation index.
Indemnifications — Under the fund's organizational documents, its officers and Trustees may be indemnified against certain liabilities and expenses arising out of the performance of their duties to the fund. Additionally, in the normal course of business, the fund enters into agreements with service providers that may contain indemnification clauses. The fund's maximum exposure under these agreements is unknown as this would involve future claims that may be made against the fund that have not yet occurred.
Investment Transactions and Income —  Interest income is recorded on the accrual basis. All premium and discount is amortized or accreted for financial statement purposes in accordance with U.S. generally accepted accounting principles. Interest payments received in additional securities are recorded on the ex-interest date in an amount equal to the value of the security on such date. Inflation-indexed bonds are fixed-income securities whose principal value is periodically adjusted upward or downward based on the rate of inflation. Interest is accrued based on the principal amount, which is adjusted for inflation. Any increase or decrease in the principal amount of an inflation-indexed bond is generally recorded as an increase or decrease in interest income, respectively, even though the adjusted principal is not received until maturity.
16
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
The fund may receive proceeds from litigation settlements. Any proceeds received from litigation involving portfolio holdings are reflected in the Statement of Operations in realized gain/loss if the security has been disposed of by the fund or in unrealized gain/loss if the security is still held by the fund. Any other proceeds from litigation not related to portfolio holdings are reflected as other income in the Statement of Operations.
Investment transactions are recorded on the trade date.  In determining the net gain or loss on securities sold, the cost of securities is determined on the identified cost basis.
To mitigate the counterparty credit risk on To Be Announced (“TBA”) transactions, mortgage dollar rolls, and other types of forward settling mortgage-backed and asset-backed security transactions, the fund whenever possible enters into a Master Securities Forward Transaction Agreement (“MSFTA”) on a bilateral basis with each of the counterparties with whom it undertakes a significant volume of transactions.  The MSFTA gives each party to the agreement the right to terminate all transactions traded under such agreement if there is a specified deterioration in the credit quality of the other party.  Upon an event of default or a termination of the MSFTA, the non-defaulting party has the right to close out all transactions traded under such agreement and to net amounts owed under each transaction to one net amount payable by one party to the other.  This right to close out and net payments across all transactions traded under the MSFTA could result in a reduction of the fund's credit risk to such counterparty equal to any amounts payable by the fund under the applicable transactions, if any.
For mortgage-backed and asset-backed securities traded under a MSFTA, the collateral and margining requirements are contract specific. Collateral amounts across all transactions traded under such agreement are netted and an amount is posted from one party to the other to collateralize such obligations. Cash posted to cover the fund's collateral or margin obligations under a MSFTA, if any, will be reported separately on the Statement of Assets and Liabilities as cash collateral posted. Securities pledged as collateral or margin for the same purpose, if any, are noted in the Portfolio of Investments.
Tax Matters and Distributions — The fund intends to qualify as a regulated investment company, as defined under Subchapter M of the Internal Revenue Code, and to distribute all of its taxable income, including realized capital gains. As a result, no provision for federal income tax is required. The fund’s federal tax returns, when filed, will remain subject to examination by the Internal Revenue Service for generally a three year period. Management has analyzed the fund’s tax positions taken on federal and state tax returns for all open tax years and does not believe that there are any uncertain tax positions that require recognition of a tax liability. Foreign taxes, if any, have been accrued by the fund in the accompanying financial statements in accordance with the applicable foreign tax law. Foreign income taxes may be withheld by certain countries in which the fund invests. Additionally, capital gains realized by the fund on securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.
Distributions to shareholders are recorded on the ex-dividend date. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from U.S. generally accepted accounting principles. Certain capital accounts in the financial statements are periodically adjusted for permanent differences in order to reflect their tax character. These adjustments have no impact on net assets or net asset value per share. Temporary differences which arise from recognizing certain items of income, expense, gain or loss in different periods for financial statement and tax purposes will reverse at some time in the future.
Book/tax differences primarily relate to amortization of premium and accretion of discount of debt securities and wash sale loss deferrals.
The tax character of distributions made during the six months ended April 30, 2026 will be determined at fiscal year end. The tax character of distributions declared to shareholders for the last fiscal year is as follows: 
 
Year ended
10/31/25
Ordinary income (including any short-term capital gains)
$66,769,862
The federal tax cost and the tax basis components of distributable earnings were as follows: 
17
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
As of 4/30/26
Cost of investments
$1,570,984,948
Gross appreciation
14,671,761
Gross depreciation
(73,519,230
)
Net unrealized appreciation (depreciation)
$(58,847,469
)
As of 10/31/25
Undistributed ordinary income
8,886,556
Capital loss carryforwards
(192,301,599
)
Net unrealized appreciation (depreciation)
(61,168,221
)
The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.
As of October 31, 2025, the fund had capital loss carryforwards available to offset future realized gains. These net capital losses may be carried forward indefinitely and their character is retained as short-term and/or long-term losses. Such losses are characterized as follows: 
Short-Term
$(57,127,314
)
Long-Term
(135,174,285
)
Total
$(192,301,599
)
Multiple Classes of Shares of Beneficial Interest — The fund offers multiple classes of shares, which differ in their respective distribution and service fees. The fund's income, realized and unrealized gain (loss), and common expenses are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B and Class C shares will convert to Class A shares approximately eight years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows: 
 
Six months ended
4/30/26
Year ended
10/31/25
Class A
$642,095
$2,044,154
Class B
344
2,479
Class C
22,537
69,908
Class I
406,546
946,491
Class R1
7,720
21,944
Class R2
3,237
10,634
Class R3
11,903
33,152
Class R4
1,531
4,284
Class R6
21,505,696
63,636,816
Total
$22,601,609
$66,769,862
(3) Transactions with Affiliates
Investment Adviser — The fund has an investment advisory agreement with MFS to provide overall investment management and related administrative services and facilities to the fund. The management fee is computed daily and paid monthly at the following annual rates based on the fund's average daily net assets: 
Up to $1 billion
0.50%
In excess of $1 billion and up to $2.5 billion
0.35%
In excess of $2.5 billion and up to $5 billion
0.30%
In excess of $5 billion
0.29%
The investment adviser has agreed in writing to reduce its management fee to 0.40% of the fund’s average daily net assets annually up to $1 billion. This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue at least until February 28, 2027. For the six months ended April 30, 2026, this management fee reduction amounted to $495,891, which is included in the reduction of total expenses in the Statement of Operations. MFS has also agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. MFS has also agreed in writing to waive at least 0.01% of its management fee as part of this agreement. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but
18
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
such agreement will continue at least until February 28, 2027. For the six months ended April 30, 2026, this management fee reduction amounted to $103,567, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended April 30, 2026 was equivalent to an annual effective rate of 0.37% of the fund's average daily net assets.
The investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses, such that total fund operating expenses do not exceed the following rates annually of each class’s average daily net assets: 
Classes
A
B
C
I
R1
R2
R3
R4
R6
0.67%
1.42%
1.52%
0.52%
1.52%
1.02%
0.77%
0.52%
0.44%
This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue at least until February 28, 2027. For the six months ended April 30, 2026, the fund’s actual operating expenses did not exceed the limit and therefore, the investment adviser did not pay any portion of the fund’s expenses related to this agreement.
Distributor — MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $192 for the six months ended April 30, 2026, as its portion of the initial sales charge on sales of Class A shares of the fund.
The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule 12b-1 of the Investment Company Act of 1940.
The fund's distribution plan provides that the fund will pay MFD for services provided by MFD and financial intermediaries in connection with the distribution and servicing of certain share classes. One component of the plan is a distribution fee paid to MFD and another component of the plan is a service fee paid to MFD. MFD may subsequently pay all, or a portion, of the distribution and/or service fees to financial intermediaries. The distribution and service fees are computed daily and paid monthly.
Distribution Plan Fee Table: 
 
Distribution
Fee Rate (d)
Service
Fee Rate (d)
Total
Distribution
Plan (d)
Annual
Effective
Rate (e)
Distribution
and Service
Fee
Class A
—
0.25%
0.25%
0.15%
$56,184
Class B
0.75%
0.25%
1.00%
0.90%
218
Class C
0.75%
0.25%
1.00%
1.00%
8,857
Class R1
0.75%
0.25%
1.00%
1.00%
3,223
Class R2
0.25%
0.25%
0.50%
0.50%
542
Class R3
—
0.25%
0.25%
0.25%
866
Total Distribution and Service Fees
$69,890
(d)
 In accordance with the distribution plan for certain classes, the fund pays distribution and/or service fees equal to these annual percentage rates of each
class’s average daily net assets. The distribution and service fee rates disclosed by class represent the current rates in effect at the end of the reporting
period. Any rate changes, if applicable, are detailed below.
(e)
 The annual effective rates represent actual fees incurred under the distribution plan for the six months ended April 30, 2026 based on each class's average daily net assets.  0.10% of the Class A and Class B service fee is currently being waived under a written waiver arrangement. For the six months ended April 30, 2026, this waiver amounted to $22,473 and $22 for Class A and Class B shares, respectively, and is included in the reduction of total expenses in the Statement of Operations. These written waiver agreements will continue until modified by the fund’s Board of Trustees, but such agreements will continue at least until February 28, 2027. MFD has voluntarily agreed to rebate a portion of each class’s 0.25% service fee attributable to accounts for which there is no financial intermediary specified on the account except for accounts attributable to MFS or its affiliates’ seed money. For the six months ended April 30, 2026, this rebate amounted to $2 for Class A shares and is included in the reduction of total expenses in the Statement of Operations.
Certain Class A shares are subject to a contingent deferred sales charge (CDSC) in the event of a shareholder redemption within 18 months of purchase. Class B shares are subject to a CDSC in the event of a shareholder redemption within six years of purchase. Class C shares are subject to a CDSC in the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the six months ended April 30, 2026, were as follows: 
 
Amount
Class A
$135
Class B
—
Class C
13
19
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
Shareholder Servicing Agent — MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund's Board of Trustees. For the six months ended April 30, 2026, the fee was $13,093, which equated to 0.0017% annually of the fund's average daily net assets. MFSC also receives reimbursement from the fund for out-of-pocket expenses, sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incur sub-accounting fees. For the six months ended April 30, 2026, these out-of-pocket expenses, sub-accounting and other shareholder servicing costs amounted to $41,994.
Administrator — MFS provides certain financial, legal, shareholder communications, compliance, and other administrative services to the fund. Under an administrative services agreement, the fund reimburses MFS the costs incurred to provide these services. The fund is charged an annual fixed amount of $17,500 plus a fee based on average daily net assets. The administrative services fee is computed daily and paid monthly. The administrative services fee incurred for the six months ended April 30, 2026 was equivalent to an annual effective rate of 0.0138% of the fund's average daily net assets.
Trustees’ and Officers’ Compensation — The fund pays compensation to independent Trustees in the form of a retainer, attendance fees, and additional compensation to Board and Committee chairpersons. Independent Trustees’ compensation is accrued daily and paid subsequent to each Trustee Board meeting. The fund does not pay compensation directly to Trustees or officers of the fund who are also officers of the investment adviser, all of whom receive remuneration from MFS for their services to the fund. Certain officers and Trustees of the fund are officers or directors of MFS, MFD, and MFSC.
Other — The fund invests in the MFS Institutional Money Market Portfolio which is managed by MFS and seeks current income consistent with preservation of capital and liquidity. This money market fund does not pay a management fee to MFS but does incur investment and operating costs.
MFS purchased or redeemed fund shares on the dates indicated: 
Date
Transaction
Class
Shares
Amount
12/31/2025
Purchase
Class B
2,787
$25,000
At April 30, 2026, MFS held approximately 60% and 58% of the outstanding shares of Class B and Class R4, respectively.
(4) Portfolio Securities
For the six months ended April 30, 2026, purchases and sales of investments, other than short-term were as follows: 
 
Purchases
Sales
U.S. Government securities
$131,943,855
$201,045,944
Non-U.S. Government securities
15,260,752
7,118,474
(5) Shares of Beneficial Interest
The fund's Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows: 
 
Six months ended
4/30/26
Year ended
10/31/25
 
Shares
Amount
Shares
Amount
Shares sold
Class A
183,177
$1,662,750
637,370
$5,790,919
Class B
2,787
25,000
—
—
Class C
4,679
41,928
34,249
309,954
Class I
253,627
2,303,805
3,478,202
31,900,300
Class R1
2,131
18,963
3,780
33,453
Class R2
2,516
22,684
6,299
56,844
Class R3
9,077
81,893
18,591
169,061
Class R4
268
2,432
904
8,215
Class R6
2,418,836
22,084,035
18,408,233
167,474,445
 
2,877,098
$26,243,490
22,587,628
$205,743,191
20
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
 
Six months ended
4/30/26
Year ended
10/31/25
 
Shares
Amount
Shares
Amount
Shares issued to shareholders
in reinvestment of distributions
Class A
68,428
$617,220
217,390
$1,967,293
Class B
39
344
276
2,479
Class C
2,519
22,537
7,787
69,903
Class I
44,998
406,298
103,981
945,740
Class R1
866
7,720
2,454
21,944
Class R2
358
3,237
1,177
10,634
Class R3
1,318
11,903
3,661
33,152
Class R4
170
1,531
473
4,284
Class R6
2,372,875
21,495,501
6,997,196
63,605,537
 
2,491,571
$22,566,291
7,334,395
$66,660,966
Shares reacquired
Class A
(611,455
)
$(5,547,545
)
(1,333,202
)
$(12,099,122
)
Class B
(2,356
)
(21,318
)
(14,576
)
(130,720
)
Class C
(87,326
)
(785,566
)
(99,886
)
(896,468
)
Class I
(802,021
)
(7,334,648
)
(962,929
)
(8,771,519
)
Class R1
(5,841
)
(52,046
)
(780
)
(6,988
)
Class R2
(14,209
)
(128,175
)
(12,903
)
(116,406
)
Class R3
(65,699
)
(593,578
)
(5,530
)
(50,261
)
Class R4
(31
)
(287
)
(28
)
(255
)
Class R6
(8,186,191
)
(74,680,391
)
(24,698,271
)
(224,731,666
)
 
(9,775,129
)
$(89,143,554
)
(27,128,105
)
$(246,803,405
)
Net change
Class A
(359,850
)
$(3,267,575
)
(478,442
)
$(4,340,910
)
Class B
470
4,026
(14,300
)
(128,241
)
Class C
(80,128
)
(721,101
)
(57,850
)
(516,611
)
Class I
(503,396
)
(4,624,545
)
2,619,254
24,074,521
Class R1
(2,844
)
(25,363
)
5,454
48,409
Class R2
(11,335
)
(102,254
)
(5,427
)
(48,928
)
Class R3
(55,304
)
(499,782
)
16,722
151,952
Class R4
407
3,676
1,349
12,244
Class R6
(3,394,480
)
(31,100,855
)
707,158
6,348,316
 
(4,406,460
)
$(40,333,773
)
2,793,918
$25,600,752
The fund is one of several mutual funds in which certain MFS funds may invest. The MFS funds do not invest in the underlying funds for the purpose of exercising management or control. At the end of the period, the MFS Moderate Allocation Fund, the MFS Conservative Allocation Fund, the MFS Growth Allocation Fund, the MFS Lifetime 2030 Fund, the MFS Lifetime Income Fund, the MFS Lifetime 2035 Fund, the MFS Lifetime 2040 Fund, the MFS Lifetime 2025 Fund, the MFS Lifetime 2045 Fund, and the MFS Lifetime 2050 Fund were the owners of record of approximately 30%, 24%, 22%, 5%, 3%, 3%, 3%, 2%, 1%, and 1%, respectively, of the value of outstanding voting shares of the fund. In addition, the MFS Lifetime 2055 Fund, the MFS Lifetime 2060 Fund, and the MFS Lifetime 2065 Fund were each the owners of record of less than 1% of the value of outstanding voting shares of the fund.
Effective June 1, 2019, purchases of the fund’s Class B shares were closed to new and existing investors subject to certain exceptions. Effective September 29, 2023, purchases of the fund's Class R1 and Class R2 shares were closed to new eligible investors.
21
MFS Inflation-Adjusted Bond Fund
Notes to Financial Statements (unaudited) - continued 
(6) Line of Credit
The fund and certain other funds managed by MFS participate in a $1.45 billion unsecured committed line of credit of which $1.2 billion is reserved for use by the fund and certain other MFS U.S. funds. The line of credit is provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of 1) Daily Simple SOFR (Secured Overnight Financing Rate), 2) the Federal Funds Effective Rate, or 3) the Overnight Bank Funding Rate, each plus an agreed upon spread. A commitment fee, based on the average daily unused portion of the committed line of credit, is allocated among the participating funds. The line of credit expires on March 11, 2027 unless extended or renewed. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended April 30, 2026, the fund’s commitment fee and interest expense were $3,539 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.
(7) Investments in Affiliated Issuers
An affiliated issuer may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under common control. The following were affiliated issuers for the six months ended April 30, 2026: 
Affiliated Issuers
Beginning
Value
Purchases
Sales
Proceeds
Realized
Gain
(Loss)
Change in
Unrealized
Appreciation
or
Depreciation
Ending
Value
MFS Institutional Money Market
Portfolio
$39,079,284
$166,287,320
$193,493,765
$(8,021
)
$(1,078
)
$11,863,740
 
Affiliated Issuers
Dividend
Income
Capital Gain
Distributions
MFS Institutional Money Market Portfolio
$332,586
$—
22
ITEM 8. CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.
There is nothing to report for this item for MFS Inflation-Adjusted Bond Fund.
ITEM 9.  PROXY DISCLOSURES FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.
There is nothing to report for this item for MFS Inflation-Adjusted Bond Fund.
ITEM 10. REMUNERATION PAID TO DIRECTORS, OFFICERS, AND OTHERS OF OPEN-END MANAGEMENT INVESTMENT COMPANIES.
This information is disclosed as part of the financial statements included in Item 7 above for MFS Inflation-Adjusted Bond Fund. See the Statement of Operations and Note 3 within the Notes to Financial Statements for more information.
ITEM 11. STATEMENT REGARDING BASIS FOR APPROVAL OF INVESTMENT ADVISORY CONTRACT.
Not Applicable.
23


ITEM 12.  DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.


ITEM 13. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES. 

Not applicable to the Registrant.


ITEM 14. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

Not applicable to the Registrant.


ITEM 15. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

There were no material changes to the procedures by which shareholders may send recommendations to the Board for nominees to the Registrant’s Board since the Registrant last provided disclosure as to such procedures in response to the requirements of Item 407 (c)(2)(iv) of Regulation S-K or this Item.


ITEM 16.  CONTROLS AND PROCEDURES.

  • Based upon their evaluation of the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940 (the “Act”)) as conducted within 90 days of the filing date of this report on Form N-CSR, the Registrant’s principal financial officer and principal executive officer have concluded that those disclosure controls and procedures provide reasonable assurance that the material information required to be disclosed by the Registrant on this report is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms.

  • There were no changes in the Registrant’s internal controls over financial reporting (as defined in Rule 30a-3(d) under the Act) that occurred during the period covered by the report that have materially affected, or are reasonably likely to materially affect, the Registrant’s internal control over financial reporting. 


ITEM 17.  DISCLOSURE OF SECURITIES LENDING ACTIVITIES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.


ITEM 18. RECOVERY OF ERRONEOUSLY AWARDED COMPENSATION.

Not applicable to the Registrant.


ITEM 19.  EXHIBITS.

  • Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit:  Not applicable.

  • Any policy required by the listing standards adopted pursuant to Rule 10D-1 under the Exchange Act (17 CFR 240.10D-1) by the registered national securities exchange or registered national securities association upon which the registrant’s securities are listed. Not applicable.

  • A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2):  Attached hereto as EX-99.302CERT.

  • Any written solicitation to purchase securities under Rule 23c-1 under the Act (17 CFR 270.23c-1) sent or given during the period covered by the report by or on behalf of the registrant to 10 or more persons.  Not applicable.

  • Change in the registrant's independent public accountant.  Not applicable.

  • If the report is filed under Section 13(a) or 15(d) of the Exchange Act, provide the certifications required by Rule 30a-2(b) under the Act (17 CFR 270.30a-2(b)), Rule 13a-14(b) or Rule 15d-14(b) under the Exchange Act (17 CFR 240.13a-14(b) or 240.15d-14(b)) and Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. 1350) as an exhibit.  A certification furnished pursuant to this paragraph will not be deemed “filed” for the purposes of Section 18 of the Exchange Act (15 U.S.C. 78r), or otherwise subject to the liability of that section.  Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Exchange Act, except to the extent that the registrant specifically incorporates it by reference. Attached hereto as EX-99.906CERT.


Notice

A copy of the Amended and Restated Declaration of Trust, as amended, of the Registrant is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and the obligations of or arising out of this instrument are not binding upon any of the Trustees or shareholders individually, but are binding only upon the assets and property of the respective constituent series of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant)  MFS SERIES TRUST IX                                                          

By (Signature and Title)*

/S/ DAVID L. DILORENZO

David L. DiLorenzo, President

Date:   June 12, 2026

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*

/S/ DAVID L. DILORENZO

David L. DiLorenzo, President (Principal Executive Officer)

Date:  June 12, 2026

By (Signature and Title)*

/S/ KASEY L. PHILLIPS                                           

Kasey L. Phillips, Treasurer (Principal Financial Officer and Accounting Officer)

Date:  June 12, 2026

*  Print name and title of each signing officer under his or her signature.


ATTACHMENTS / EXHIBITS

ATTACHMENTS / EXHIBITS

99.302

EX-101.SCH

99.906

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