Form 497J MFS SERIES TRUST X

111 Huntington Ave., Boston, Massachusetts 02199-7632

Phone 617-954-5000

December 2, 2022

United States Securities and Exchange Commission

100 F Street, N.E.

Washington, DC  20549

Re:

MFS® Series Trust X (the “Trust”) (File Nos. 33-1657 and 811-4492) on behalf of MFS® Emerging Markets Debt Fund (the "Fund")

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Ladies and Gentlemen:

Pursuant to Rule 497(j) under the Securities Act of 1933, as amended, please accept this letter, on behalf of the Trust, as certification that the Prospectus and the combined Statement of Additional Information for the Fund do not differ from those contained in Post-Effective Amendment No. 171 (the “Amendment”) to the Trust’s Registration Statement on Form N-1A.  The Amendment was filed electronically on November 23, 2022.

Please call the undersigned at (617) 954-5655 or Vanessa Rodriguez-Jimenez at (617) 954-5831 with any questions you may have.

Very truly yours,

WILLIAM B. WILSON

William B. Wilson

Assistant Vice President and Counsel

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