UNITED STATES

SECURITIES AND EXCHANGE COMMISION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TOSECTION13OR15(d)OF THESECURITIESEXCHANGEACTOF1934

Date ofReport(Dateofearliesteventreported): March 27, 2026

UNITED STATES COMMODITY INDEX FUNDS TRUST

(Exact name of registrant as specified in its charter)

1850 Mt. Diablo Boulevard, Suite 640

Walnut Creek, California 94596

(Address of principal executive offices) (Zip Code)

(510) 522-9600

Registrant’s telephone number, including area code

Not Applicable

(Former nameorformeraddress,ifchangedsincelastreport)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowingprovisions (seeGeneralInstructionA.2.below):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 ofthischapter)or Rule12b-2oftheSecurities ExchangeAct of1934(§240.12b-2of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complyingwith anynewor revisedfinancialaccounting standardsprovided pursuant to Section13(a)of theExchangeAct. ☐

Securities registered pursuant to Section 12(b) of the Act:

Item 7.01. Regulation FD Disclosure.

On March 27, 2026, each of United States Commodity Index Fund (“USCI”) and United States Copper Index Fund (“CPER”), which are series of the United States Commodity Index Funds Trust (the “Registrant”), issued their annual financial statements for the year ended December 31, 2025, as required pursuant to Rule 4.22 under the Commodity Exchange Act. A copy of the annual financial statements for USCI is furnished as Exhibit 99.1 to this Current Report on Form 8-K and also can be found on USCI’s website at www.uscfinvestments.com. A copy of the annual financial statements for CPER is furnished as Exhibit 99.2 to this Current Report on Form 8-K and also can be found on CPER’s website at www.uscfinvestments.com. The information furnished in this Current Report on Form 8-K, including Exhibit 99.1 and Exhibit 99.2, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in any such filing.

Item 9.01.FinancialStatementsandExhibits.

Exhibit 99.1 Annual Financial Statements of the Registrant for the year ended December 31, 2025.

Exhibit 99.2 Annual Financial Statements of the Registrant for the year ended December 31, 2025.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.