UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549

WASHINGTON, D.C. 20549

FORM 10-K

(Mark One)

☒

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, ~~2024~~2025

☐

TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ________ to ________

Commission File Numbers: 333-111858-01, 001-32156 ~~Central Index Key Number: 0001286405~~

Central Index Key Number: 0001286405

Synthetic Fixed-Income Securities, Inc.

on behalf of:

STRATS Trust For United States Cellular Corporation Securities, Series 2004-6 ~~____________________________________________________ (Exact name of registrant as specified in its charter)~~

(Exact name of registrant as specified in its charter)

Delaware	52-2316339
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)

30 Hudson Yards, 14^th Floor, New York, New York	10001-2170
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: (212) 214-6289

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

Title of Each Class		Trading Symbol(s)		Name of Each Exchange on which Registered
STRATS Certificates, Series 2004-6, Class A-1		N/A		New York Stock Exchange (“NYSE”)

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.
☐ Yes ☒ No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.
☐ Yes ☒ No

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.
☒ Yes ☐ No

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

☒ Yes ☐ No

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “"emerging growth company”" in Rule 12b-2 of the Exchange Act.

	Large accelerated filer ☐	Accelerated filer ☐

	Non-accelerated filer ☒	Smaller Reporting Company ☐

		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 complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive ~~officers~~oﬃcers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). ~~☐ Yes ☒ No~~

☐ Yes ☒ No

State the aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant’s most recently completed second fiscal quarter:

The registrant has no voting stock or class of common stock that is held by non-affiliates.

DOCUMENTS INCORPORATED BY REFERENCE

The following documents are incorporated by reference into Part IV of this Annual Report: the distribution reports to security holders filed on Form 8-K during the fiscal year, in lieu of reports on Form 10-Q, which include the reports filed on Form 8-K listed in Item 15(a) hereto.

Introductory Note

Synthetic Fixed-Income Securities, Inc. (the “Depositor”) is the Depositor in respect of the STRATS Trust For United States Cellular Corporation Securities, Series 2004-6 (the “Trust”), a common law trust formed pursuant to the Base Trust Agreement, dated as of September 26, 2003, between the Depositor and U.S. Bank Trust National Association, as trustee (the “Trustee”), as supplemented by the STRATS Certificates Series Supplement 2004-6 (the “Series Supplement”) dated as of April 21, 2004 in respect of the Trust. The Trust’s assets consist solely of notes issued by United States Cellular Corporation. The Certificates do not represent obligations of or interests in the Depositor or the Trustee.

Pursuant to staff administrative positions established in Corporate Asset Backed Corporation (available August 9, 1995), the Trust is not required to respond to various items of Form 10-K. Such items are designated herein as “Not Applicable.” Distribution reports detailing receipts and distributions by the Trust are filed after each distribution date on Form 8-K in lieu of reports on Form 10-Q.

United States Cellular Corporation, the issuer of the underlying securities, is subject to the information reporting requirements of the Securities Exchange Act of 1934, as amended, (the “Exchange Act”). For information on United States Cellular Corporation please see its periodic and current reports filed with the Securities and Exchange Commission (the “Commission”) under its Exchange Act file number, 001-09712. The Commission maintains a site on the World Wide Web at “http://www.sec.gov” at which users can view and download copies of reports, proxy and information statements and other information filed electronically through the Electronic Data Gathering, Analysis and Retrieval system, or “EDGAR.” Periodic and current reports and other information required to be filed pursuant to the Exchange Act, by United States Cellular Corporation may be accessed on this site. Neither Synthetic Fixed-Income Securities, Inc. nor the Trustee has participated in the preparation of such reporting documents, or made any due diligence investigation with respect to the information provided therein. Neither Synthetic Fixed-Income Securities, Inc. nor the Trustee has verified the accuracy or completeness of such documents or reports. There can be no assurance that events affecting the issuer of the underlying securities, or the underlying securities themselves, have not occurred or have not yet been publicly disclosed which would affect the accuracy or completeness of the publicly available documents described above.

PART I

Item 1. Business.

Not Applicable

Item 1A. Risk Factors.

Not Applicable

Item 1B. Unresolved Staff Comments.

Not Applicable

Item 1C. Cybersecurity.

Not Applicable

122

Item 2. Properties.

Not Applicable

Item 3. Legal Proceedings.

None

Item 4. Mine Safety Disclosures.

Not Applicable

PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.

The Class A-1 Certificates representing investors’ interest in the Trust are represented by one or more physical Certificates registered in the name of “Cede & Co.”, the nominee of The Depository Trust Company. The Class A-1 Certificates are listed on the NYSE.

Item 6. [Reserved]

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

Not Applicable

Item 7A. Quantitative and Qualitative Disclosures About Market Risk.

Not Applicable

Item 8. Financial Statements and Supplementary Data.

Not Applicable

Item 9. Changes in and Disagreements With Accountants on Accounting and Financial Disclosure.

None

Item 9A. Controls and Procedures.

Not Applicable

Item 9B. Other Information.

None

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections.

Not Applicable

133

PART III

Item 10. Directors, Executive Officers and Corporate Governance.

Not Applicable

Item 11. Executive Compensation.

Not Applicable

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

Not Applicable

Item 13. Certain Relationships and Related Transactions, and Director Independence.

None

Item 14. Principal Accounting Fees and Services.

Not Applicable

PART IV

Item 15. Exhibit and Financial Statement Schedules.

(a)

List the following documents filed as a part of the report:

1. Trustee’s Distribution Statements documented on Form 8-K of STRATS Trust For United States Cellular Corporation Securities, Series 2004-6 to the certificateholders for the period from January 1, ~~2024~~2025 through and including December 31, ~~2024~~2025 have been filed with the Securities and Exchange Commission and are hereby incorporated by reference. Filing dates are listed below:

Trust Description	Distribution Date	Filed on
STRATS Trust For United States Cellular Corporation Securities, Series 2004-6	06-1716-~~2024~~2025 12-1615-~~2024~~2025	06-2630-~~2024~~2025 12-2619-~~2024~~2025

None

Exhibits:

31.1 – Certification by Director of the Registrant pursuant to 15 U.S.C. Section 7241, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

99.1 – Annual Compliance Report by Trustee pursuant to 15 U.S.C. Section 7241, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

99.2 – Report of Aston Bell, CPA. ~~99.3 - Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on June 26, 2024, as further described in Item 15(a)(1) above, is incorporated herein by reference.~~

1499.3 - Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on June 30, 2025, as further described in Item 15(a)(1) above, is incorporated herein by reference.

~~99.~~4 ~~- Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on December 26, 2024, as further described in Item 15(a)(1) above, is incorporated herein by reference.~~

99.4 - Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on December 19, 2025, as further described in Item 15(a)(1) above, is incorporated herein by reference.

(b)

See Item 15(a) above.

(c)

Not Applicable.

Item 16. Form 10-K Summary.

Not Applicable

155

SIGNATURE

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	Synthetic Fixed-Income Securities, Inc.,
	as Depositor for the Trust

	By:	/s/ Barbara Garafalo
	Name: Barbara Garafalo
	Title: President

Dated: March 3130, ~~2025~~2026

166

EXHIBIT INDEX

Reference Number per Item 601 of Regulation SK	Description of Exhibits	Exhibit Number in this Form 10-K
(31.1)	Certification by Director of the Registrant pursuant to 15 U.S.C. Section 7241, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.	31.1
(99.1)	Annual Compliance Report by Trustee pursuant to 15 U.S.C. Section 7241, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.	99.1
(99.2)	Report of Aston Bell, CPA.	99.2
(99.3)	Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on June 2630, ~~2024~~2026, as further described in Item 15(a)(1) above, is incorporated herein by reference.	99.3
(99.4)	Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission on December 2619, ~~2024~~2025, as further described in Item 15(a)(1) above, is incorporated herein by reference.	99.4

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