UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

(Mark One)

For the fiscal year ended December 31, 2024

OR

For the transition period from ______________ to _______________

Commission file number 001-35521

CLEARSIGN TECHNOLOGIES CORPORATION

(Exact name of registrant as specified in its charter)

8023 East 63^rd Place, Suite 101

Tulsa, Oklahoma 74133

(Address of principal executive offices)

(Zip Code)

(918) 236-6461

(Registrant’s telephone number, including area code)

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

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

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 x

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 x 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 x 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.

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. ¨

Indicate by check mark whether the issuer is a shell company (as defined in Rule 12b-2 of the Exchange Act).Yes ¨ No x

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 during the relevant recovery period pursuant to §240.10D-1(b). ¨

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.

As of June 30, 2024, the aggregate market value of the voting and non-voting common equity held by non-affiliates of the registrant, computed by reference to the last sale price of the common equity was $33,474,132.

Indicate the number of shares outstanding of each of the registrant’s classes of common stock, as of the latest practicable date.

As of May 28, 2025, the registrant has 52,422,532 shares of common stock, par value $0.0001, issued and outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

None.

Technologies Corporation

TABLE OF CONTENTS

EXPLANATORY NOTE

This Amendment No. 1 (this “Amendment,” or this “report”) amends the Annual Report on Form 10-K for the year ended December 31, 2024 of ClearSign Technologies Corporation (the “Company”), filed with the Securities and Exchange Commission (the “SEC”) on March 31, 2025 (the “Original Form 10-K”). The purpose of this Amendment is to amend “Item 14. Principal Accountant Fees and Services” of Part III of the Original Form 10-K to (i) correct the aggregate fees for professional audit services rendered by BPM CPA LLP (“BPM”), our independent registered public accounting firm, for the audit of the Company’s consolidated financial statements for the years ended December 31, 2024 and 2023, respectively, and fees billed for other services rendered by BPM during those periods; and (ii) reflect in “Audit-Related Fees,” instead of “All Other Fees,” the fees incurred by the Company in connection with certain professional services rendered by BPM relating to certain equity offerings and the filing of proxy statements and registration statements with the SEC. In addition, pursuant to the rules of the SEC, “Item 15. Exhibits and Financial Statement Schedules” of Part III of the Original Form 10-K has been amended to provide currently dated certifications from the Company’s Principal Executive Officer and Principal Financial Officer as required by Sections 302 and 906 of the Sarbanes-Oxley Act of 2002, which are included as Exhibits 31.1, 31.2 and 32.1 hereto.

Except as stated herein, this Amendment does not reflect events occurring after the filing of the Original Form 10-K and no attempt has been made in this Amendment to modify or update other disclosures as presented in the Original Form 10-K.

Unless otherwise stated or the context otherwise requires, the terms “ClearSign,” “we,” “us,” “our” and the “Company” refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

PART III

ITEM 14. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

The following table presents aggregate fees for professional audit services rendered BPM CPA LLP (“BPM”) for the audit of our consolidated financial statements for the years ended December 31, 2024 and 2023, respectively, and fees billed for other services rendered by BPM during those periods.

Audit Fees. “Audit Fees” are the aggregate fees of BPM attributable to professional services rendered in the fiscal years ended December 31, 2024 and 2023 for the audit of our annual consolidated financial statements, for review of condensed consolidated financial statements included in our quarterly reports on Form 10-Q and for services that are normally provided by BPM in connection with statutory and regulatory filings or engagements for those fiscal years.

Audit-Related Fees. “Audit-Related Fees” are attributable to customary agreed upon professional services in connection with our public offering and concurrent private placement in April 2024, “at the market” offering, the filing of registration statements on Form S-3 in August 2023 and Form S-8 in 2024 and 2023, and review of our proxy statements for the annual meetings held on 2024 and 2023.

Pre-approval Policies and Procedures

The Audit Committee is required to review and approve in advance the retention of the independent registered public accounting firm for the performance of all audit and lawfully permitted non-audit services and the fees for such services. The required pre-approval policies and procedures were complied with during 2024 and 2023.

PART IV

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES.

(a) (1) Consolidated Financial Statements

The financial statements required to be filed as part of this report are listed and indexed in the Index to Consolidated Financial Statements on page 33 located in the Original Form 10-K. Financial statement schedules have been omitted because they are not applicable, or the required information has been included elsewhere in the Original Form 10-K.

(a) (2) Financial Statement Schedules

Not applicable.

(a) (3) Exhibits

The exhibits required to be filed by Item 15 are set forth in, and filed with or incorporated by reference in, the “Exhibit Index” of the Original Form 10-K. The attached list of exhibits in the “Exhibit Index” sets forth the additional exhibits required to be filed with this Amendment and are incorporated herein by reference in response to this item.

(b) The exhibits set forth in the following index of exhibits are filed or incorporated by reference as a part of this Amendment:

*Filed herewith.

**Previously filed.

***Furnished herewith.

+Agreement with management or compensatory plan or arrangement

ITEM 16. FORM 10-K SUMMARY.

None.

SIGNATURES

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.

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