ClearSign Technologies Corp 10-Q

ITEM 1. FINANCIAL STATEMENTS ClearSign Technologies Corporation and Subsidiary Condensed Consolidated Balance Sheets (Unaudited) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands, except share and per share data) ​ March 31, ​ December 31, ​ ​ ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ ASSETS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current Assets: ​ ​ ​ ​ Cash and cash equivalents ​ $ 7,736 ​ $ 9,178 ​ Accounts receivable ​ ​ 171 ​ ​ 1,360 ​ Deferred costs ​ 433 ​ 329 ​ Contract assets ​ ​ 8 ​ ​ — ​ Prepaid expenses and other assets ​ 431 ​ 359 ​ Total current assets ​ 8,779 ​ 11,226 ​ ​ ​ ​ ​ ​ ​ ​ ​ Fixed assets, net ​ 166 ​ 195 ​ Contract assets ​ ​ 127 ​ ​ — ​ Patents and other intangible assets, net ​ 764 ​ 760 ​ Total Assets ​ $ 9,836 ​ $ 12,181 ​ ​ ​ ​ ​ ​ ​ ​ ​ LIABILITIES AND STOCKHOLDERS' EQUITY ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current Liabilities: ​ ​ ​ ​ ​ Accounts payable and accrued liabilities ​ $ 1,752 ​ $ 1,644 ​ Current portion of lease liabilities ​ 98 ​ 96 ​ Accrued compensation and related taxes ​ 257 ​ 564 ​ Contract liabilities ​ ​ 63 ​ ​ 100 ​ Other current liabilities ​ ​ — ​ ​ 180 ​ Total current liabilities ​ 2,170 ​ 2,584 ​ Long Term Liabilities: ​ ​ ​ ​ ​ Long term lease liabilities ​ 42 ​ ​ 67 ​ Total liabilities ​ 2,212 ​ 2,651 ​ ​ ​ ​ ​ ​ ​ ​ ​ Commitments and contingencies (Note 10) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stockholders’ Equity: ​ ​ ​ ​ ​ Preferred stock, $ 0.0001 par value, 2,000,000 shares authorized, no shares issued or outstanding ​ — ​ — ​ Common stock, $ 0.0001 par value, 87,500,000 shares authorized, 5,409,133 and 5,328,730 shares issued and outstanding at March 31, 2026 and December 31, 2025, respectively. ​ 1 ​ ​ 1 ​ Additional paid-in capital ​ 114,343 ​ ​ 114,061 ​ Accumulated other comprehensive loss ​ ​ ( 18 ) ​ ​ ( 20 ) ​ Accumulated deficit ​ ( 106,702 ) ​ ​ ( 104,512 ) ​ Total stockholders' equity ​ 7,624 ​ 9,530 ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Liabilities and Stockholders' Equity ​ $ 9,836 ​ $ 12,181 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The accompanying notes are an integral part of these unaudited condensed consolidated financial statements. ​ 1 Table of Contents ​ ClearSign Technologies Corporation and Subsidiary Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands, except share and per share data) ​ For the Three Months Ended ​ ​ ​ March 31, ​ ​ ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 191 ​ $ 401 ​ Cost of goods sold ​ 584 ​ 205 ​ Gross profit (loss) ​ ( 393 ) ​ 196 ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ Research and development ​ 249 ​ 447 ​ General and administrative ​ 1,637 ​ 2,006 ​ Total operating expenses ​ 1,886 ​ 2,453 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss from operations ​ ( 2,279 ) ​ ( 2,257 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Other income, net: ​ ​ ​ ​ ​ ​ ​ Interest income ​ ​ 62 ​ ​ 133 ​ Government assistance ​ ​ 28 ​ ​ 48 ​ Other income, net ​ ​ ( 1 ) ​ ​ — ​ Total other income, net ​ 89 ​ 181 ​ Net loss ​ $ ( 2,190 ) ​ $ ( 2,076 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share - basic and fully diluted ​ $ ( 0.39 ) ​ $ ( 0.38 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of shares outstanding - basic and fully diluted ​ 5,627,127 ​ 5,499,598 ​ ​ ​ ​ ​ ​ ​ ​ ​ Comprehensive loss: ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ ( 2,190 ) ​ $ ( 2,076 ) ​ Foreign-exchange translation adjustments ​ ​ 2 ​ ​ — ​ Comprehensive loss ​ $ ( 2,188 ) ​ $ ( 2,076 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The accompanying notes are an integral part of these unaudited condensed consolidated financial statements. ​ 2 Table of Contents ClearSign Technologies Corporation and Subsidiary Condensed Consolidated Statements of Stockholders’ Equity For the Three Months Ended March 31, 2026 and 2025 (Unaudited) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated Other ​ ​ ​ ​ Total (in thousands) ​ Common Stock ​ Additional ​ Comprehensive ​ Accumulated ​ Stockholders’ ​ ​ Shares ​ Amount ​ Paid-In Capital ​ ​ Loss ​ Deficit ​ Equity Balances at December 31, 2025 5,328 ​ $ 1 ​ $ 114,061 ​ $ ( 20 ) ​ $ ( 104,512 ) ​ $ 9,530 Share-based compensation, net of tax withholdings ​ 11 ​ ​ — ​ ​ 76 ​ ​ — ​ ​ — ​ ​ 76 Fair value of stock issued in payment of accrued compensation ​ 36 ​ ​ — ​ ​ 203 ​ ​ — ​ ​ — ​ ​ 203 Shares issued for services ​ 1 ​ ​ — ​ ​ 3 ​ ​ — ​ ​ — ​ ​ 3 Exercise of prefunded warrants ​ 33 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Foreign-exchange translation adjustment ​ — ​ ​ — ​ ​ — ​ ​ 2 ​ ​ — ​ ​ 2 Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 2,190 ) ​ ​ ( 2,190 ) Balances at March 31, 2026 ​ 5,409 ​ $ 1 ​ $ 114,343 ​ $ ( 18 ) ​ $ ( 106,702 ) ​ $ 7,624 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated Other ​ ​ ​ ​ ​ Total (in thousands) ​ Common Stock ​ Additional ​ Comprehensive ​ Accumulated ​ Stockholders' ​ ​ Shares ​ Amount ​ Paid-In Capital ​ ​ Loss ​ Deficit ​ Equity Balances at December 31, 2024 ​ 5,028 ​ $ 1 ​ $ 112,800 ​ $ ( 21 ) ​ $ ( 99,016 ) ​ $ 13,764 Share-based compensation, net of tax withholdings ​ 8 ​ ​ — ​ ​ 45 ​ ​ — ​ ​ — ​ ​ 45 Fair value of stock issued in payment of accrued compensation 33 ​ ​ — ​ ​ 279 ​ ​ — ​ ​ — ​ ​ 279 Shares issued for services ​ 1 ​ ​ — ​ ​ 4 ​ ​ — ​ ​ — ​ ​ 4 Exercise of warrants ​ 2 ​ ​ — ​ ​ 24 ​ ​ — ​ ​ — ​ ​ 24 Exercise of prefunded warrants ​ 170 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 2,076 ) ​ ​ ( 2,076 ) Balances at March 31, 2025 ​ 5,242 ​ $ 1 ​ $ 113,152 ​ $ ( 21 ) ​ $ ( 101,092 ) ​ $ 12,040 ​ The accompanying notes are an integral part of these unaudited condensed consolidated financial statements. ​ 3 Table of Contents ClearSign Technologies Corporation and Subsidiary Condensed Consolidated Statements of Cash Flows (Unaudited) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) ​ For the Three Months Ended March 31, ​ ​ ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ Cash flows from operating activities: ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ ( 2,190 ) ​ $ ( 2,076 ) ​ Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ Common stock issued for services ​ 3 ​ ​ 4 ​ Share-based compensation, net of tax withholdings ​ 76 ​ ​ 45 ​ Depreciation and amortization ​ 43 ​ ​ 47 ​ Impairment of intangible assets ​ ​ 23 ​ ​ — ​ Right-of-use asset amortization ​ 22 ​ ​ 22 ​ Change in operating assets and liabilities: ​ ​ ​ ​ ​ ​ Deferred costs ​ ( 104 ) ​ ​ ( 253 ) ​ Accounts receivable ​ 1,189 ​ ​ 30 ​ Prepaid expenses and other assets ​ ( 72 ) ​ ​ 110 ​ Contract assets ​ ​ ( 135 ) ​ ​ — ​ Accounts payable, accrued liabilities, and lease liabilities ​ 117 ​ ​ ( 33 ) ​ Other current liabilities ​ ​ ( 180 ) ​ ​ — ​ Accrued compensation and related taxes ​ ( 102 ) ​ ​ ( 118 ) ​ Contract liabilities ​ ​ ( 38 ) ​ ​ 1,111 ​ Net cash used in operating activities ​ ( 1,348 ) ​ ( 1,111 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash flows from investing activities: ​ ​ ​ ​ ​ Acquisition of fixed assets ​ — ​ ​ ( 4 ) ​ Disbursements for patents and other intangible assets ​ ( 64 ) ​ ​ ( 37 ) ​ Net cash used in investing activities ​ ( 64 ) ​ ( 41 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash flows from financing activities: ​ ​ ​ ​ ​ Proceeds from exercise of warrants ​ ​ — ​ ​ 24 ​ Taxes paid related to employee stock awards ​ ​ ( 32 ) ​ ​ ( 41 ) ​ Net cash used in financing activities ​ ( 32 ) ​ ( 17 ) ​ Effect of exchange rate changes on cash and cash equivalents ​ ​ 2 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Net change in cash and cash equivalents ​ ( 1,442 ) ​ ​ ( 1,169 ) ​ Cash and cash equivalents, beginning of period ​ 9,178 ​ ​ 14,035 ​ Cash and cash equivalents, end of period ​ $ 7,736 ​ $ 12,866 ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of cash flow information: ​ ​ ​ ​ ​ ​ ​ Officer and employee equity awards for prior year accrued compensation ​ $ 203 ​ $ 279 ​ ​ The accompanying notes are an integral part of these unaudited condensed consolidated financial statements. ​ 4 Table of Contents ClearSign Technologies Corporation Notes to Unaudited Condensed Consolidated Financial Statements Note 1 – Organization and Description of Business ClearSign Technologies Corporation (“ClearSign” or the “Company”) designs and develops products and technologies for the purpose of decarbonization and improving key performance characteristics of industrial and commercial systems, including operational performance, energy efficiency, emission reduction, safety, and overall cost-effectiveness. The Company’s patented technologies are designed to be embedded in established original equipment manufacturers (“OEM”) products as ClearSign Core™ and ClearSign Eye and other sensing configurations in order to enhance the performance of combustion systems and fuel safety systems in a broad range of markets. These markets include energy (upstream oil production and downstream refining), commercial/industrial boiler, chemical, petrochemical, transport and power industries. The Company’s primary technology is its ClearSign Core™ technology, which achieves very low emissions without the need of selective catalytic reduction. The Company was originally incorporated in the State of Washington in 2008. During January 2022, the Company relocated its headquarters from Seattle, Washington to Tulsa, Oklahoma. Effective June 15, 2023, the Company changed its state of incorporation to Delaware. On July 28, 2017, the Company incorporated a subsidiary, ClearSign Asia Limited, in Hong Kong to represent the Company’s business and technological interests throughout Asia. Through ClearSign Asia Limited, the Company has established a wholly foreign owned enterprise in China – ClearSign Combustion (Beijing) Environmental Technologies Co., LTD. On August 22, 2024, the Company’s Board of Directors (the “Board”) authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years . The Company can revive its China operations at any time during those three years with minimal cost impact. The effective date of our dormancy filing was March 12, 2025. Unless otherwise stated or the context otherwise requires, the terms “we,” “us,” “our,” “ClearSign” and the “Company” refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited. Business Segments The Company operates in one operating and reportable segment engaged in the design, development and sale of combustion technologies that improve the performance and cost-effectiveness of industrial combustion systems, referred to herein as the “Combustion” segment. The Company manages its business activities on a consolidated basis. Since the operations comprise a single reportable segment, amounts reported in the consolidated balance sheets, statements of operations and comprehensive loss, stockholders’ equity, and cash flows represent the activities of the Combustion segment. ​ The Combustion segment derives revenues by delivering products and technology solutions to OEMs and end-users. Our products and solutions can be incorporated into a new or existing customer infrastructure or equipment. Customer contracts can include multiple billing milestones and performance obligations. The Company can typically satisfy its performance obligations within a twelve-month period, but customer project delays, some of which can be beyond the Company’s control, can impact timing of performance and there is no assurance we will satisfy all performance obligations in such period of time. ​ The Company’s Chief Executive Officer, who is the chief operating decision-maker (“CODM”), reviews quarterly and annual financial information on a consolidated basis for making operating decisions, allocating resources and evaluating financial performance. The CODM consistently reviews the consolidated statements of operations and comprehensive loss to manage operations and monitor performance against management expectations. Factors considered by the CODM when assessing a reportable segment include factors such as, but not limited to, human capital, intellectual property, customer relationships and business model design. ​ Substantially all the Company’s operating activities, including its long-lived assets, are located within the United States. Customers in the United States accounted for 100 % of revenues during the three months ended March 31, 2026 and 2025. The Company disaggregates geographical revenues by selling location, since many of our target customers are 5 Table of Contents global entities, and it would be more likely than not, that these customers would negotiate sales within our current territory in the United States. ​ Note 2 – Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting on Form 10-Q. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet at December 31, 2025 has been derived from the Company’s audited consolidated financial statements as of that date. In the opinion of management, these unaudited condensed consolidated financial statements reflect all normal recurring and other adjustments necessary for a fair presentation. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025 (the “Form 10-K”). Operating results for interim periods are not necessarily indicative of operating results for an entire fiscal year or any other future periods. The accompanying unaudited condensed consolidated financial statements include the accounts of ClearSign and its subsidiary. Intercompany balances and transactions have been eliminated in consolidation. Reverse Stock Split On March 6, 2026, the Company filed a certificate of amendment to its certificate of incorporation, as amended, with the Secretary of State of the State of Delaware to effect a 1-for-10 reverse stock split of the Company’s shares of common stock, which became effective at 12:01 a.m. Eastern Time on March 16, 2026. Such amendment and reverse stock split ratio were previously approved by the Company’s stockholders and Board. As a result of the reverse stock split, which was effective for trading purposes on March 16, 2026, every 10 shares of the Company’s pre-reverse split outstanding common stock were combined and reclassified into one share of common stock. Proportionate voting rights and other rights of holders of common stock, par value and shares authorized were not affected by the reverse stock split. Any fractional shares of common stock resulting from the reverse stock split were rounded up to the nearest whole share at the participant level with the Depository Trust Company. All stock options and restricted stock units outstanding and common stock reserved for issuance under the Company’s equity incentive plans and warrants outstanding immediately prior to the reverse stock split were proportionately adjusted, and the exercise prices were proportionately increased, as a result of the reverse stock split. All share and per-share amounts in these unaudited condensed consolidated financial statements have been restated to reflect the reverse stock split as if it had occurred at the beginning of the earliest period presented. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Product Warranties The Company warrants all installed products against defects in materials and workmanship for a period specified in each contract by replacing failed parts. Accruals for product warranties are based on historical or expected warranty experience and current product performance trends and are recorded as a component of cost of sales at the time revenue is recognized. The warranty liabilities are reduced by material and labor costs used to replace parts over the warranty period in the periods in which the costs are incurred. The Company periodically assesses the adequacy of its recorded 6 Table of Contents warranty liabilities and adjusts the amounts as necessary, and such adjustments could be material in the future if estimates differ significantly from actual warranty expense. Product warranties are included in accounts payable and accrued liabilities in the condensed consolidated balance sheets. Although a warranty is a type of guarantee, assurance-type warranties are not subject to the general recognition provisions of Accounting Standards Codification (“ASC”) Topic 460, Guarantees , which requires recognizing guarantees at fair value. Research and Development The cost of research and development is expensed as incurred. Research and development costs consist of salaries, benefits, share-based compensation, consumables, and consulting fees, including costs to develop and test prototype equipment and parts. Research and development costs have been offset by funds received, if any, from strategic partners in cost sharing and/or collaborative projects. During the three months ended March 31, 2026 and 2025, the Company received $ 115 thousand and zero , respectively, from these types of arrangements. ​ Foreign Operations The accompanying unaudited condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025 include assets amounting to approximately $ 149 thousand and $ 175 thousand, respectively, relating to the operations of ClearSign Asia Limited. The Beijing registered capital requirement is $ 350 thousand, which is required to be paid by June 30, 2032, and of which $ 261 thousand has been paid as of March 31, 2026. On August 22, 2024, the Board authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years . The Company can revive its China operations at any time during those three years with minimal cost impact. The dormancy filing became effective as of March 12, 2025. Recently Issued Accounting Pronouncements In November 2024, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40) (“ASU 2024-03”). ASU 2024-03 requires enhanced disclosures about types of expenses, including purchases of inventory, employee compensation, depreciation, and amortization, in commonly presented expense captions. The amendments are effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. Entities may apply the amendments prospectively or retrospectively to any or all prior periods presented in the financial statements. We are currently evaluating the impact that this guidance will have on the disclosures within our consolidated financial statements. While ASU 2024-03 will impact only our disclosures and not our financial condition and results of operations, we are assessing when we will adopt the ASU 2024-03. In May 2025, FASB issued ASU No. 2025-04, Compensation—Stock Compensation (Topic 718) and Revenue from Contracts with Customers (“Topic 606”): Clarifications to Share-Based Consideration Payable to a Customer (“ASU 2025-04”), which clarifies the guidance on the accounting for share-based payment awards that are granted by an entity as consideration payable to its customer, with the intent to reduce diversity in practice and improve existing guidance by revising the definition of a “performance condition” and eliminating a forfeiture policy election for service conditions associated with share-based consideration payable to a customer. ASU 2025-04 also clarifies the guidance in Topic 606 on the variable consideration constraint does not apply to share-based consideration payable to a customer “regardless of whether an award’s grant date has occurred.” ASU 2025-04 is effective for our reporting period beginning January 1, 2027, with early adoption permitted. We are currently assessing the impact that the adoption of ASU 2025-04 will have on the disclosures in our annual consolidated financial statements. ​ In December 2025 , FASB issued ASU No. 2025-11 , "Interim Reporting (Topic 270): Narrow-Scope Improvements.” ASU 2025-11 is intended to provide clarity about the current interim reporting requirements, provides a list of the interim disclosures required by all other Codification topics and establishes a disclosure principle that requires entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. ASC 2025-11 will be effective for the Company beginning January 1, 2028, with early adoption permitted, and is not expected to have a significant impact on the Company’s condensed consolidated financial statements. ​ 7 Table of Contents In December 2025, the FASB issued ASU No. 2025-10, "Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities" (“ASU 2025-10”). The FASB issued ASU 2025-10 to establish authoritative guidance on the accounting for government grants received by business entities. ASU 2025-10 is effective for our annual and quarterly reporting periods beginning January 1, 2029. Early adoption is permitted. We are currently assessing the impact that the adoption of ASU 2025-10 will have on our consolidated financial statements. ​ ​ ​ Note 3 – Fixed Assets, Net Fixed Assets, Net Fixed assets, net are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ (in thousands) ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ Office furniture and equipment ​ $ 103 ​ $ 103 ​ Leasehold improvements ​ 43 ​ 43 ​ ​ ​ ​ 146 ​ ​ 146 ​ Accumulated depreciation and amortization ​ ( 115 ) ​ ( 108 ) ​ ​ ​ ​ 31 ​ ​ 38 ​ Operating lease ROU assets, net ​ ​ 135 ​ ​ 157 ​ Total ​ $ 166 ​ $ 195 ​ ​ Depreciation expense related to office furniture, equipment and leasehold improvements for the three months ended March 31, 2026 and 2025 was $ 6 thousand and $ 5 thousand, respectively. Leases The Company leases office space in Tulsa, Oklahoma, Seattle, Washington, and Beijing, China. During May 2025, the Company renewed its Beijing, China lease for 24 months with monthly rent at approximately $ 3 thousand. As a result of this renewal, the Company increased the right-of-use (“ROU”) asset and lease liability by $ 68 thousand during the year ended December 31, 2025. ​ During October 2024, the Company entered into a sub-lease agreement to re nt office space in Seattle for approximately $ 2 thousand per month for twelve months . The Seattle lease is considered a short-term lease, as the lease term is 12 months or less from the commencement date. The Seattle lease was renewed in October 2025 with similar terms. The short-term lease expense for the three months ended March 31, 2026 and 2025 was approximately $ 6 thousand. The Tulsa and Beijing leases are classified as operating leases, each with remaining terms of less than two years ; contractual language requires renewal negotiations to occur at or near termination. These leases are normal and customary for office space, in that, contractual guarantees exist requiring the lessee return the premises to its original functional state. ​ The Tulsa lease contains fixed annual lease payments that increase annually by approximately 2 %. The Seattle, Tulsa, and Beijing total monthly minimum rent is approximately $ 10 thousand. Operating lease costs for the three months ended March 31, 2026 and 2025 were $ 25 thousand and $ 24 thousand, respectively. 8 Table of Contents Supplemental balance sheet information related to operating leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ ​ December 31, ​ (in thousands) ​ ​ 2026 ​ ​ 2025 ​ Operating lease ROU assets, net ​ $ 135 ​ $ 157 ​ Lease Liabilities: ​ ​ ​ ​ ​ ​ ​ Current lease liabilities ​ $ 98 ​ $ 96 ​ Long term lease liabilities ​ ​ 42 ​ ​ 67 ​ Total lease liabilities ​ $ 140 ​ $ 163 ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average remaining lease term (in years): ​ 1.4 ​ ​ 1.7 ​ Weighted average discount rate: ​ 4.4 % ​ 4.4 % ​ ​ Supplemental cash flow information related to operating leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Three Months Ended ​ ​ March 31, (in thousands) ​ ​ 2026 ​ ​ 2025 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash flows used in operating leases ​ $ 25 ​ $ 25 ​ Minimum future payments under the Company’s operating lease liabilities as of March 31, 2026 are as follows: ​ ​ ​ ​ ​ (in thousands) ​ ​ ​ ​ ​ 2026 (remaining) $ 76 2027 ​ 69 Total future lease payments ​ ​ 145 Less: imputed interest ​ ​ ( 5 ) ​ ​ $ 140 ​ ​ ​ ​ Note 4 – Patents and Other Intangible Assets, Net Patents and other intangible assets, net are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ (in thousands) ​ ​ ​ 2026 ​ ​ ​ 2025 ​ ​ ​ Patents ​ ​ ​ ​ ​ ​ ​ Patents pending ​ $ 386 ​ $ 358 ​ Issued patents ​ 1,095 ​ 1,110 ​ ​ ​ 1,481 ​ 1,468 ​ Trademarks ​ ​ ​ ​ ​ Registered trademarks ​ 86 ​ 86 ​ ​ ​ 86 ​ 86 ​ Other ​ 8 ​ 8 ​ ​ ​ 1,575 ​ 1,562 ​ Accumulated amortization ​ ( 811 ) ​ ( 802 ) ​ ​ ​ $ 764 ​ $ 760 ​ ​ 9 Table of Contents Amortization expense for the three months ended March 31, 2026 and 2025 was $ 37 thousand and $ 42 thousand, respectively. ​ Future amortization expense associated with issued patents and registered trademarks as of March 31, 2026 is as follows: ​ ​ ​ ​ ​ (in thousands) ​ ​ ​ 2026 (remaining) ​ $ 104 2027 ​ 116 2028 ​ 82 2029 ​ 48 2030 ​ ​ 19 Thereafter ​ 1 ​ ​ $ 370 ​ The amortization life for patents ranges between three to five years and trademark lives are set at ten years . The Company does not amortize patents or trademarks classified as pending. ​ During the three months ended March 31, 2026 and 2025, the Company assessed its patent and trademark assets. During the three months ended March 31, 2026 and 2025, we recorded impairments of $ 23 thousand and zero , respectively. These impairment costs are included within research and development in the unaudited condensed consolidated statements of operations and comprehensive loss. The Company also evaluated its strategic approach to the pursuit and protection of its intellectual property. It is the intent of the Company to continue to pursue intellectual property protection. If the Company identifies certain assets where the intellectual property does not directly align with its core technology, the Company will impair the intangible asset and write-off the asset as an expense. ​ ​ Note 5 – Revenue, Contract Assets, and Contract Liabilities The Company’s contracts with customers generally have performance obligations and a schedule of non-refundable cancellation obligations. Performance obligations typically fall into one of three categories: product shipment, customer witness tests, and engineering services, such as delivery of Computational Fluid Dynamic (“CFD”) studies, engineering documents, and engineering consultation. Customer payment milestones are unique to individual contracts and may occur prior to completion of performance obligations. Customer payment terms typically range between thirty and sixty days from the date of billing. Our customer contracts typically have a duration of less than twelve months . Delays in contract performance, if any, typically occur as a result of customer onsite project delays outside of our control. ​ The Company recognized $ 191 thousand of revenues and $ 584 thousand of cost of goods sold during the three months ended March 31, 2026. The revenue and cost of goods sold predominately relates to our mid-stream and boiler burner product offerings. The cost of goods sold is comprised of two components: (i) costs related to our revenue and (ii) costs related to a warranty accrual estimate (refer to “Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations – Results of Operation” below for further details). The product offerings associated with the recognized revenue constitute performance obligations. ​ The Company recognized $ 401 thousand of revenues and $ 205 thousand of cost of goods sold during the three months ended March 31, 2025. The revenue and cost of goods sold predominantly relate to multiple spare parts orders for a single customer. Additionally, the Company successfully completed a CFD engineering study and sold a single boiler burner. The product offerings associated with the recognized revenue constitute performance obligations. ​ The Company had contract assets of $ 135 thousand and zero at March 31, 2026 and December 31, 2025, respectively. The Company had contract liabilities of $ 63 thousand and $ 100 thousand at March 31, 2026 and December 31, 2025, respectively. Of the $ 100 thousand contract liabilities balance at December 31, 2025, the Company recognized revenue of $ 49 thousand during the three months ended March 31, 2026. ​ 10 Table of Contents Note 6 – Deferred Costs ​ A summary of the Company’s deferred costs activity in the accompanying unaudited condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, (in thousands) ​ 2026 ​ 2025 Deferred costs at beginning of year ​ $ 329 ​ $ 562 Capitalization ​ ​ ​ ​ ​ ​ Labor and overhead allocations ​ ​ 66 ​ ​ 484 Supplier and subcontractor costs ​ ​ 195 ​ ​ 2,284 ​ ​ ​ 261 ​ ​ 2,768 Amortization of deferred costs ​ ​ ( 142 ) ​ ​ ( 2,996 ) Impairment of costs in excess of contractual value ​ ​ ( 15 ) ​ ​ ( 5 ) Deferred costs at end of period ​ $ 433 ​ $ 329 ​ ​ ​ Note 7 – Product Warranties ​ A summary of the Company’s warranty liability activity, which is included in accounts payable and accrued liabilities in the accompanying unaudited condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ (in thousands) ​ 2026 ​ ​ ​ 2025 ​ ​ ​ Warranty liability at beginning of year ​ $ 792 ​ $ 471 ​ Accruals ​ 427 ​ 840 ​ Payments ​ ( 111 ) ​ ( 488 ) ​ Changes related to expirations and settlements ​ ​ - ​ ​ ( 31 ) ​ Warranty liability at end of period ​ $ 1,108 ​ $ 792 ​ ​ ​ Note 8 – Equity Common Stock and Preferred Stock The Company is authorized to issue 87.5 million shares of common stock and 2.0 million shares of preferred stock. Preferences, limitations, voting powers and relative rights of any preferred stock to be issued may be determined by the Board. The Company has not issued any shares of preferred stock. The Company has an At-The-Market (“ATM”) program pursuant to an ATM Offering Agreement with H.C. Wainwright & Co., LLC (“Wainwright”) as sales agent, dated July 17, 2025 (the “Sales Agreement”), pursuant to which the Company may offer and sell shares of common stock with an aggregate offering price of up to approximately $ 10.4 million. As of the date of this report, no shares have been sold pursuant to the Sales Agreement. ​ The Company is currently subject to the SEC’s “baby shelf rules,” which prohibit companies with a public float of less than $75 million from issuing securities under a “shelf” registration statement in excess of one-third of such company’s public float in a 12-month period. These rules may limit future issuances of shares by the Company under our “shelf” registration statement on Form S-3, including through the ATM program with Wainwright or other securities offerings. Warrants and Pre-Funded Warrants ​ The following table summarizes the activity and outstanding balance of our outstanding warrants and pre-funded warrants as of March 31, 2026, along with the associated weighted average exercise price and weighted average remaining life for such warrants and pre-funded warrants. ​ 11 Table of Contents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2026 ​ ​ Warrants ​ Pre-Funded Warrants (1) ( in thousands, except per share data ) ​ Number ​ Wtd. Avg. Exercise Price ​ Wtd. Avg. Remaining Life (in years) ​ Aggregate Intrinsic Value ​ Number ​ Wtd. Avg. Exercise Price ​ Aggregate Intrinsic Value Outstanding at beginning of year ​ 2,128 $ 10.54 ​ 3.37 $ — ​ 280 $ 0.001 $ 1,554 Granted ​ — ​ — ​ ​ ​ ​ ​ — ​ — ​ ​ Exercised ​ — ​ — ​ ​ ​ ​ ​ ( 33 ) ​ 0.001 ​ ​ Forfeited/Expired ​ — ​ — ​ ​ ​ ​ ​ — ​ — ​ ​ Outstanding at end of period ​ 2,128 $ 10.54 ​ 3.12 $ — ​ 247 $ 0.001 $ 1,075 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) The pre-funded warrants have no expiration date and only expire when exercised in full. ​ ​ ​ Refer to the Form 10-K for additional details related to our outstanding warrants and pre-funded warrants. Equity Incentive Plan On June 17, 2021, the Company's stockholders approved and the Company adopted the ClearSign Technologies Corporation 2021 Equity Incentive Plan (as it may be amended from time to time, the “2021 Plan”) which permits the Company to grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and performance shares, to eligible participants, which includes employees, directors and consultants. The Board’s Human Capital and Compensation Committee (the “Compensation Committee”) is authorized to administer the 2021 Plan. ​ The 2021 Plan provides for an annual increase in available shares equal to the lesser of (i) 10 % of the aggregate number of shares of common stock issued by the Company in the prior fiscal year; or (ii) such number provided by the Compensation Committee; provided, however, that the total cumulative increase in the number of shares available for issuance pursuant to this automatic share increase shall not exceed 40 thousand shares of common stock. In 2025, the Board did not exercise their right to limit the automatic increase. Accordingly, the 2021 Plan share reserve increased by 40 thousand shares. ​ Ending balances for the 2021 Plan is as follows: ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ( in thousands ) ​ ​ ​ 2026 ​ ​ ​ 2025 Outstanding options and restricted stock units 303 291 Reserved but unissued shares under the 2021 Plan ​ 120 ​ 149 Reserved but unissued shares at end of period 423 440 ​ Stock Options ​ Under the terms of the 2021 Plan, incentive stock options and non-statutory stock options must have an exercise price at or above the fair market value on the date of the grant. At the time of grant, the Company will determine the period within which the option may be exercised and will specify any conditions that must be satisfied before the option vests and may be exercised. The Company estimates the fair value of stock options on the date of grant using the Black-Scholes option pricing model. ​ As permitted by SEC Staff Accounting Bulletin 107, management utilized the simplified approach to estimate the expected term of the options, which represents the period of time that options granted are expected to be outstanding. Expected volatility has been determined through the Company’s historical stock price volatility. The Company has not made an estimate of forfeitures at the time of the grant, but rather accounts for forfeitures at the time they occur. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield in effect at the time of grant. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future. ​ 12 Table of Contents During the three months ended March 31, 2026, the following weighted-average assumptions were utilized in the calculation of the fair market value of stock options granted: ​ ​ ​ ​ ​ ​ ​ March 31, ​ ​ 2026 Expected life ​ ​ ​ 5.00 years Weighted average volatility ​ 99.28 % Forfeiture rate ​ 0 % Weighted average risk-free interest rate ​ 3.97 % Expected dividend rate ​ 0 % ​ No stock options were granted during the three months ended March 31, 2025. ​ Equity Incentive Plan Options ​ Compensation expense associated with stock option awards for the three months ended March 31, 2026 and 2025 totaled $ 46 thousand and $ 20 thousand, respectively. ​ A summary of the Company’s 2011 Equity Incentive Plan and the 2021 Plan stock option activity and changes is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ ​ 2026 ( in thousands, except per share data ) ​ Options to Purchase Common Stock ​ Weighted Average Exercise Price ​ Weighted Average Remaining Contractual Life (in years) ​ Aggregate Intrinsic Value Outstanding at beginning of year 238 ​ $ 20.24 3.64 $ 855 Granted 9 ​ $ 4.36 ​ ​ ​ Exercised — ​ $ — ​ ​ ​ Forfeited/expired ( 18 ) ​ $ 16.69 ​ ​ ​ Outstanding at end of period 229 ​ $ 19.89 3.93 $ — Exercisable at end of period 176 ​ $ 16.24 3.66 $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The intrinsic value is the difference between the Company’s common stock price and the option exercise prices multiplied by the number of in-the-money options. This amount changes based on the fair value of the Company’s common stock. ​ At March 31, 2026, there was $ 234 thousand of total unrecognized compensation cost related to non-vested stock option-based compensation arrangements. Vesting criteria ranges from time-based to performance-based. The Company records costs for time-based arrangements ratably across the timeframe, whereas performance-based arrangements require management to continually evaluate predetermined goals against actual circumstances. The maximum contractual term for these options is ten years from the grant date. ​ Inducement Options ​ The inducement options summarized below were granted outside of the 2021 Plan and in accordance with the employment inducement exemption provided under Nasdaq Listing Rule 5635(c)(4). The compensation expense recognized for the inducement options for the three months ended March 31, 2026 and 2025 was zero and $ 9 thousand, respectively. ​ 13 Table of Contents A summary of the Company’s inducement option activity and changes is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ ​ 2026 ( in thousands, except per share data ) ​ Options to Purchase Common Stock ​ Weighted Average Exercise Price ​ Weighted Average Remaining Contractual Life (in years) ​ Aggregate Intrinsic Value Outstanding at beginning of year 49 ​ $ 15.27 4.53 $ — Granted — ​ $ — ​ ​ ​ Exercised — ​ $ — ​ ​ ​ Forfeited/expired — ​ $ — ​ ​ ​ Outstanding at end of period 49 ​ $ 15.27 4.24 $ — Exercisable at end of period 49 ​ $ 15.27 4.24 $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted Stock Units The Company awards its directors and certain employees restricted stock units (“RSUs”) in lieu of cash payment for compensation, if such non-executive directors elect to receive RSUs in lieu of cash payment as allowed by the Company’s director compensation policy. These awards are granted pursuant to the 2021 Plan. Employee vesting criteria are time-based, and compensation expense is recognized ratably across the timeframe. The Company pays payroll withholding taxes on behalf of the employee at vesting by withholding shares from the employee’s award to cover taxes payable in connection with such vesting. The Company accrued taxes for RSU share-based compensation of $ 6 thousand and $ 8 thousand for the three months ended March 31, 2026 and 2025, respectively. Total unrecognized compensation expense for employee restricted stock units as of March 31, 2026 was $ 336 thousand. Director vesting criteria are contingent upon the occurrence of one of four future events, which the Company cannot predict or control. Therefore, compensation expense for director RSUs is not recognized until one of these four future events occurs in accordance with FASB ASC Topic 718 , “Compensation – Stock Compensation.” Total unrecognized compensation expense for director services as of March 31, 2026 was $ 154 thousand. A summary of the Company’s RSUs activity is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ ​ 2026 ( in thousands, except per share data ) ​ Number of Shares ​ Weighted Average Grant Date Fair Value ​ Weighted Average Contractual Life (in years) (1) Nonvested at beginning of year 53 ​ $ 8.36 ​ 0.85 Granted 38 ​ $ 5.50 ​ ​ Vested ( 16 ) ​ $ 8.88 ​ ​ Forfeited ​ ( 1 ) ​ $ 5.62 ​ ​ Nonvested at end of period 74 ​ $ 6.80 ​ 1.69 ​ ​ ​ ​ ​ ​ ​ ​ ​ 1) Weighted Average Contractual Life calculation excludes the number of director RSUs that vest upon one of four performance events (refer to discussion above for details). 14 Table of Contents A summary of the Company’s RSU compensation expense is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Three Months Ended ​ ​ March 31, ( in thousands, except per share data ) ​ 2026 ​ ​ ​ 2025 Share-based compensation expense ​ $ 34 $ 32 ​ Weighted average value per share ​ $ 7.52 $ 8.90 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock Awards ​ The Company awards employees stock in lieu of cash payment for compensation, typically to satisfy accrued bonus compensation and for ad-hoc bonuses for exemplary performance. These awards are granted pursuant to the 2021 Plan. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Three Months Ended ​ ​ March 31, ​ ​ 2026 ​ 2025 ( in thousands, except per share data ) ​ Number of Shares ​ ​ ​ Fair Value ​ Weighted Average per Share ​ Number of Shares ​ ​ ​ Fair Value ​ Weighted Average per Share Fair value of stock payments in accrued compensation ​ 36 ​ $ 203 ​ $ 5.60 ​ 33 ​ $ 279 ​ $ 8.57 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consultant Stock Plan ​ The Company’s 2013 Consultant Stock Plan (the “Consultant Plan”) provides for the granting of shares of common stock to consultants who provide services related to capital raising, investor relations, and making a market in or promoting the Company’s securities. The Company’s officers, employees, and Board members are not entitled to receive grants from the Consultant Plan. The Compensation Committee is authorized to administer the Consultant Plan and establish the grant terms. The Consultant Plan provides for quarterly increases in the available number of authorized shares equal to the lesser of 1 % of any new shares issued by the Company during the quarter immediately prior to the adjustment date or such lesser amount as the Board shall determine. ​ The Consultant Plan activity is as follows: ​ ​ ​ ​ ​ ​ ​ March 31, ( in thousands ) ​ ​ ​ 2026 Reserved but unissued shares at beginning of period ​ ​ 19 Increases in the number of authorized shares ​ ​ 1 Grants ​ ​ — Reserved but unissued shares at end of period ​ 20 ​ ​ ​ ​ ​ The Consultant Plan compensation expense is summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Three Months Ended ​ ​ March 31, ( in thousands, except per share data ) ​ ​ ​ 2026 ​ ​ ​ 2025 Share-based compensation expense ​ $ 3 ​ $ 4 Weighted average value per share ​ $ 8.59 ​ $ 9.40 ​ ​ ​ ​ ​ ​ ​ ​ ​ 15 Table of Contents ​ ​ ​ Note 9 – Net Loss per Common Share The Company calculates net loss per common stock in accordance with ASC Topic 260, Earnings Per Share (“ASC 260”). Basic and diluted net loss per common stock was determined by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Under ASC 260, shares issuable for little or no cash consideration are considered outstanding common stock and included in the computation of basic net loss per share. As such, for the three months ended March 31, 2026 and 2025, the Company included its outstanding pre-funded warrants in its computation of net loss per share. The pre-funded warrants are each exercisable into one share of common stock at an exercise price of $ 0.001 per share. ​ The following potentially dilutive securities have not been included in the computation of diluted net loss per share for the three months ended March 31, 2026 and 2025, as the result would be anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ March 31, ( in thousands ) ​ 2026 ​ 2025 Stock options ​ 278 ​ 289 Restricted stock units ​ 74 ​ 99 Warrants ​ 2,128 ​ 2,127 Total shares excluded from calculation ​ 2,480 ​ 2,515 ​ ​ N ote 10 – Commitments and Contingencies Litigation From time to time the Company may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties and an adverse result in any such matter may harm the Company’s business. As of the date of this report, the Company is not a party to any material pending legal proceedings or claims that the Company believes will have a material adverse effect on the business, financial condition or operating results. On January 16, 2026, Judith Schrecker, David Maley, and Catharine M. de Lacy (collectively, the “Former Directors”), filed a petition for advancement (case number 2026-0082-CDW) in the Delaware court of Chancery for an advancement of legal fees relating to a request, by us, for the Former Directors to return material generated by a dissolved special committee formed by the Board on February 10, 2025 (“Special Committee”), which was subsequently dissolved following our 2025 annual meeting of stockholders. The advancement proceeding effectuated an advancement of monies to the Former Directors counsel for monies incurred to represent the Former Directors in this matter. The advancement proceeding followed a prescribed court process where the legal fees were reviewed to determine a reasonable amount payable to the Former Directors’ counsel for representation in this matter. We do not believe this advancement claim will have a material adverse effect on the future operations of the Company, and we do not anticipate any additional claims for advancement of legal fees in this case in the future. The total advancement claim amounted to $ 319 thousand, of which $ 180 thousand was accrued during the three months ended December 31, 2025. We delivered the full amount of the advancement claim to their legal counsel during the three months ended March 31, 2026. Indemnification Agreements The Company maintains indemnification agreements with our directors and officers that may require the Company to indemnify these individuals against liabilities that arise by reason of their status or service as directors or officers, except as prohibited by law. ​ 16 Table of Contents Note 11 – Government Assistance ​ During 2022, the Company was awarded a research grant from the Department of Energy (“DOE”) for approximately $ 250 thousand with the completion of such grant occurring in March 2023. The purpose of the grant was to produce a research paper for a flexible fuel ultra-low NOx process burner capable of burning 100% hydrogen fuel. During 2023, the Company was awarded a Phase 2 grant from the DOE to continue developing this ultra-low NOx hydrogen burner. The Phase 2 grant amount totaled approximately $ 1.6 million over a two-year period. During the three months ended March 31, 2026, we received a deadline extension from the DOE allowing us to continue work until May 27, 2026. These awards allow the Company to request reimbursements for expenditures such as labor, material, and administrative costs. During the three months ended March 31, 2026 and 2025, the Company recognized $ 28 thousand and $ 48 thousand in reimbursements from the DOE, respectively. ​ Note 12 – Subsequent Events The Company has evaluated subsequent events as of the date of this report and has none to report. ​ 17 Table of Contents SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS AND OTHER INFORMATION CONTAINED IN THIS REPORT This Quarterly Report on Form 10-Q (this “Form 10-Q” or “report”) contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and the provisions of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Forward-looking statements give our current expectations or forecasts of future events. You can identify these statements by the fact that they do not relate strictly to historical or current facts. You can find many (but not all) of these statements by looking for words such as “approximates,” “believes,” “hopes,” “expects,” “anticipates,” “estimates,” “projects,” “intends,” “plans,” “would,” “should,” “could,” “may,” “will” or other similar expressions in this report. In particular, these include statements relating to future actions; prospective products, applications, customers, and technologies; future performance or results of any products; anticipated expenses; and future financial results. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from our historical experience and our present expectations or projections. Factors that could cause actual results to differ materially from those discussed in the forward-looking statements include, but are not limited to: ● our limited cash, history of losses, and our expectation that we will continue to experience operating losses and negative cash flows in the near future; ● our ability to successfully develop and implement our technologies and achieve profitability; ● changes in government regulations that could substantially reduce, or even eliminate, the need for our technology; ● emerging competition and rapidly advancing technology in our industry that may outpace our technology; ● customer demand for the products and services we develop; ● the impact of competitive or alternative products, technologies, and pricing; ● our ability to manufacture any products we design; ● general economic conditions and events and the impact they may have on us and our potential customers; ● the impact of global supply-chain constraints and the threat of, or implementation of, tariffs on imported or exported goods and materials may adversely affect our commercialization efforts and business operations; ● our revenue has been highly concentrated among a small number or customers, and our results of operations could be harmed if we lose a key revenue source and fail to replace it; ● the impact of a cybersecurity incident or other technology disruption; ● our ability to protect our intellectual property; ● our ability to obtain adequate financing in the future; ● lawsuits and other claims by third parties or investigations by various regulatory agencies that we may be subjected to; ● our ability to retain and hire personnel with the experience and talent to develop our products and business; ● our success at managing the risks involved in the foregoing items; and ● other factors discussed in this report and in the section titled “Risk Factors” in our most recent Annual Report on Form 10-K. Forward-looking statements may appear throughout this report, including, without limitation, Item 2 “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The forward-looking statements are based upon management’s beliefs and assumptions and are made as of the date of this report. We undertake no obligation to publicly update or revise any forward-looking statements included in this report. You should not place undue reliance on these forward-looking statements. 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. ​ Note Regarding Reverse Stock Split ​ We effected a reverse stock split of our outstanding common stock at a ratio of 1-for-10, effective as of March 16, 2026, for the purpose of complying with Nasdaq Listing Rule 5550(a)(2). We have reflected the reverse stock split herein, unless otherwise indicated. 18 Table of Contents ​