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 2023-12-31

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 2024-04-24

 UNITED STATES

 SECURITIES AND EXCHANGE COMMISSION

 Washington, D.C. 20549

 FORM 10-K/A

 (Amendment No. 1)

 (Mark One)

 x

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

 For the fiscal year ended December 31, 2023

 OR

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

 For the transition period from ______________
to _______________

 Commission file number 001-35521

 CLEARSIGN TECHNOLOGIES CORPORATION

 (Exact name of registrant as specified in its
charter)

 Delaware

 (State
or other jurisdiction of
 incorporation or organization)

 26-2056298

 (I.R.S. Employer

 Identification No.)

 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:

 Title
 of each class

 Trading
 Symbol(s)

 Name
 of each exchange on

 which registered

 Common Stock

 CLIR

 The Nasdaq Stock Market
 LLC

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

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

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.

 Large accelerated filer

 Accelerated filer

 Non-accelerated filer x

 Smaller reporting company x

 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.

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.

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, 2023, 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 $ 40,360,983.

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

 As of April 24, 2024, the registrant has 45,913,546 shares of
common stock, par value $0.0001, issued and outstanding.

 DOCUMENTS INCORPORATED BY REFERENCE

 None.

 Auditor name

 BPM CPA LLP

 Location

 Santa Monica, CA

 Auditor Firm ID

 PCAOB: ID 207

 Technologies Corporation

 EXPLANATORY NOTE

 ITEM 10: DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE

 ITEM 11: EXECUTIVE COMPENSATION

 ITEM 12: SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT AND RELATED STOCKHOLDER MATTERS

 ITEM 13: CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTOR INDEPENDENCE

 ITEM 14: PRINCIPAL ACCOUNTING FEES AND SERVICES

 ITEM 15: EXHIBITS, CONSOLIDATED FINANCIAL STATEMENT SCHEDULES

 ITEM 16: FORM 10-K SUMMARY

 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, 2023 of ClearSign Technologies
Corporation (the "Company"), filed with the Securities and Exchange Commission (the "SEC") on April 1, 2024
(the "Original Form 10-K"). The purpose of this Amendment is to amend Part III, Items 10 through 14 of the
Original Form 10-K to include information previously omitted from the Original Form 10-K in reliance on General Instruction
G(3) to Form 10-K which permits the above-referenced Items to be incorporated in the Annual Report on Form 10-K by reference
from a definitive proxy statement, if such proxy statement is filed no later than 120 days after December 31, 2023. At this time,
the Company is filing this Amendment to include Part III information in our Annual Report on Form 10-K because we do not intend
to file a definitive proxy statement within 120 days of December 31, 2023. Accordingly, Part III of the Original Form 10-K
is hereby amended and restated as set forth herein. The information included herein as required by Part III, Items 10 through
14 of Form 10-K is more limited than what is required to be included in the definitive proxy statement to be filed in connection
with our annual meeting of stockholders. Accordingly, the definitive proxy statement to be filed at a later date will include additional
information related to the topics herein and additional information not required by Part III, Items 10 through 14 of Form 10-K.
The reference on the cover page of the Original Form 10-K to the incorporation by reference of our definitive proxy statement
into Part III of the Original Form 10-K is hereby deleted.

 This Amendment is also being filed with the SEC
to correct the certifications required under Sections 302 (the "302 Certifications") and 906 of the Sarbanes-Oxley Act of
2002 (the "906 Certifications," and collectively, the "Certifications") filed as Exhibits 31.1, 31.2 and 32.1
to the Original Form 10-K. The Certifications that will be filed, or furnished, as applicable, with this Amendment will correct typographical
errors within each of the 302 Certifications that resulted in such exhibits inadvertently referring to an incorrect date under each 302
Certification, and, incorrectly identifying the Annual Report on Form 10-K, the subject of the 906 Certification, as being for the
year ended December 31, 2022. Additionally, the Company is filing this Amendment to correct the hyperlinks in Exhibits 3.1 and 3.2,
as filed under Item 15 of the Original Form 10-K, and to add Exhibit 10.18, which was inadvertently not included under Item 15 of
the Original Form 10-K, both of which were the result of an inadvertent administrative error. Accordingly, the Company is filing as exhibits
to this Amendment the Certifications with correct dates and references, as well as updated Exhibits 3.1 and 3.2 under Item 15 with correct
hyperlinks.

 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.

 ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE.

 Governance of the Company

 The following table sets forth the names and ages
of the directors and executive officers serving as of the date hereof. Our officers are appointed by, and serve at the pleasure of, the
Board.

 Name

 Age

 Position

 Colin James Deller

 Chief Executive Officer and Director

 Chief Financial Officer

 Robert T. Hoffman Sr.

 Director and Chairperson of the Board

 Judith S. Schrecker

 Director and Lead Independent Director

 Catharine M. de Lacy

 Director

 David M. Maley

 Director

 Our business, property and affairs are managed
by, or under the direction of, our board of directors (the "Board"), in accordance with the General Corporation Law of the
State of Delaware ("DGCL") and our bylaws (the "Bylaws"). Members of the Board are kept informed of our business
through discussions with the Chief Executive Officer, Chief Financial Officer and other key members of management, by reviewing materials
provided to them by management, and by participating in meetings of the Board and its committees.

 Stockholders may communicate with the members of the Board, either
individually or collectively, or with any independent directors, individually or as a group, by writing to the Board at 8023 East 63 rd
Place Suite 101, Tulsa, Oklahoma 74133. These communications will be reviewed by the Company's Secretary who, depending on
the subject matter, will (i) forward the communication to the director or directors to whom it is addressed or who is responsible
for the topic matter, (ii) attempt to address the inquiry directly (for example, where it is a request for publicly available information
or a stock related matter that does not require the attention of a director), or (iii) not forward the communication if it is primarily
commercial in nature or if it relates to an improper or irrelevant topic. At each meeting of the Nominating and Corporate Governance Committee
(the "Governance Committee"), the Company's Secretary presents a summary of communications received, if any, and will
make those communications available to any director upon request.

 Colin James Deller

 Dr. Deller joined us as our President in February 2019,
transitioned to the office of Chief Executive Officer on April 1, 2019 and was appointed as a director on February 13, 2020.
Dr. Deller began his career at Hamworthy Combustion while also completing his Ph. D. In 1996, Dr. Deller joined Callidus, where
he was employed in Project Engineering and Sales, and over the course of ten years advanced to serve as Chief Combustion Engineer
and Manager of Burner Order Execution before being promoted to oversee Callidus' entire burner business. From 2010 until he left
Callidus, following the acquisition of Callidus by Honeywell, Dr. Deller served as General Manager with full profit and loss accountability
for the Honeywell UOP Callidus burner business worldwide. During that time, he led his team in developing new international markets, including
developing a leading market position in China. From May 2018 until he joined the Company, Dr. Deller served as the interim Global
Operations Director for the entire Honeywell International UOP Callidus business, which includes flares and thermal oxidizers in addition
to burners. Dr. Deller has a Bachelor of Engineering in mechanical engineering from Portsmouth Polytechnic, U.K., a doctorate in
flame chemistry from the University of Portsmouth, U.K., and an M.B.A. from The University of London.

 Mr. Hinds was appointed
as our Vice President of Finance, Controller, Treasurer, principal financial officer, and principal accounting officer on October 18,
2021. Mr. Hinds was promoted to Chief Financial Officer effective August 8, 2023. Prior to joining the Company, from July 2014
to September 2021, Mr. Hinds was employed by Enovation Controls, Inc. ("Enovation Controls"). Enovation Controls
is a stand-alone subsidiary of Helios Technologies (NASDAQ: HLIO), focused on global sales, manufacturing, and application engineering
operations, working directly with original equipment manufacturers. Mr. Hinds successively held the positions of Assistant Controller,
Controller and Vice President of Finance. In his capacity, Mr. Hinds was responsible for overseeing accounting and finance department
activities to ensure accuracy and timely dissemination of reports, including income statement, balance sheet, and cash flow. Prior to
joining Enovation Controls, Mr. Hinds worked for Stinnett & Associates, LLC, a professional advisory firm for public and
private companies, where he established risk-based audit programs to determine the adequacy and effectiveness internal control environments.
Additionally, Mr. Hinds served as a compliance analyst at Baker Hughes Company. Mr. Hinds earned his Bachelor of Science in
Accounting from Oklahoma State University and is a certified public accountant.

 Robert T. Hoffman Sr.

 Mr. Hoffman became a director of our Company
in July 2018 in conjunction with the execution of a Voting Agreement between the Company and clirSPV LLC and was appointed as Chairman
in November 2018. Mr. Hoffman served as the interim Chief Executive Officer for ClearSign between January 1, 2019, and
April 1, 2019, prior to Dr. Deller's appointment. Mr. Hoffman has more than 30 years of relevant capital markets
experience and expertise. In 2011, Mr. Hoffman founded and continues to manage Princeton Opportunity Management LLC. Previously,
he served as founder and managing partner of Candlewood Capital Management. The firm's Candlewood Funds were a family of domestic
and off-shore long/short funds, which totaled more than $1 billion in primarily institutional assets. Mr. Hoffman also was a Managing
Director and Portfolio Manager for the Growth & Income (G&I) mutual fund and institutional assets of what was originally
Scudder Stevens and Clark, where he was responsible for all buy and sell decisions. During his tenure, G&I assets under management
expanded from approximately $1.75 billion to more than $25 billion. Mr. Hoffman was also nominated by two separate governors to serve
three terms as a Member and Chairman of the State of New Jersey Investment Council (SIC) from 1990 to 2002. The SIC has ultimate oversight
responsibility for state and local pension funds totaling more than $80 billion. Mr. Hoffman's career also includes service
as the Assistant State Treasurer for Pensions and Investments for the State of New Jersey; Special Assistant to the Governor of New Jersey;
and Mergers, and Acquisitions Analyst at ABN/LaSalle Bank. He holds an M.B.A. with Distinction from the Kellogg Graduate School of Management
at Northwestern University and an Economics degree from Dartmouth College.

 Judith S. Schrecker

 Ms. Schrecker became a director of our Company
in February 2021. Ms. Schrecker brings more than 40 years of financial and operating leadership and board participation
with broad international experience. Most recently Ms. Schrecker was VP of Finance of Flat Rolled Products at ATI – Allegheny
Technologies, Inc., a Global manufacturer of technically advanced specialty materials and complex components, overseeing revenues
of over $1 billion. Prior to that Ms. Schrecker was Chief Financial Officer of Alcoa's Global Rolled Products business
and a member of the executive council of the company. Under her leadership, the Global Rolled Products business achieved historically
high profitability. Ms. Schrecker previously served on the boards of Finacity Corporation and Dress for Success Worldwide. She attended
the University of Pittsburg Graduate School of Public and International Affairs along with a B.A. in History, Economics, and Latin American
Studies from Temple University. Additionally, Ms. Schrecker is a 2020 Exceptional Women Awardees Foundation (EWA) recipient.

 Catharine M. de Lacy

 Ms. de Lacy became
a director of our Company in February 2023. She is a widely recognized expert in
ESG/Sustainability initiatives, public affairs, corporate governance, and risk management. Ms. de Lacy has worked for both public
and privately held companies including Albemarle Corporation, the Clorox Corp., Sun Products, Cabot Corp, AlliedSignal, and Occidental
Petroleum Corp. Ms. de Lacy is the co-founder and Managing Director of Riar Associates, LLC, a management consultancy where she continues
to work as a business advisor and subject matter expert on climate, sustainability, business strategy, public policy and advocacy, communications,
and risk management matters for public and private companies. She is a former board member of TORC Oil & Gas, Ltd. (TSX:TOG)
and the Environmental Law Institute's Leadership Council, and is currently serving as a board member of privately-held NTES LLC,
which provides strategic, financial, and operations management expertise in evolving energy markets and real estate investment;
the Executive Advisory Council of the Responsible Battery Coalition; and U.S.A Bobsled/Skeleton Foundation. She holds a Board Certificate
in ESG from UC Berkeley's Law School, is a Certified Director through the Harvard Business School,
and is a Qualified Risk Director and holds a certificate in Cyber Risk Governance. Ms. de Lacy received a B.A. from Merrimack
College, and an M.S. from Tufts University.

 David M. Maley

 Mr. Maley
became a director of our Company in April 2024. Mr. Maley brings forty years of broad investment experience with more than half
of that period focused on micro-cap equity research and portfolio management. Mr. Maley currently serves as the Chief Investment
Officer and Chief Compliance Officer of 1102 Partners, LLC, a family office, and investment advisory firm founded by Mr. Maley in
2021. Prior to his current role, Mr. Maley served as a Senior Vice President at Ariel Investments, where he was Lead Portfolio Manager
for the Ariel Micro-Cap Value Product fund and the Ariel Small-Cap Deep Value Product fund. During that time, he was named a "Micro-Cap
Superstar" in a 2014 Red Chip Review publication. Mr. Maley also took on management of the domestic trading team at Ariel Investments
and chaired the Trade Oversight Committee during his tenure at Ariel Investments. Prior to Ariel Investments, Mr. Maley founded and
ran Maple Hill Capital Management and served as a Vice President and Senior Portfolio Manager for ultra-high net worth clients at Harris
Bank. Mr. Maley began his career in institutional equity sales at Goldman Sachs. He received an M.B.A from the University of Chicago
Booth School Of Business and a B.B.A in finance from the University Of Notre Dame.

 The investment experience that Mr. Hoffman
and Mr. Maley bring to our Board includes experience in analyzing the operations of businesses, and particularly smaller capitalized companies,
to determine the likelihood of success. Ms. Schrecker has significant financial, business, operational and industrial experience.
Ms. de Lacy and Mr. Maley have significant experience in the areas of corporate governance and risk management. In addition, Ms. de Lacy
and Mr. Maley have experience in the areas of environmental policy and cybersecurity. We believe that their experience, together with
the expertise brought to our operations by Dr. Deller, will help us achieve our goals of proving commercial viability of our products,
generating interest from end users and original equipment manufacturers and licensing our technology. For these reasons, we concluded
that each of these individuals should serve as a director.

 None of our executive officers or directors have
been involved in a legal proceeding that requires disclosure pursuant to Item 401(f) of Regulation S-K promulgated under the Securities
Exchange Act of 1934, as amended (the "Exchange Act"). None of our executive officers or directors was selected as such as
a result of an arrangement or understanding between him and any other person.

 Independence of Directors

 In determining the independence of our directors,
we apply the definition of "independent director" provided under the listing rules of The Nasdaq Stock Market LLC ("Nasdaq").
On an annual basis, the Board reviews the independence of all directors under guidelines established by Nasdaq and in light of each director's
background, employment and affiliations with the Company and members of management, as well as significant holdings of Company securities.
This review considers all known relevant facts and circumstances in making an independence determination. The Board concluded its annual
review of director independence in March 2024. After considering all relevant facts and circumstances, the Board affirmatively determined
that all of the directors serving on the Board are independent within the meaning of Nasdaq Listing Rule 5605(a)(2) and Rule 10A-3(b) promulgated
under the Exchange Act, with the exception of Robert T. Hoffman, Sr. and Colin James Deller.

 Committees of our Board

 The Board has three standing committees, the Audit &
Risk Committee, the Human Capital & Compensation Committee (the "Compensation Committee") and the Governance Committee
(collectively, the "Board Committees"). All members of the Board Committees are non-employee directors who are deemed independent.

 Audit & Risk Committee

 As of the date of this report, the Audit &
Risk Committee was comprised of Judith Schrecker (Chairperson), Catharine M. de Lacy and David M. Maley. Each
member of the Audit & Risk Committee is financially literate and our Board has determined that Judith Schrecker qualifies as an "audit
committee financial expert" as defined in applicable SEC rules. The role of the Audit & Risk Committee includes,
but is not limited to, the following:

 overseeing management's preparation of our financial statements and management's conduct of the accounting and financial
reporting processes;

 appointing, compensating, retaining, and overseeing the work of the independent registered public accounting firm engaged for the
purpose of preparing or issuing an audit report or performing other audit, review or attest services for the Company;

 overseeing management's maintenance of internal controls and procedures for financial reporting at least annually;

 overseeing risks related to cybersecurity, including the security of corporate information and the steps management takes to monitor
and control cybersecurity risks;

 overseeing our compliance with applicable legal and regulatory requirements, including without limitation, those requirements relating
to financial controls and reporting;

 overseeing the independent registered public accounting firm's qualifications and independence;

 preparing the report required by the rules of the Securities and Exchange Commission to be included in our proxy statement; and

 discharging such duties and responsibilities as may be required of the Audit & Risk Committee by the provisions of applicable
laws, rules or regulations.

 The Audit & Risk Committee is authorized
(without seeking Board approval) to retain or terminate special legal, accounting or other advisors and may request any officer or employee
of the Company or the Company's outside counsel or independent registered public accounting firm to meet with any members of, or
advisors to, the Audit & Risk Committee.

 A copy of the charter of the Audit & Risk
Committee is available on our website at www.clearsign.com (under "Investors - Corporate Governance").

 Human Capital & Compensation Committee

 As of the date of this report, the Compensation
Committee was comprised of Judith Schrecker (Chairperson) and Catharine M. de Lacy. The role of the Compensation Committee is to:

 review, approve, and recommend to the Board our compensation and benefit s policies generally and
the annual compensation (base salary, bonus and other benefits) for all of our executives, including our Chief Executive Officer;

 administer the ClearSign Technologies Corporation 2021 Equity Incentive
Plan (the "2021 Plan"), the 2013 Consultant Stock Plan and the ClearSign Technologies Corporation 2011 Equity Incentive Plan;
and

 annually review and make recommendations to the Board with respect to the compensation of non-executive directors,
 including any incentive plan compensation.

 A copy of the charter of the Compensation Committee
is available on our website at www.clearsign.com (under "Investors-Corporate Governance").

 The Compensation Committee may engage outside advisers,
including outside auditors, attorneys, and consultants, as it deems necessary to discharge its responsibilities. The Compensation Committee
has sole authority to retain and terminate any compensation expert or consultant used to provide advice on compensation levels or assist
in the evaluation of director, Chief Executive Officer or senior executive compensation, including sole authority to approve the fees
of any expert or consultant and other retention terms. In addition, the Compensation Committee considers, but is not bound by, the recommendations
of our Chief Executive Officer with respect to the compensation packages of our other executive officers.

 Pursuant to the terms of the 2021 Plan, the Compensation
Committee may delegate to one or more officers of the Company the authority to grant awards under the plan to participants who are not
insiders of the Company.

 Nominating and Corporate Governance Committee

 As of the date of this report, the Governance Committee
was comprised of Catharine M. de Lacy (Chairperson) and Judith Schrecker. The role of the Governance Committee is to:

 evaluate from time to time the appropriate size (number of members) of the Board and recommend any increase or decrease;

 determine the desired skills and attributes of members of the Board, taking into account the needs of the business and listing standards;

 establish criteria for prospective members, conduct candidate searches, interview prospective candidates, and oversee programs to
introduce the candidate to us, our management, and operations;

 review planning for succession to the position of Chief Executive Officer and other senior management positions;

 annually recommend to the Board persons to be nominated for election as directors;

 annually recommend to the Board the members and leadership of all standing committees, as well as leadership of the Board and to fill
vacancies as needed;

 adopt or develop for Board consideration corporate governance principles and policies; and

 periodically review and report to the Board on the effectiveness of corporate governance procedures and the Board as a governing body,
including conducting an annual self-assessment of the Board and its standing committees.

 A copy of the charter of the Governance Committee
is available on our website at www.clearsign.com (under "Investors - Corporate Governance").

 Director Qualifications and Diversity

 The Board seeks independent directors who represent
a diversity of backgrounds, ages and experiences that will enhance the quality of the Board's deliberations and decisions. Candidates
should preferably have board experience with one or more companies or should have achieved a high level of distinction in their chosen
fields. The Board is particularly interested in maintaining a mix that includes individuals who are active or retired executive officers
and senior executives, particularly those with experience in combustion, technology, air pollution control and air emission regulation,
intellectual property, start-up companies, research and development, strategic planning, business development, upstream, midstream and
downstream oil and gas, energy, finance, accounting and banking, as well as impact investing and environmental, social and governance
investing, reporting and/or compliance.

 In evaluating nominations to the Board, the Governance
Committee also looks for certain personal attributes, such as integrity, ability and willingness to apply sound and independent business
judgment, comprehensive understanding of a director's role as a fiduciary to stockholders and with respect to corporate governance,
availability for meetings and consultation on Company matters, and the willingness to assume and carry out such fiduciary responsibilities.

 Risk Oversight by the Board of Directors

 It is the management's responsibility to
assess and manage the various risks we face. It is the Board's responsibility to oversee management in this effort, in order to
ensure that risks and uncertainties that may relate to our ongoing operations and to our plans for the future are considered and sought
to be managed appropriately. In exercising its oversight, the Board has allocated some areas of focus to the Board Committees and has
retained areas of focus for itself, as more fully described below.

 Full
Board. Risks and exposures focused on by the full Board include risk management as a whole as well as strategic, financial
and execution risks including safety risks, risks associated with intellectual property, and other current matters that may present material
risk to our operations, plans, prospects or reputation. Throughout the year, the Chief Executive Officer discusses these risks with
the Board during strategy reviews that focus on a particular function or aspect of our business.

 Audit &
Risk Committee. Risks and exposures focused on by the Audit & Risk Committee are those associated with financial
matters, particularly financial reporting, tax, accounting, disclosure, internal control over financial reporting, cyber, the Foreign
Corrupt Practices Act, financial policies, investment guidelines, and credit and liquidity matters.

 Governance
Committee. Risks and exposures focused on by the Governance Committee are those relating to corporate governance and management
and director succession planning.

 Compensation
Committee. Risks and exposures focused on by the Compensation Committee are those associated with leadership assessment
and compensation programs and arrangements, including incentive plans, to ensure that compensation incentives are aligned with our risk
management objectives.

 Board Leadership Structure

 The Chairperson of the Board, if appointed pursuant
to Section 6.1 of the Bylaws, presides at all meetings of the Board and the annual meeting of stockholders. Mr. Hoffman was
appointed as Chairperson of the Board at a special meeting of the Board held on November 6, 2018, at which time the Board determined
to separate the offices of the Chief Executive Officer and the Chairperson. At that time, the Board believed such a leadership structure
would increase the Board's independence from management. Ms. Schrecker is currently serving as our lead independent director.

 The responsibilities of our
lead independent director include:

 to act as a liaison between the independent and non-independent directors;

 to develop, maintain and revise the annual Board calendar;

 to preside over all Board meetings at which the Chairperson of the Board is not present; and

 other duties as may be assigned to the lead independent director by the Board.

 A determination regarding the designation and appointment
of a Board Chairperson and/or lead independent director will be made each year following the Company's annual meeting of stockholders.

 Compensation Committee Interlocks and Insider Participation

 None of our prior or current executive officers
serves as a member of the Board or Compensation Committee of any entity that has one or more executive officers serving as a member of
our Board or the Compensation Committee.

 Code of Ethics

 We adopted a Code of Business Conduct and Ethics
("Code of Ethics") applicable to our principal executive officer and principal financial and accounting officer and any persons
performing similar functions, as well as to our employees, officers, directors, agents and representatives. The Code of Ethics requires,
among other things, that all of the foregoing people avoid conflicts of interest, comply with all laws and other legal requirements, conduct
business in an honest and ethical manner, and otherwise act with integrity and in our best interest. The Code of Ethics is available on
our website at www.clearsign.com (under "Investors-Corporate Governance"). We will promptly disclose any amendment to, or
a waiver from, a provision of our Code of Ethics that applies to members of our board of directors, our principal executive officer, principal
financial officer, principal accounting officer or controller, or persons performing similar functions by posting the information on our
Internet website, www.clearsign.com.

 Employee, Officer, and Director Hedging

 Our policy against insider trading prohibits all
employees and directors from engaging in any short sales of our securities, hold our securities in a margin account, or pledge our securities
as collateral for a loan.

 Family Relationships

 There are no family relationships
among any of our executive officers or directors.

 ITEM 11. EXECUTIVE COMPENSATION.

 Executive Officers Compensation

 The table below summarizes the total compensation
paid to or earned by our Chief Executive Officer and Chief Financial Officer in the years ended December 31, 2023 and 2022, in accordance
with Item 402(m)(2) of Regulation S-K. These officers are referred to herein as the "named executive officers" or
"NEOs." The amounts represented in the "Option Awards" column reflects the stock compensation expense recorded
by the Company pursuant to ASC Topic 718 and does not necessarily equate to the income that will ultimately be realized by the named executive
officers for such awards.

 Summary Compensation Table

 Option

 Restricted Stock

 All Other

 Name and Principal

 Salary

 Bonus

 Awards (1)

 Awards (2)

 Compensation (3)

 Total

 Position

 Year

 ($)

 ($)

 ($)

 ($)

 ($)

 ($)

 Colin J. Deller

 2023

 350,000

 138,989
 (4)

 115,192
 (6)

 —

 38,320

 642,501

 Chief Executive Officer

 2022

 350,000

 86,747
 (5)

 26,238
 (6)

 —

 35,220

 498,205

 2023

 200,000

 47,780
 (4)

 31,155
 (7)

 7,285
 (9)

 33,637

 319,857

 Chief Financial Officer

 2022

 200,000

 46,717
 (5)

 52,410
 (8)

 —

 30,720

 329,847

 (1)
 The amounts included in this column are the aggregate dollar amounts of compensation expense recognized by us for financial statement
reporting purposes in accordance with Accounting Standards Codification 718, Compensation-Stock Compensation, and includes amounts from
option awards granted in 2021, 2020 and 2019. For information on the valuation assumptions used in calculating these dollar amounts, see
Notes 2 and 8 to our consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2023.
These amounts reflect our accounting expense for these awards and do not correspond to the actual value that may be recognized by the
individuals upon option exercise.

 (2)
 The amounts included in this column are the aggregate dollar amounts of compensation expense recognized by us for financial statement
reporting purposes in accordance with Accounting Standards Codification 718, Compensation-Stock Compensation, and includes amounts from
restricted stock awards granted. For information on the valuation assumptions used in calculating these dollar amounts, see Notes 2 and
8 to our consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2023. These amounts
reflect our accounting expense for these awards and do not reflect the actual economic value that may be realized by the individuals upon
vesting of such awards.

 (3)
 Relates to healthcare benefits and employer matching in a defined contribution retirement plan available to all employees.

 (4)
 Bonuses for 2023 were accrued in 2023 and paid in stock during the first quarter of 2024.

 (5)
 Bonuses for 2022 were accrued in 2022 and paid in stock during the first quarter of 2023.

 (6)
 Relates to performance based stock option awards from our 2011 Equity Incentive Plan, granted to Dr. Deller in 2021. These are
expensed over the performance period as performance conditions associated with the stock option are considered achieved or probable, as
determined by the Compensation Committee.

 (7)
 Relates to time based stock option awards from our 2021 Plan, granted
to Mr. Hinds in 2021. These are expensed over the service period when the service conditions associated with the stock option are
satisfied.

 (8)
 Relates to time based stock option awards from our 2021 Plan, granted
to Mr. Hinds in 2022 and 2021. These are expensed over the service period when the service conditions associated with the stock option
are satisfied.

 (9)
 Relates to time based restricted stock awards from our 2021 Plan granted
to Mr. Hinds in 2023. These are expensed over the service period when the service conditions associated with the restricted stock
award are satisfied.

 Outstanding Equity Awards

 The following table sets forth information concerning outstanding equity
awards held by our NEO's at December 31, 2023.

 Equity Incentive

 Equity Incentive

 Plan Awards:

 Plan Awards:

 Equity Incentive

 Number of Securities

 Number of Securities

 Plan Awards:

 Underlying Unexercised

 Underlying Unexercised

 Number of Restricted

 Options

 Unearned Options

 Stock Units

 (#)

 (#)

 Option Exercise

 Option Expiration

 (#)

 Name

 Exercisable

 Unexercisable

 Price ($)

 Date

 Unvested

 Colin J. Deller

 178,161
 (1)

 —

 $
 0.94

 2/14/30

 —

 200,000
 (1)

 —

 $
 2.25

 1/28/29

 —

 400,000
 (1)

 —

 $
 1.16

 1/28/29

 —

 140,000
 (2)

 450,000
 (2)

 $
 3.37

 1/10/31

 —

 100,000
 (1)

 —

 $
 1.83

 10/18/31

 30,380

 12,788
 (1)

 —

 $
 1.44

 1/6/2032

 —

 (1)
 At December 31, 2023, these options have vested 100%.

 (2)
 Unearned options vest upon completion of performance milestones as
outlined in the option award agreement. The Board regularly monitors performance milestones to determine option vesting eligibility.

 Employment Contracts and Termination of Employment and Change-in-Control
Arrangements

 Employment Agreement with Colin James Deller

 On January 28, 2019 (the "Effective
Date"), the Company and Colin James Deller entered into an employment agreement pursuant to which the Company employed Dr. Deller
as its President until April 1, 2019, at which time Dr. Deller became the Company's Chief Executive Officer. Pursuant
to the agreement, the Company pays Dr. Deller an annual salary of $350,000. As an inducement to accept employment with the Company,
Dr. Deller was also granted an option to purchase 400,000 shares of the Company's common stock at an exercise price of $1.16
per share and an option to purchase 200,000 shares of the Company's common stock at an exercise price of $2.25 per share. Each option
has a term of 10 years and has vested as follows: one-third of the options vested on the Effective Date; one-third of the options
vested on the first anniversary of the grant date; and one-third of the options vested on the second anniversary of the grant date. Dr. Deller
is also eligible to participate in such healthcare and other benefit programs made available to employees of the Company. Dr. Deller is
eligible for annual bonuses with a value of up to 60% of his annual salary. Dr. Deller and the Compensation Committee meet annually to
establish (i) performance standards and goals ("Standards and Goals") to be met by him and (ii) bonus targets based on the
Standards and Goals that are achieved. Any bonuses will be paid at the Compensation Committee's discretion in cash and/or via equity
awards made under our 2021 Plan, or any successor plan thereto, of the type of equity award as authorized by the Compensation Committee,
which may include options to purchase Company's common stock to be valued using the Black-Scholes option valuation model, and/or
common stock, restricted stock, restricted stock units, performance stock or performance stock units. If Dr. Deller is terminated without
cause, if he resigns for any reason, dies, or becomes disabled, he is entitled to certain severance benefits. Dr. Deller may voluntarily
resign for any reason by providing us with 30 days' prior notice. If the Company terminates Dr. Deller without cause or he is terminated
within 12 months of a change in control, then Dr. Deller will be entitled to severance benefits, including 12 months of his annual salary.

 Offer Letter with Brent Hinds

 Brent Hinds received an offer letter from the Company,
dated as of September 30, 2021 and effective as of October 18, 2021 (the "Offer Letter"), setting forth the terms
of his employment and compensation arrangement, which he accepted. Pursuant to the Offer Letter, Mr. Hinds is paid an annual base
salary of $200,000 in addition to equity compensation and other benefits set forth in the Offer Letter. Mr. Hinds is eligible for annual
bonuses with a value up to 40% of his annual salary, and comprised of long- and short-term incentives awards.

 Mr. Hinds is also eligible to participate
in such healthcare and other benefit programs made available to employees of the Company. His employment has no specified term and is
on an at-will basis.

 On
August 8, 2023, we promoted Mr. Hinds to Chief Financial Officer of the Company. In connection with the promotion, the Company
amended the Offer Letter to provide for severance payments in certain instances (the "Amendment"). Specifically, the Amendment
provides for severance payments in an amount equal to one (1) year salary plus any accrued but unpaid salary, vacation, and bonus
amounts upon termination of Mr. Hinds' employment without "Cause" or upon a "Change in Control," as
such terms are defined in the Amendment. Additionally, if Mr. Hinds' employment is terminated for Cause, he will not be eligible
for any severance payments. No other changes were made to the Offer Letter.

 Change of Control Arrangements

 All of the option awards and stock awards granted
to the Company's executive officers pursuant to the 2021 Plan include change-in-control arrangements whereby, in the event that
a successor corporation does not assume or substitute the outstanding executive officers' awards, any unvested award will be fully
vested, including awards contingent on performance-based goals. Upon a change-in-control, these vested awards will be exercisable for
a period of time determined by the administrator of the 2021 Plan, and any award that becomes fully vested as a result of a change-in-control
will terminate upon expiration of such period.

 Compensation Discussion

 Overview

 The Compensation Committee administers our executive
compensation and benefit programs. The Compensation Committee is comprised exclusively of independent directors and oversees all compensation
and benefit programs and actions that affect our executive officers.

 Compensation Process and Role of Management

 The Compensation Committee is responsible for determining
and approving all compensation for our executive officers. Pursuant to its charter, the Compensation Committee reviews and approves, subject
to applicable Board ratification, the salary, annual incentive compensation or bonus, long-term incentive compensation in the form of
stock options, restricted stock units, or stock grants, all other employment, severance and change-in-control agreements and any other
compensation applicable to executive officers. As discussed below, our Chief Executive Officer assists the Compensation Committee in its
deliberations with respect to the compensation payable to our other executive officers.

 At the end of or immediately following each fiscal year,
our Chief Executive Officer evaluates executive officer performance for the prior fiscal year, other than his own performance, and
discusses the results of such evaluations with the Compensation Committee. The Chief Executive Officer assesses each executive officer's
performance during the year based upon subjective factors concerning such officer's individual business goals and objectives,
and the contributions made by the executive officer to our overall results. The Chief Executive Officer then makes specific recommendations
to the Compensation Committee for adjustments to base salary and the grant of a target bonus and/or equity award, if appropriate, as part
of the compensation package for each executive officer, other than himself, for the next fiscal year.

 The Compensation Committee reviews the performance
of the Chief Executive Officer and determines all compensation for the Chief Executive Officer. The Chief Executive Officer is not present
at the time the Compensation Committee reviews his performance and discusses his compensation.

 Evaluation of Compensation Practices

 In developing our director compensation program
and as basis for establishing such compensation, the Compensation Committee gathers and reviews data from the National Association of
Corporate Directors as well as for various publicly traded companies that the Compensation Committee believes to be similar to the Company
in some respect, taking into consideration market capitalization, number of employees, amount of revenue, net cash used or generated in
operations and the industries in which such companies operate. The goal is to attract qualified candidates and motivate director behavior
by adequately compensating for the time, effort, and commitment required. Establishing a transparent process that includes industry standards
and comparisons, while factoring in the unique circumstances of the Company, is critical. Compensation may be in the form of cash, options,
restricted stock units, or stock with consideration given to the Company's overall resources during any given period when making
a determination regarding the appropriate mix of each component of director compensation. As a result of such review, in 2023, each non-executive
director's annual compensation was paid in restricted stock units. Equity compensation for directors is designed to build an ownership
stake in the Company while conveying incentives relative to the returns recognized by our stockholders.

 Corporate
Incentive Program

 In order to enable us to attract, retain and reward
our employees for their superior work, and to motivate such employees to achieve our specific corporate and individual objectives, the
Compensation Committee provide incentives based upon or exceeding specified targets that are challenging but achievable.

 At the beginning of each fiscal year, the Compensation
Committee reviews and recommends to the Board the Corporate Incentive Plan (the "CIP"), which provides bonus awards to certain
employees, including our named executive officers. The annual CIP is broken into three target categories: company based goals, employee
specific goals and time based goals. Bonuses are calculated based on the Compensation Committee's determination of target achievement
and category apportionment percentages. The Compensation Committee may, from time to time, recommend changing target categories and apportionment
percentages based on their annual review of the CIP.

 Grants under the CIP are generally made in the
form of equity, including common stock and restricted stock units.

 Director Compensation

 The following table sets forth information concerning
compensation for services rendered by our non-executive directors for the year ended December 31, 2023. The amounts represented in
the "Option Awards" and "Restricted Stock Units" column reflect the grant date fair value of the options computed
in accordance with FASB ASC Topic 718 and do not necessarily equate to the income that will ultimately be realized by the director for
such awards. David M. Maley did not receive any compensation in the year ended December 31, 2023, as he was not appointed as a director
until April 2024.

 Fees

 Nonqualified

 Earned

 Restricted

 Non-Equity

 Deferred

 or Paid in

 Stock

 Option

 Incentive Plan

 Compensation

 All Other

 Name

 Cash

 Units

 Awards

 Compensation

 Earnings

 Compensation

 Total

 Robert T. Hoffman, Sr.

 (1)

 $
 —

 $
 79,997

 $
 —

 $
 —

 $
 —

 $
 —

 $

 79,997

 Judith S. Schrecker

 (2)

 —

 99,623

 —

 —

 —

 —

 99,623

 Gary DiElsi

 (3)

 —

 72,373

 —

 —

 —

 —

 72,373

 Susanne L. Meline

 (4)

 —

 23,000

 —

 —

 —

 —

 23,000

 Catharine M. de Lacy

 (5)

 —

 64,058

 —

 —

 —

 —

 64,058

 $
 —

 $
 339,051

 $
 —

 $
 —

 $
 —

 $
 —

 $

 339,051

 (1)
 Since his appointment as a director and as of December 31, 2023, Mr. Hoffman has received grants of 13,153 shares of common
stock, 185,212 shares of restricted stock units, and options for the purchase of 186,500 shares of common stock for his services.

 (2)
 Since her appointment as a director and as of December 31, 2023, Ms. Schrecker has received 220,194 shares of restricted
stock units, and options for the purchase of 17,000 shares of common stock for her services.

 (3)
 Mr. DiElsi received 115,993 shares of restricted stock units as
compensation for his services. Mr. DiElsi resigned as a director, effective as of November 9, 2023.

 (4)
 Ms. Meline received grants of 27,027 shares of common stock, 147,578
shares of restricted stock units, and options for the purchase of 204,750 shares of common stock for her services. Ms. Meline resigned
as a director, effective February 21, 2023.

 (5)
 Since her appointment as a director and as of December 31, 2023, Ms. de Lacy has received 64,861 shares of restricted stock
units as compensation for her services.

 Director Compensation Plan

 Our
non-executive directors are entitled to an annual compensation of $60,000, except for the Chairperson of the Board, who receives an annual
compensation of $80,000, plus reimbursement for ordinary and reasonable expenses incurred in exercising their responsibilities
in accordance with the Company's expense reimbursement procedure applicable to all employees of the Company. Our lead independent
director is also entitled to receive additional annual compensation of $15,000.

 Our non-executive directors received the following
additional annual compensation for service on the Board Committee's, as applicable, during the year ended December 31, 2023:

 Committee

 Chair

 Member

 Audit & Risk Committee

 $
 19,000

 $
 7,500

 Compensation Committee

 $
 7,500

 $
 3,000

 Nominating and Corporate Governance Committee

 $
 6,500

 $
 3,000

 In the year ended December 31, 2023, each
non-executive director's annual compensation was paid in restricted stock units. This component of the Company's director
compensation program is designed to build an ownership stake in the Company while providing an incentive to directors that corresponds
with the returns recognized by our stockholders. Restricted stock unit awards to non-executive directors are anticipated to continue in
future years as a means to increase alignment of directors with the Company's stockholders.

 Other than the 2021 Plan, the independent directors
are not eligible to participate in the Company's employee benefit plans, including the retirement plan.

 ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT
AND RELATED SHAREHOLDER MATTERS.

 The following table shows information known to
us about beneficial ownership of our common stock by:

 each of our directors;

 each individual identified as a named executive officer in the section of this report titled "Executive Compensation";

 all of our directors and executive officers as a group; and

 each stockholder known by us to beneficially own 5% or more of our common stock.

 Beneficial ownership and percentage ownership
are determined in accordance with the rules of the SEC. Under these rules, beneficial ownership generally includes any shares as
to which the individual or entity has sole or shared voting power or investment power and includes any shares that an individual or entity
has the right to acquire ownership of on or before June 25, 2024, which is 60 days from the date of this report, through the
exercise of any option, warrant, conversion privilege or similar right. In computing the number of shares beneficially owned by a person
and the percentage ownership of that person, shares of our common stock that could be issued upon the exercise of outstanding options,
restricted stock units, and warrants that are exercisable on or before June 25, 2024 are considered to be outstanding. These shares,
however, are not considered outstanding as of the Record Date when computing the percentage ownership of each other person.

 To our knowledge, except as indicated in the footnotes
to the following table and subject to state community property laws where applicable, all beneficial owners named in this table have sole
voting and investment power with respect to all shares shown as beneficially owned by them. Applicable percentage of ownership is
based on 45,913,546 shares of our common stock outstanding as of April 24, 2024.

 Amount of

 Beneficial

 Ownership

 Percent

 Name and Address of Beneficial Owner (1)

 (2)

 of Class

 Directors and Officers:

 Colin James Deller

 1,069,467

 (3)

 2.3

 %

 187,846

 (4)

 0.4

 %

 Robert T. Hoffman, Sr.

 6,500,029

 (5)

 14.2

 %

 Judith S. Schrecker

 17,000

 (6)

 —

 %

 Catharine M. de Lacy

 —

 (7)

 —

 %

 David M. Maley

 (8)

 —

 %

 All Directors and Executive Officers as a Group (6 persons)

 7,774,342

 16.9

 %

 5% Stockholders:

 clirSPV LLC

 6,189,857

 (9)

 13.5

 %

 (1)
 Except as set forth below, the address of each executive officer and director is 8023 East 63rd Place, Suite 101, Tulsa, Oklahoma 74133.

 (2)
 Beneficial ownership is determined in accordance with Rule 13d-3 under the Securities Exchange Act of 1934, as amended, and is
generally assigned to the person holding voting power and/or investment power with respect to securities. With the exception of the securities
beneficially owned by our officers and directors and their affiliates, the ownership of the shares of common stock listed above were determined
using public records. These amounts are based upon information available to the Company as of the date of this filing.

 (3)
 Includes common stock holdings of 121,306 shares and options to purchase 948,161 shares of common stock which may be exercised on
or before June 25, 2024. Excludes options to purchase 420,000 shares of common stock, none of which will vest on or before June 25,
2024.

 (4)
 Includes common stock holdings of 72,431 shares, 2,627 shares of performance restricted stock units which are anticipated to vest
before June 25, 2024, and options to purchase 112,788 shares of common stock which may be exercised on or before June 25, 2024.
Excludes 42,895 shares of restricted stock units, none of which will vest on or before June 25, 2024.

 (5)
 Includes common stock holdings of 123,672 shares and options to purchase
186,500 shares of common stock which may be exercised on or before June 25, 2024 and the shares references in footnote 9 below. Excludes
224,311 shares of restricted stock units, none of which are expected to vest on or before June 25, 2024.

 (6)
 Includes options to purchase 17,000 shares of common stock which may be exercised on or before June 25, 2024. Excludes 271,267
shares of restricted stock units, none of which are expected to vest on or before June 25, 2024.

 (7)
 Excludes 102,493 shares of restricted stock units, none of which are expected to vest on or before June 25, 2024.

 (8)
 Excludes 14,409 shares of restricted stock units, none of which are expected to vest on or before June 25, 2024.

 (9)
 Consists of 6,189,857 shares held of record by clirSPV LLC. Robert T. Hoffman Sr. is the Managing Member of GPclirSPV LLC, which is the
Manager of clirSPV LLC. Robert T. Hoffman, Sr. is the Manager of Princeton Opportunity Management LLC, which has an Investment Management
Agreement with clirSPV LLC and shares the power to vote the securities beneficially owned by clirSPV LLC. As such, each of GPclirSPV LLC,
Robert T. Hoffman, Sr. and Princeton Opportunity Management LLC may be deemed to have or share beneficial ownership of the shares of common
stock held directly by clirSPV LLC. The business address of Mr. Hoffman and the entities above is 119 Warren Avenue, 3rd Floor, Spring
Lake, New Jersey 07762.

 ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTOR
INDEPENDENCE.

 Except
as disclosed herein, no director, executive officer, stockholder holding at least 5% of shares of our common stock, or any family member
thereof, had any material interest, direct or indirect, in any transaction, or proposed transaction since January 1, 2022, in which
the amount involved in the transaction exceeds the lesser of $120,000 or one percent (1%) of the average of our total assets at the year-end
for the last two completed fiscal years.

 Investment by clirSPV LLC

 In connection with a private placement of the Company's
common stock pursuant to a Stock Purchase Agreement dated July 12, 2018, the Company granted clirSPV LLC (the "SPV")
a right to purchase certain new equity securities that the Company sells for the purpose of raising capital on terms and conditions no
different from those offered to other purchasers (the "Participation Right") so that it could maintain a 19.99% percentage
ownership (the Percentage Ownership") of the Company's outstanding common stock. The Participation Right will expire
on December 31, 2024. Further, in conjunction with this investment made by the SPV, we entered into a Voting Agreement with the SPV
pursuant to which Robert T. Hoffman, Sr. was appointed as a director on our Board.

 The purpose of the Participation Right is to allow
the SPV to keep its Percentage Ownership. In no event may the SPV exercise the Participation Right to the extent it would cause the SPV
to own 20% or more of the Company's then outstanding shares of common stock or hold shares with 20% or more of the voting power
of the Company. The Company and the SPV entered into a written waiver dated December 18, 2020, pursuant to which the SPV waived its
right to exercise the Participation Right in connection with the Company's "at-the-market" offering entered into in
December 2020. In lieu of participating in such offering, the Company and the SPV agreed that, for each sale of no less than 100,000 shares
of our common stock to a single investor (each such sale, a "Block Trade") made in such offering, the SPV may, for a period
of 20 business days following such Block Trade, purchase from the Company at the price sold to such investor in the Block Trade, unregistered
shares of our common stock up to a number of shares of common stock that will allow the SPV to maintain the Percentage Ownership.

 Additionally, because certain elements of the Participation
Right, such as the notice provisions and closing period, are not compatible with raising capital in a public offering, on May 26,
2022 (the "Waiver Date"), the SPV agreed to waive the notice requirements and other related closing mechanics for such Participation
Right (the "Waiver"). In exchange for such Waiver, we and the SPV agreed that, following the Waiver Date, the SPV may purchase
from us, at the price sold to the investors in an offering, unregistered shares of our common stock in a number that will allow it to
maintain the Percentage Ownership our outstanding common stock, provided that the SPV notifies us that it will exercise such right within
30 days following the final closing of such offering (the "Offering Response Date") and the completion of such purchase must
occur within six (6) business days of the Offering Response Date.

 Following the completion of an underwritten offering in June 2022,
on July 8, 2022, the SPV exercised its Participation Right and purchased 1,591,594 shares of unregistered common stock at $1.11 per share.

 In addition, the Company and the SPV agreed that
effective upon the Investor Holder Consent (as defined below), the Participation Right, subject to the Waiver and modification contained
therein, would be extended from December 31, 2023 to such date that the holders of two-thirds of the outstanding units of the SPV
agree (the "Investor Holder Consent") to extend such holder's existing agreement that he/she/it will have no right to
force a redemption of his/her/its interests in the SPV (the "Redemption Right"); provided, however, that the SPV provides
written notice to the Company of the Investor Holder Consent prior to December 31, 2023 and the Participation Right will in no event
extend beyond June 30, 2027. On December 30, 2023, the Company received notice from the SPV that the holders of at least two-thirds
of the outstanding units of the SPV agreed to extend the waiver of the Redemption Right until December 31, 2024. Accordingly, the
Participation Right now expires on December 31, 2024.

 Mr. Hoffman, our Chairman and
a current member of our Board, is the Managing Member of GPclirSPV LLC, which is the Manager of the SPV. Mr. Hoffman. is the Manager of
Princeton Opportunity Management LLC, which has an Investment Management Agreement with the SPV and shares the power to vote the securities
beneficially owned by the SPV. As such, each of GPclirSPV LLC, Mr. Hoffman and Princeton Opportunity Management LLC may be deemed to have
or share beneficial ownership of the shares of common stock held directly by the SPV.

 Review, Approval or Ratification
of Transactions with Related Persons

 The Board reviews issues involving potential conflicts
of interest, and reviews and approves all related party transactions, including those required to be disclosed as a "related party"
transaction under applicable federal securities laws. The Board has not adopted any specific procedures for conducting reviews of potential
conflicts of interest and considers each transaction in light of the specific facts and circumstances presented. However, to the extent
a potential related party transaction is presented to the Board, the Company expects that the Board would become fully informed regarding
the potential transaction and the interests of the related party, and would have the opportunity to deliberate outside of the presence
of the related party. The Company expects that the Board would only approve a related party transaction that was in the best interests
of, and fair to, the Company and our stockholders, and further would seek to ensure that any completed related party transaction was on
terms no less favorable to the Company than could be obtained in a transaction with an unaffiliated third party.

 Independence of Directors

 In determining the independence of our directors,
we apply the definition of "independent director" provided under Nasdaq's listing rules. On an annual basis, the Board
reviews the independence of all directors under guidelines established by Nasdaq and in light of each director's background, employment
and affiliations with the Company and members of management, as well as significant holdings of Company securities. This review considers
all known relevant facts and circumstances in making an independence determination. The Board concluded its annual review of director
independence in March 2024. After considering all relevant facts and circumstances, the Board affirmatively determined that all of
the directors serving on the Board are independent within the meaning of Nasdaq Listing Rule 5605(a)(2) and Rule 10A-3(b) promulgated
under the Exchange Act, with the exception of Robert T. Hoffman, Sr. and Colin James Deller.

 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, 2023 and 2022, respectively, and fees billed for other services
rendered by BPM during those periods.

 2023

 2022

 Audit Fees

 $
 84,500

 $
 80,500

 Tax Fees

 $
 —

 $
 14,500

 All Other Fees

 $
 40,665

 $
 52,765

 Total

 $
 125,165

 $
 147,765

 Audit
Fees. "Audit Fees" are the aggregate fees of BPM attributable to professional services rendered in 2023 and 2022
for the audit of our annual consolidated financial statements and 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.

 Tax
Fees. "Tax Fees" are billed for professional services rendered to us for tax compliance, tax advice, and tax planning.
Management, with the approval of the Audit & Risk Committee, hired Eide Bailly LLP in 2023 to perform tax preparation and advisory
services. This transition was a strategic initiative led by Management to separate tax preparation services from our independent registered
public accounting firm.

 All
Other Fees. "All Other Fees" are attributable to customary agreed upon professional services in connection with
our "at-the market" offering sales agreement executed in December 2020, filing our shelf registration statement on Form S-3
in August 2023, and review of our annual proxy statement.

 Pre-approval Policies and Procedures

 The Audit & Risk 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 2023 and 2022.

 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:

 Exhibit
 Number

 Description

 3.1**

 Certificate of Incorporation of ClearSign Technologies Corporation, a Delaware corporation. (incorporated by reference to Exhibit 3.3 to the Company's Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).

 3.2* *

 Bylaws of ClearSign Technologies Corporation, a Delaware corporation (incorporated by reference to Exhibit 3.4 to the Company's Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).

 10.18**+

 Amendment to Offer Letter between the Company and Brent Hinds, dated August 8, 2023 (incorporated by reference to the Company's
Form 10-Q filed with the Securities and Exchange Commission on August 14, 2023).

 24.1**

 Power of Attorney (incorporated by reference to the signature page of the Annual Report on Form 10-K filed with the Securities and Exchange Commission on April 1, 2024).

 31.1*

 Certification of the Principal Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

 31.2*

 Certification of the Principal Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

 31.3*

 Certification of the Principal Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

 31.4*

 Certification of the Principal Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

 32.1***

 Certification of the Principal Executive Officer and Principal Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.

 104*

 *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.

 CLEARSIGN TECHNOLOGIES CORPORATION

 By:

 /s/ Colin J. Deller

 Colin J. Deller

 Chief Executive Officer

 By:

 /s/ Brent Hinds

 Chief Financial Officer

 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.

 /s/ Colin J. Deller

 Colin J. Deller

 Chief Executive Officer and Director

 (Principal Executive Officer)

 /s/ Brent Hinds

 Chief Financial Officer

 (Principal Financial and Accounting Officer)

 *

 Robert T. Hoffman Sr., Director

 *

 Judith S. Schrecker, Director

 *

 Catharine Marie de Lacy, Director

 /s/ David M. Maley

 David M. Maley, Director

 * /s/ Colin J. Deller

 Colin J. Deller, Attorney-in-Fact