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

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

~~Date of Report (Date of earliest event reported): November 21, 2025~~

Date of Report (Date of earliest event reported): January 29, 2026

TERRESTRIAL ENERGY INC.

(Exact name of registrant as specified in its charter)

Delaware		001-42252		98-1785406
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)


Delaware		001-42252		98-1785406
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

2730 W. Tyvola Road, Suite 100

Charlotte, NC 28217

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (646) 687-8212

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

~~¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)~~

¨☐ Written ~~Soliciting~~communications ~~material~~ pursuant to Rule ~~14a-12~~425 under the ~~Exchange~~Securities Act (17 CFR ~~240~~230.~~14a-12~~425)

~~¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))~~

¨☐ Soliciting ~~Pre-commencement~~material ~~communications~~ pursuant to Rule ~~13e~~14a-~~4(c)~~12 under the Exchange Act (17 CFR 240.~~13e~~14a-~~4(c~~12))

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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, par value $0.0001 per share	IMSR	The Nasdaq Stock Market LLC
Redeemable Warrants, each whole warrant exercisable for one Common Stock at a price of $11.50 per share	IMSRW	The Nasdaq Stock Market LLC

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, par value $0.0001 per share	IMSR	The Nasdaq Stock Market LLC
Redeemable Warrants, each whole warrant exercisable for one Common Stock at a price of $11.50 per share	IMSRW	The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

~~Emerging growth company x~~

IfEmerging ~~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. ¨☒

~~EXPLANATORY NOTE~~

AsIf ~~previously~~an ~~reported,~~emerging ongrowth ~~March 28~~company, ~~2025,~~indicate ~~Terrestrial~~by ~~Energy~~check ~~Inc. (the~~mark ~~“Registrant”~~if or the ~~“Company”,~~registrant ~~formerly~~has ~~known~~elected asnot ~~HCM II Acquisition Corp. (“HCM II”) prior~~ to use the ~~Business~~extended ~~Combination~~transition ~~described~~period ~~herein)~~for ~~consummated~~complying ~~its previously announced business combination (the “Business Combination”)~~ with ~~the~~any ~~entity~~new ~~formerly~~or ~~known~~revised asfinancial ~~Terrestrial~~accounting ~~Energy~~standards ~~Inc.~~provided ~~and now named Terrestrial Energy Development Inc. (“Legacy Terrestrial Energy”),~~ pursuant to ~~the~~Section ~~terms of that certain Business Combination Agreement~~ 13(~~as amended, the “Business Combination Agreement”) by and among the Company, Legacy Terrestrial Energy, and HCM II Merger Sub Inc.,~~ a ~~direct, wholly owned subsidiary of HCM II (“Merger Sub”~~). ~~Pursuant to the terms~~ of the ~~Business~~Exchange Combination Agreement, Merger Sub merged with and into Legacy Terrestrial Energy, with Legacy Terrestrial Energy as the surviving company and becoming a wholly owned subsidiary of the Registrant (the “Merger”)Act. ☐

~~Item 4.01 Changes in Registrant’s Certifying Accountant.~~

~~(a) Dismissal of independent registered public accounting firm.~~

~~The~~Item report of Withum on the financial statements of HCM II for the year ended December 31, 2024 did not contain an adverse opinion or a disclaimer of opinion, and was not qualified or modified as to uncertainties, audit scope or accounting principles except for the explanatory paragraph describing an uncertainty about HCM II’s ability to continue as a going concern7.01 ~~The~~Regulation ~~report~~FD of Withum on HCM II’s report on the financial statements of HCM for the year ended December 31, 2024 included an emphasis of matter paragraph with respect to the restatement of financial statements to correct the inclusion of a transaction with HCM II’s underwriter in the related party transaction footnoteDisclosure.

During the period from April 4, 2024 (HCM II’s inception) through September 30, 2025 and the subsequent interim period preceding Withum’s dismissal, there were no (i) disagreements with Withum on any matter of accounting principles or practices, financial statement disclosures or auditing scope or procedures, which if not resolved to Withum’s satisfaction, would have caused Withum to make reference to the subject matter of the disagreement in connection with its report or (ii) reportable events as defined in Item 304(a)(1)(v) of Regulation S-K under the Securities Exchange Act of 1935, as amended.

~~The~~On ~~Registrant~~January ~~has~~29, ~~provided Withum~~2026, ~~with~~Terrestrial aEnergy ~~copy~~Inc. ofissued ~~the~~a ~~foregoing~~letter ~~disclosures~~providing ~~and requested that Withum furnish the Registrant with~~ a ~~letter~~corporate ~~addressed~~update to ~~the Commission stating whether it agrees with the statements made by the Registrant set forth above~~shareholders. A copy of the letter ~~from Withum, dated November 24, 2025,~~ is ~~filed~~furnished herewith as Exhibit 16 99.1 toand ~~this~~incorporated ~~Current~~herein ~~Report~~by reference.

~~(b) Disclosures regarding the new independent auditor.~~

OnThe ~~November~~information ~~21,~~set ~~2025,~~forth ~~the~~under ~~Audit~~this ~~Committee~~Item ~~approved~~7.01, ~~the~~including ~~engagement~~Exhibit ~~of UHY~~99.1, ~~LLP~~is ~~(“UHY”)~~intended ~~as the Registrant’s independent registered public accounting firm~~ to ~~audit~~be ~~the~~furnished ~~consolidated~~and ~~financial statements~~shall ofnot ~~the~~be ~~Registrant~~deemed as“filed” ~~of and~~ for ~~the~~purposes ~~year ended December 31, 2025. UHY served as the independent registered public accounting firm~~ of ~~Legacy~~Section ~~Terrestrial~~18 ~~Energy prior to the consummation~~ of the ~~Merger.~~Securities ~~During~~Exchange ~~the~~Act ~~period~~of ~~from April 4~~1934, ~~2024~~as amended (~~HCM~~the ~~II’s~~“Exchange ~~inception~~Act”) ~~to September 30~~, ~~2025~~or ~~and~~otherwise ~~the~~subject ~~subsequent interim period through November 21, 2025, HCM II did not consult with UHY with respect~~ to ~~(i)~~ the ~~application~~liabilities of ~~accounting~~that ~~principles to a specified transaction~~section, ~~either~~nor ~~completed~~shall orit ~~proposed,~~be ~~the~~deemed ~~type~~incorporated ofby ~~audit~~reference ~~opinion~~in ~~that might~~any befiling ~~rendered~~under on the ~~financial~~Securities ~~statements~~Act of ~~HCM II~~1933, ~~and neither a written report nor oral advice was provided to HCM II that UHY concluded was an important factor considered by HCM II in reaching a decision~~ as ~~to any accounting~~amended, ~~auditing~~ or ~~financial~~the ~~reporting~~Exchange ~~issue~~Act, or ~~(ii)~~except ~~any~~as ~~other~~expressly ~~matter~~set ~~that~~forth ~~was~~by ~~the~~specific ~~subject~~reference ofin asuch ~~disagreement or a reportable event (as defined above)~~filing.

Item 9.01. Financial Statements and Exhibits.

Exhibit		Description
16.1		Letter from WithumSmith+Brown, PC to the SEC, dated November 24, 2025.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).


Exhibit		Description
99.1		Letter to Shareholders, dated January 29, 2026
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURES

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

Date: November 24, 2025	TERRESTRIAL ENERGY INC.
	By:	/s/ Brian Thrasher
	Name:	Brian Thrasher
	Title:	Chief Financial Officer

Date: January 29, 2026	TERRESTRIAL ENERGY INC.

	By:	/s/ Brian Thrasher
	Name:	Brian Thrasher
	Title:	Chief Financial Officer

Filing Compare · Terrestrial Energy Inc. /DE/