# EDGAR Filing Document

**Accession Number:** 0002019804
**File Stem:** 0001104659-26-036902
**Filing Date:** 2026-3
**Character Count:** 8481
**Document Hash:** 2dcb14177c16912df0d5469f9deb65b1
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-036902.hdr.sgml**: 20260330

**ACCESSION NUMBER**: 0001104659-26-036902

**CONFORMED SUBMISSION TYPE**: POS EX

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260330

**DATE AS OF CHANGE**: 20260330

**EFFECTIVENESS DATE**: 20260330

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Terrestrial Energy Inc. /DE/
- **CENTRAL INDEX KEY:** 0002019804
- **STANDARD INDUSTRIAL CLASSIFICATION:** FABRICATED PLATE WORK (BOILER SHOPS) [3443]
- **ORGANIZATION NAME:** 04 Manufacturing
- **EIN:** 981785406
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** POS EX
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-291796
- **FILM NUMBER:** 26813667

**BUSINESS ADDRESS:**
- **STREET 1:** 2730 W. TYVOLA ROAD, SUITE 100
- **CITY:** CHARLOTTE
- **STATE:** NC
- **ZIP:** 28217
- **BUSINESS PHONE:** 203-930-2200

**MAIL ADDRESS:**
- **STREET 1:** 2730 W. TYVOLA ROAD, SUITE 100
- **CITY:** CHARLOTTE
- **STATE:** NC
- **ZIP:** 28217

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** HCM II Acquisition Corp.
- **DATE OF NAME CHANGE:** 20240415

**As filed with the U.S. Securities and Exchange Commission on March 30, 2026**

**Registration No. 333-291796**

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**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

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**POST-EFFECTIVE AMENDMENT NO.1**

**TO**

**FORM S-1 REGISTRATION STATEMENT**

***UNDER***

***THE SECURITIES ACT OF 1933***

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**TERRESTRIAL ENERGY INC.**

(Exact name of registrant as specified in its charter)

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| | | |
|:---|:---|:---|
| **Delaware** | **3443** | **98-1785406** |
| (State or other jurisdiction of<br>incorporation or organization) | (Primary Standard Industrial<br>Classification Code Number) | (I.R.S. Employer<br>Identification Number) |

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**2730 W. Tyvola Road, Suite 100**

**Charlotte, NC 28217**

**(646) 687-8212**

(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

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**Simon Irish**

**Chief Executive Officer**

**2730 W. Tyvola Road, Suite 100**

**Charlotte, NC 28217**

**(646) 687-8212**

(Name, address, including zip code, and telephone number, including area code, of agent for service)

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*Copies to:*

**Sean Jones**

**Coleman Wombwell**

**K&L Gates LLP**

**300 South Tryon Street**

**Suite 1000**

**Charlotte, NC 28202**

**(704) 331-7406**

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**Approximate date of commencement of proposed sale to the public:** From time to time after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box: ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☒ **333-291796**

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 ☐ <br> Non-accelerated filer ☒ Smaller reporting company ☒ <br> 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 7(a)(2)(B) of the Securities Act: ☐

**This Post-Effective Amendment No. 1 to the Registration Statement Shall become effective immediately upon filing with the Securities and Exchange Commission in accordance with Rule 462(d) under the Securities Act.**

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**EXPLANATORY NOTE**

This Post-Effective Amendment No. 1 (this "Amendment") to the Registration Statement on Form S-1 of Terrestrial Energy Inc. (File No. 333-291796), initially filed on November 26, 2025, and declared effective by the Securities and Exchange Commission on December 23, 2025 (the "Registration Statement"), is being filed as an exhibit-only filing solely to file a consent of UHY LLP with respect to its report dated March 30, 2026 relating to the financial statements of Terrestrial Energy Inc. for the years ended December 31, 2025 and December 31, 2024 contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2025 and included in the Prospectus Supplement No. 1 dated March 30, 2026 filed pursuant to Rule 424(b)(3), filed herewith as Exhibit 23.1 (the "Consent"). Accordingly, this Amendment consists only of the facing page, this explanatory note, Item 16 of Part II of the Registration Statement, the signature pages to the Registration Statement, and the Consent. The prospectus and the balance of Part II of the Registration Statement are unchanged hereby and have been omitted.

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**Part II**

**INFORMATION NOT REQUIRED IN PROSPECTUS**

**Item 16. Exhibits and Financial Statement Schedules.**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) **Exhibits**.

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| | | |
|:---|:---|:---|
| **Number** |  | **Description** |
| 23.1 | \* | [Consent of UHY LLP](tmb-20260330xex23d1.htm) |

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\* Filed herewith

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**SIGNATURES**

Pursuant to the requirements of the U.S. Securities Act of 1933, as amended, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Charlotte, State of North Carolina, on March 30, 2026.

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| | |
|:---|:---|
| **TERRESTRIAL ENERGY INC.** | **TERRESTRIAL ENERGY INC.** |
| By: | /s/ Simon Irish |
| Name: | Simon Irish |
| Title: | Chief Executive Officer |

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Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons in the capacities and on the dates indicated below.

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| | | |
|:---|:---|:---|
| **Signature** | **Title** | **Date** |
| /s/ Simon Irish | Chief Executive Officer and Director | March 30, 2026 |
| Simon Irish | (*Principal Executive Officer*) |  |
| /s/ Brian Thrasher | Chief Financial Officer | March 30, 2026 |
| Brian Thrasher | (*Principal Financial and Accounting Officer*) |  |
| \* | Chairman of the Board of Directors | March 30, 2026 |
| Frederick Buckman |  |  |
| \* | Director | March 30, 2026 |
| Shawn Matthews |  |  |
| \* | Director | March 30, 2026 |
| Hugh MacDiarmid |  |  |
| \* | Director | March 30, 2026 |
| David Hill |  |  |
| \* | Director | March 30 2026 |
| Charles Pardee |  |  |
| \* | Director | March 30, 2026 |
| Robert W. Jones |  |  |
| \* | Director | March 30, 2026 |
| William Johnson |  |  |
| \* | Chief Technology Officer and Director | March 30, 2026 |
| David LeBlanc |  |  |

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| | |
|:---|:---|
| By: | /s/ Simon Irish |
| Name: | Simon Irish |
|  | Attorney-in-fact |

---

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## Exhibit 23.1

**Exhibit 23.1**

**INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM'S CONSENT**

We hereby consent to the inclusion in this Post-Effective Amendment No. 1 to the Registration Statement of Terrestrial Energy Inc. (the "Company") on Form S-1 (File No. 333-291796) of our report dated March 30, 2026, with respect to our audits of the consolidated financial statements of the Company as of December 31, 2025 and 2024 and for the two-year period ended December 31, 2025, appearing in the Prospectus Supplement, which is part of this Registration Statement.

We also consent to the reference to our Firm under the heading "Experts" in such Prospectus.

/s/ UHY LLP

Melville, NY

March 30, 2026

An Independent Member of Urbach Hacker Young International

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