# EDGAR Filing Document

**Accession Number:** 0002019804
**File Stem:** 0001104659-26-051678
**Filing Date:** 2026-4
**Character Count:** 4764
**Document Hash:** bc71803480292528adc934702600d49c
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-051678.hdr.sgml**: 20260429

**ACCESSION NUMBER**: 0001104659-26-051678

**CONFORMED SUBMISSION TYPE**: DEFA14A

**PUBLIC DOCUMENT COUNT**: 4

**FILED AS OF DATE**: 20260429

**DATE AS OF CHANGE**: 20260429

**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:** DEFA14A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-42252
- **FILM NUMBER:** 26917758

**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

**UNITED STATES<br>SECURITIES AND EXCHANGE COMMISSION<br>Washington, D.C. 20549**

**___________________**

**SCHEDULE 14A**

**___________________**

Proxy Statement Pursuant to Section 14(a) of<br>the Securities Exchange Act of 1934

Filed by the Registrant ☒ <br> Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material under §240.14a-12

**TERRESTRIAL ENERGY INC.** <br> (Name of Registrant as Specified In Its Charter)

**_________________________________________________________________**

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

☒ No fee required. <br> ☐ Fee paid previously with preliminary materials. <br> ☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

![Graphic](tmb-20260427xdefa14a_a001.jpg)

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| &nbsp;&nbsp;![GRAPHIC](tmb-20260427xdefa14a_bg001.jpg) | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Your Vote Counts! TERRESTRIAL ENERGY INC. 2730 W TYVOLA ROAD, SUITE 100 CHARLOTTE, NC 28217 TERRESTRIAL ENERGY INC. 2026 Annual Meeting Vote by June 10, 2026 11:59 PM ET You invested in TERRESTRIAL ENERGY INC. and it's time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on June 11, 2026. Vote Virtually at the Meeting\* June 11, 2026 10:00 AM EDT Virtually at: www.virtualshareholdermeeting.com/IMSR2026 \*Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V92375-P51165 Get informed before you vote View the Notice and Proxy Statement and Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 28, 2026. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. |

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| &nbsp;&nbsp;![GRAPHIC](tmb-20260427xdefa14a_bg002.jpg) | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click "Delivery Settings". Voting Items Board Recommends V92376-P51165 1. Election of Class I Directors Nominees: 1a. Frederick Buckman For 1b. William Johnson For 1c. Hugh MacDiarmid For 2. To ratify the appointment of UHY LLP as the Company's independent registered public accounting firm for the fiscal year ending December 31, 2026. For 3. To transact such other business, if any, as may properly come before the Annual Meeting or any adjournment or postponement thereof. |

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