Terrestrial Energy Inc. /DE/

You may vote during the Annual Meeting by logging into www.virtualshareholdermeeting.com/IMSR2026 and entering your stockholder information provided on the Notice previously mailed to you, by submitting a proxy by mailing the enclosed proxy card, or by submitting voting instructions by telephone or on the Internet. Instructions regarding submitting your proxy or voting instructions by telephone and on the Internet are included on the enclosed proxy card. You may not submit your voting instructions by telephone or on the Internet after 11:59 p.m. Eastern Time on Wednesday, June 10, 2026. If you choose to submit a proxy by mail, please mark, sign, and date the proxy card and return it in the enclosed postage-paid envelope. If a bank, broker, or other nominee (“broker”) holds your shares, you will receive voting instructions directly from the broker.

You will need to obtain your own live webcast access if you choose to attend the Annual Meeting and/or vote. To attend and participate in the Annual Meeting, you will need the 16-digit control number included on your proxy card or on the instructions that accompanied your proxy materials. If your shares are held in “street name,” you should contact your broker to obtain your 16-digit control number or otherwise vote through the bank or broker. The Annual Meeting webcast will begin promptly at 10:00 a.m., Eastern Time. We encourage you to access the Annual Meeting prior to the start time. Online check-in will begin shortly before the Annual Meeting on June 11, 2026.