Company: CCIXW
Filing Date: 2025-11-24
Form Type: DEF 14A
Source: 0001193125-25-293828
Chunk: 4

Company: Churchill Capital Corp IX/Cayman
Filing Date: 2025-11-24
Form: DEF 14A
Chunk 4
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 close of business on November 18, 2025 (the “ Record Date”) as the date for determining the shareholders entitled to receive notice of and vote at the Meeting and any adjournment thereof. Only holders of record of the Ordinary Shares on that date are entitled to have their votes counted at the Meeting or any adjournment thereof. On the Record Date, there were 29,475,000 Class A Ordinary Shares and 7,187,500 Class B Ordinary Shares issued and outstanding. Our outstanding warrants do not have voting rights in connection with the Auditor Ratification Proposal. A shareholder who is entitled to attend and vote at the Meeting is entitled to appoint one or more proxies to attend and vote instead of that shareholder, and such proxyholder need not be our shareholder. Shareholders will have the opportunity to present questions to our management (the “ Management”), including regarding our Annual Report on Form 10-Kfor the fiscal year ended December 31, 2024, as filed with the SEC on March 31, 2025 (the “ 2024 Annual Report”), at the Meeting. This proxy statement (the “ Proxy Statement”) contains important information about the Meeting and the Auditor Ratification Proposal. Whether or not you plan to attend the Meeting, we urge you to read this material carefully and vote your shares. This Proxy Statement is dated November 24, 2025 and is first being mailed to shareholders on or about November 24, 2025.

This Notice of the 2025 Annual Meeting, the Proxy Statement, including the proxy card, and our 2024 Annual Report are also available at www.cstproxy.com/churchillcapitalix/2025 .

| November 24, 2025 |     | By Order of the Board of Directors     |
|:------------------|:----|:---------------------------------------|
|                   |     | /s/ Michael Klein                      |
|                   |     | Michael Klein                          |
|                   |     | Chief Executive Officer, President and 
 Chairman of the Board of Directors     |

TABLE OF CONTENTS

|                                                      |     | Page |
| CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS |     |    1 |
| QUESTIONS AND ANSWERS ABOUT THE MEETING              |     |    2 |
| BACKGROUND                                           |     |    8 |
| THE MEETING                                          |     |    9 |
| THE AUDITOR RATIFICATION PROPOSAL                    |     |   13 |
| BENEFICIAL OWNERSHIP OF