Hmm? The instructions say "Who Must File
Unless a filing exclusion applies, a corporation must file Form 4626 to determine whether it is an applicable corporation and, if it is classified as an applicable corporation, to calculate CAMT.
Filing exclusions. A corporation is not required to file Form 4626 if the corporation is:
• An S corporation,
• A regulated investment company (RIC),
• A real estate investment trust (REIT), or
• A corporation that is not required to file Form 4626 for the first tax year beginning after 2022 because it is not an applicable corporation under the simplified method and chooses to apply that method. "

Prepare 4626 https://www.irs.gov/pub/irs-pdf/f4626.pdf

Attach to the 1120 https://accountants.intuit.com/support/en-us/help-article/electronic-filing/attaching-pdfs-business-...