The original Developer ID Certification Authority Sub-CA is expiring on February 1, 2027, meaning certificates issued by it will cease to function. Developers should check their existing certificates for expiration dates on or before February 1, 2027. Affected users need to create a new certificate from the current Developer ID Certification Authority (G2). It is important to update Xcode to version 11.4 or later before creating the new certificate. When prompted, select the G2 Sub-CA as the intermediary. Installer packages (.pkg) signed with an expiring certificate will fail to install after February 1, 2027. Therefore, all installer packages must be re-signed with the new certificate beforehand. Previously signed and notarized Mac apps with a secure timestamp will continue to work. For any future updates to Mac apps, they must be signed with the new certificate. This new certificate should also include a secure timestamp for notarization.