Which iOS app version/build number(s) MUST be incremented upon App Store release?

Question

Version/build fields for an iOS app include:

• "Version" CFBundleShortVersionString (String - iOS, OS X) specifies the release versi

Answer 1

The current Apple Technical Note TN2420, Version Numbers and Build Numbers says (my bolding):

4. For iOS apps you can re-use build numbers in different release trains, but you cannot re-use build numbers within the same release train. For macOS apps, you cannot re-use build numbers in any release train.

Unfortunately, this means you can't reuse a build number that tracks to the release train number on iOS when you're trying to release the same build on Mac Catalyst.

In my case, for example, due to some earlier issues, I ended up releasing 1.0.2(4) as a Mac Catalyst app that corresponded to 1.0.2(1) on iOS. Now when trying to release 1.0.3(1) on both, the app fails verification on MacOS because of the build number, while it passes verification on iOS.

I guess now that I am releasing the same app on both iOS and MacOS routinely, I will adopt build numbers that correspond to the date, like 20200111 and increment with a decimal point if I need to change the build number within a given release.