THERE IS AN UPDATE FOR MY MAC, THE macOS Catalina 10.15.5
Why my Mac wont update when I click to update? It's keep restarting only and didn't continue to update?
MacBook Air 13″, macOS 10.15
What build number do you see? You can see this by going to the Apple menu, About this Mac, and then click on where it says 'Version 10.15.5'. If you have the latest then you should see build 19F101. If that's what you see then you're up-to-date. Anything less than that and what you're probably missing is https://support.apple.com/en-ie/HT211215
If your build number isn't the one listed above, you could try manually downloading the supplement update from https://support.apple.com/kb/DL2044?viewlocale=en_US&locale=en_US