Since macOS is a modern OS, and since modern means removing all user controls, you can’t manually press any button to force check for updates on a Mac.

But there’s a neat trick to force a check anyway! Using the terminal.

On your keyboard, press command and space to bring up the search, and type in “Terminal” which should show the Terminal app. Open it by pressing Enter our double-clicking the search result in the list.

Inside the terminal, type the following command:

softwareupdate -l

Which will check for updates. Just wait a moment for it to complete.

The output might look like the following:

Software Update Tool

Finding available software
Software Update found the following new or updated software:
* Label: Command Line Tools for Xcode-11.5
	Title: Command Line Tools for Xcode, Version: 11.5, Size: 254254K, Recommended: YES,
* Label: macOS Catalina 10.15.6 Supplemental Update-
	Title: macOS Catalina 10.15.6 Supplemental Update, Version:  , Size: 2734058K, Recommended: YES, Action: restart,

And shortly after it should also trigger a system notification that updates are available (if it found any).

Here’s a bonus tip:

If you click on “Update Now” and it asks to restart, just choose “Not Now” to just download the update without installing immediately after download. This is useful if you have work to do but want to download the update in the background to install when convenient, for example at night or after work.

That’s all there is to it! Happy updating!