Does iPhone 12 show battery percentage?

On iPhone X and later, you can't see the battery percentage in the status bar. You can however see it in Control Center. Just swipe down from the top-right corner of your display.  For4 more info, see:

Show the battery percentage on your iPhone, iPad, or iPod touch - Apple Support'

Yes it does however you will have to view that in the Control Center. If that is not acceptable then you can install the Battery Widget on your home screen.

Axel F.