That's what they're system would be in essence, you'd get a piece of mail saying this is what you'd pay taking what we know and using the standard deduction. If you want you could calculate any itemized deductions and resumbit.

That's how it works here, in Norway.

That's actually exactly what happened when I failed to file for over a year one time. They sent me all the forms prefilled and asked me to review them and just send them back if correct. Sadly, they weren't.