Sure, that would be simple enough for them to mail you a letter with like "we're aware of these incomes from these employers" and any failure to file additional income on your part makes you liable. And of course not filing to claim any credits/deductions on your part just screws your out of your own money.

But then that also assumes the IRS knows your address. Does your employer even report your address when your taxes are withheld from your paycheck? And what if you move in the time between then?