I'll grant you that they don't know your donations and major tax deductibles. But your medical expenses would have to be very high before you would even report

I'll grant you that they don't know your donations and major tax deductibles. But your medical expenses would have to be very high before you would even report them to IRS in the first place. Do you directly spend more than 10% of your gross income on medical expenses? No? Then you can't deduct them. In addition, most medical expense reporting is already reported to IRS. They literally get your whole pay stub information - gross pay, withholdings, 401k, medical deductions, pre-tax expenses, etc... PS: I ran a company in one of the "high regulation" EU countries and the amount of tax prep I do today in USA jumped from 30 min per year for myself and 3 employees to 30h per year myself! Oh... I didn't have to pay anything to file my tax documentation online and I got my estimated tax docs pre-filled by the tax authorities.