Sure! And they could know about all your doctor's visits, so they could do your medical expense credits for you and similarly track every move you make in society. Oh, you paid for $257.35 on your VISA credit card ending in 1295 for prescription drugs this year: that's deductible!

Is that what we want?

1) I specifically meant "the information they already have", so you would only have to add that which is additional (e.g. medical expenses).

2) There are probably less bureaucratic ways to deal with subsidising medical expenses. Single payer is the nuclear option, but also applying the tax credit in-store and letting the business apply could be a thing?

That's not what anyone is proposing.