I'm not sure how it works in USA, but here, you give your tax card to company who employs you. On that card it's says which percentage you have to pay, and the company deduct the amount before you pay your salary in to your bank account. Btw, I believe the lowest percentage you pay here, is 38% or thereabouts.

Back in the sixties, you got all your wage (in a brown envelope... or was that back in the fifhties) and had to pay the tax yourself.