Don't believe me? Simply don't file your taxes next year. You will get a letter from the IRS sent to you that literally tells you what you owe. They know all of your income down to the cent, they know what you owe. This automagical system exists. Yet the only way to "use" it is to either not pay your taxes, or to pay them wrong.
Yet every year, the IRS makes us go through the charade of putting our taxes together and all the work (and money) that it entails, when the whole time they know what we owe already and expects us to pay that unless we can prove them otherwise.