The user you're replying to simplified the process some. There is no government website that will tell you exactly what you owe. You always are doing the math y

The user you're replying to simplified the process some. There is no government website that will tell you exactly what you owe. You always are doing the math yourself and then hoping that you did the math correctly. Even for a refund, it's up to you to tell the government that you overpaid. The reason you might have heard a lot of fuss around hiring more IRS agents, is that the only way to validate these numbers if to be audited (broadly speaking). There might be some automated checks for very obvious things but much of the process is self-reported. The software is largely there to help people with the math and accounting for all of the deductions that the average person may be eligible for (mortgage interest being the largest and most common).