[mixmastamyk]

They do know almost everything and learning more every day. Of course there are extenuating circumstances, which you will list and have to prove if a question comes up. This is not an excuse for tax filing being more difficult than it needs to be.

[compiler-guy]

The great-grandparent's claim is that they already know. They don't already know. I can list two dozen things off the top of my head that they don't already know.

Should tax filing be easier? Sure. But, "They already know how much you owe." is patently false.

[mixmastamyk]

It's an approximation, and they will come looking for it if you don't file. So yes, it does have some level of truth (and force) behind it.