What makes a taxpayer?

[allodial]

if the writing is the agreement, isnt the tax return one's own admission/certification that their person is a tax payer?

With the, say, 1040 the Revenue Agent is effectively making an assessment before the U.S. Tax Court. IMHO, it important to keep the potential depth and breadth of the paper trail in mind since typically a person isn't going to file a 1040 or a 1041 or an 1120 without some kind of W9, SS-4, SS-5, W8, I-9, W-4, 1099 and such being filed. And it is very much a court of record: the 1040 and the postmarks are records. Losing track of the other evidence I suspect would prevent someone from seeing the remedy due to inability to see the cause. A bank signature card or even paychecks could be part of the evidentiary trail.