2nd Trump's daddy cheated taxes along with Trump and his siblings which the NY Times exposed.
Trump has inflated and deflated assets whenever it was to his advantage and with taxes, financial institutions, and insurance companies that's called fraud.
Trump is a crook. His Daddy was a crook. His Grandfather was a Pimp and Drug dealer. The apple doesn't fall far from the tree.
Trump has stiffed small vendors and hapless people (see Trump University) what makes you think he hasn't stiffed the IRS? How naïve but then there are people who are full fledged members of the Trump cult.
Oh and you seem to know very little about taxes and income. The only item you do not have to prove for tax purposes is income. That's up to the IRS to prove.