What if Trump doesn't include *all* of his business dealings on his taxes?

Is it possible that he did some transactions, especially foreign transactions, under the table? I ask because a lot of people are convinced that his taxes would show the truth of his Russian ties.

This is a guy who was operating a charity without certification, and the only reason why he was caught was because of investigations that occurred before the election.

tRump is a criminal and he's surrounded by criminal accountants, doctors, lawyers, etc.--- I think he's hiding his returns not just because of what's on them, but due to what's not on them. My guess is that his returns will show that he's not worth any where near 10 billion, and that he didn't pay his fair share of taxes for years...but the smoking bomb will be business transactions that we know took place but aren't included in his tax returns (like that Palm Beach house that was sold to a Russian for twice what he paid).