Trump said, “You don’t learn anything from a tax return. I think nobody knows more about taxes than I do, maybe in the history of the world. Nobody knows more about taxes. You can learn very little from a tax return.” http://www.pbs.org/newshour/
Asked, “What will you do if the tax returns come out as part of an October surprise?” Trump's unsurprising answer was, “I’ll say they aren’t mine.”(1)
Which is a good thing, because voters don't really want Trump's numbers, they want official IRS tax return numbers.
In a 2008 deposition, Trump under oath claimed that land in Westchester County, N.Y., had doubled in value over the course of a year. Asked, “Do you have any basis for that view other than your own opinion?”. His response was, “I don’t believe so, no.”(1)
All candidates for President are required to fill out a public financial disclosure report. In Trump's 92 page report, dated 7/15/15, he listed a New York golf club he owned as being worth more than $50 million. But, in an effort to reduce his property taxes, Trump filed a lawsuit claiming the property was worth only $1.4 million, which the town assessor said was crazy low.(2) Trump has since revised his estimate to $9 million.(3)
(2) 3/12/16 https://www.theguardian.com/2016/mar/12/briarcliff-manor-golf-course-tax
(3) 5/16/16: http://abc7ny.com/politics/trump-engaged-in-tax-battle