Every presidential nominee from both parties has done it for the past four decades
, and there are loud calls from pundits and even Republican leaders such as House Speaker Paul Ryan for Trump to release them.
Now his supporters are joining the chorus.
"I don't know what the hold-up is," said Wayne Kemp, a retiree and Trump supporter in Orlando, Florida.
Without releasing his tax returns, Trump leaves a lot of questions unanswered about his wealth, his tax rate, his charitable donations and where he gets his funding for his real estate deals.
Trump claims he can't because he's under audit by the Internal Revenue Service. Tax experts don't buy it.
The law does not prevent anyone from releasing their tax returns under audit. Furthermore, Trump's campaign confirmed that the GOP candidate is not under audit for 2008 or earlier. Trump could release those returns. But so far, he has not.
Last week, Donald Trump, Jr. added to the controversy by telling the Pittsburgh Tribune-Review that his father's tax returns were too complicated for regular people to understand.
"Because he's got a 12,000-page tax return, that would create ... financial auditors out of every person in the country asking questions that would detract from (his father's) main message," Trump, Jr. said Wednesday.