Presidential candidates should have total transparency, and tax returns are the bare minimum when it comes to being honest with the public. Of course, Trump has never been honest with the public, and releasing his tax returns would admit his ties to Russian oligarchs as well as the fact that he's probably not even a billionaire.
Normally someone's tax returns are private , but Donald Trump has made a campaign issue and based his platform on how much money he has and how good he is at a running a business. He should be able to prove that what he says is true and that he is not making stuff up.
His personal tax returns aren't important. There is no other job in America that requires a person to share their tax returns. We are in such dire condition in this country that his tax returns are totally unimportant. I am concerned only about what he can do to fix the country.
Releasing tax returns isn't an important issue at all, it's just something that one side or the other uses to make it look like the opposition is hiding something. If Trump isn't legally bound (he's not), then it should be a non-issue. Of course, this entire election has been thinly veiled comments about the "other side," so this sort of bogus line of reasoning fits right in.