During an interview with the Economist, President Trump was asked about his tax returns.

During a recent interview with the Economist, President Trump was asked if he would consider releasing his tax returns to appease Democrats who have stated that as a prerequisite for certain aspects of the proposed tax reforms.
Trump responded, "I don’t know. That’s a very interesting question. I doubt it...Because they’re not going to…nobody cares about my tax return except for the reporters. Oh, at some point I’ll release them. Maybe I’ll release them after I’m finished because I’m very proud of them actually. I did a good job."
Treasury Secretary Steven Mnuchin has echoed similar comments about the president's tax returns.
During a late April press briefing, Mnuchin was asked by one of the reporters, "will the President release his tax returns?"
Mnuchin said in response, "the president has no intention -- the president has released plenty of information and I think has given more financial disclosure than anybody else. I think the American population has plenty of information on this..."
The Trump administration has continued to claim ongoing audit as the reason for not releasing the tax returns.
In late January, White House counselor Kellyanne Conway tweeted, “On taxes, answers (& repeated questions) are same from campaign: POTUS is under audit and will not release until that is completed. #nonews.”
Meanwhile, Senator Elizabeth Warren said in a recent MoveOn.org video, "Donald Trump is hiding something. And we know where he’s hiding it: not in a safe, not in a vault. Nope, he’s hiding it in his taxes."