I'll let Trump comment in my place (thank you, Mr. President):

Feb. 25, 2015: "I have no objection to showing tax returns."
Jan. 24, 2016: "We're working on that now ... and at the appropriate time you'll be very satisfied."
Feb. 25, 2016: "I will absolutely give my return."
May 10, 2016: "I'll release. Hopefully before the election I'll release."
Sept. 26, 2016: "I'm under a routine audit ... as soon as the audit's finished, it will be released."
Oct. 9, 2016: "As soon as my routine audit is finished, I'll release my returns. I'll be very proud to. They're actually quite great."