The majority of US voters believe President Trump’s reluctance to release his tax returns indicates he has something to hide.

 The majority of U.S. voters believe President Trump's reluctance to release his tax returns indicates he has something to hide. That was the response given by 52% of the roughly 1,250 participants in a Quinnipiac University National Poll conducted from February 16 to 19.  Only 19% said an audit was keeping the president from releasing the tax information, and 14% didn't find either explanation particularly compelling. Trump reportedly said during the 2016 presidential campaign that he would release his return when an IRS audit is complete. 
He has since indicated that he "might release them" after he is "out of office." Trump has also asserted that nobody outside of the media really cares about the documents, but the recent Quinnipiac poll suggests otherwise.
67% of those polled said Trump's returns should be made available.  "Every listed party, gender, education, age and racial group, except Republicans, says Trump should release his tax returns," according to a university press release.