*edit: I'm getting a lot of replies saying there's nothing keeping him from releasing his returns while being audited. I'm well aware, but as has been pointed out by talmand, having the IRS sign off on his audit helps shore up his defense if anything in there looks questionable to people. Also, he obviously doesn't see any reason to give people potential ammunition. He stands to gain almost nothing from releasing his tax returns. Even if they're flawless and he's paying 60% tax (we obviously know that isn't the case), at best people would shrug and move on. At worst, they would find something to hammer him on, whether valid or not, and the audit would still be pending, giving him little defense to the accusations.