If Donald Trump continues to stonewall on releasing his tax returns, it’s clear that he’s doing so because it’s his choice, not his legal obligation. PHOTOGRAPH BY JOHN MOORE / GETTY

Unlike every major-party Presidential candidate since 1976, Donald Trump will not release his tax returns. He’s being audited by the Internal Revenue Service, he has said, and so he will not release any return, for any year, until the audit is complete. Beyond that, his campaign has made it clear that, regardless of the status of the audit, Trump will not be releasing the returns before November.

In March, two of Trump’s tax lawyers, Sheri Dillon and William Nelson, of Morgan, Lewis & Bockius, released a letter to Trump that said the candidate had interests in roughly five hundred business entities and, thus, “your personal federal income tax returns are inordinately large and complex for an individual.” The lawyers said, further, that prior I.R.S. examinations of his taxes over the previous decade had produced no net deficiency. The letter said that the returns had been under “continuous examination” by the I.R.S. but, curiously, said nothing about how or why that might affect the disclosure of the returns. (When I contacted the firm, Dillon declined to speak to me.)

The law is clear about publicly releasing tax returns. The I.R.S. is prohibited from doing so, but taxpayers themselves have every right to disclose their own returns. Does the existence of an audit change the legal status of public disclosure? The answer is no; Trump can release the returns if he wants to. “He filed these tax returns under penalty of perjury with the I.R.S.,” Scott Michel, a partner at Caplin & Drysdale, a leading tax-law firm, said. “If he were to disclose the returns publicly, he’s not disclosing anything that the I.R.S. doesn’t already know about. A disclosure in and of itself cannot possibly prejudice or hurt him with his audit.”

The main risk of disclosure is political rather than legal. Trump’s returns may show that he pays a very low effective tax rate. They may also show that he gives very little to charity, or show foreign financial entanglements. But there is another, less obvious risk of disclosure, according to Michel. “He knows that if he discloses his tax returns, there will be thousands of tax professionals in this country going over them with a fine-tooth comb,” he said. “And, in the public discussion of the returns, there may be issues in his audit that might not yet have arisen, and the I.R.S. hasn’t found them. The auditing agent may get the idea to ask about something he hasn’t thought about. That’s probably one reason why he may be reluctant to turn them over.” Again, though, this possibility is a personal financial risk for the candidate, not a legal barrier to disclosure.

If Trump were interested in allowing the public to learn something about his finances, he might, Michel suggested, find a middle ground between total nondisclosure (Trump’s current position) and release of the full tax return. (Hillary and Bill Clinton have released their complete tax returns going back several years.) “There are any number of questions that could be asked about what’s on his tax returns that wouldn’t require him to disclose the returns themselves,” Michel said. “How much did he report giving to charity? How much tax have you paid in dollars? What’s the effective tax rate that he paid? Do you have any foreign trusts? Foreign bank accounts? How big is your I.R.A.? This is all stuff that is on the face of a tax return”—that is, the form presented to the I.R.S. “There are many facts that he could disclose without going back on his position of not disclosing the full return because he is under audit,” Michel said.

Trump has said that he seeks to pay as little tax as possible under the law. That’s his right, of course. As Judge Learned Hand observed in 1934, “Any one may so arrange his affairs that his taxes shall be as low as possible; he is not bound to choose that pattern which will best pay the Treasury; there is not even a patriotic duty to increase one's taxes.” The question is not what the law requires but what politics demands. In this and so many other ways, Trump has so far defied Presidential electoral tradition by keeping his returns to himself. And if he continues to stonewall it’s clear that he’s doing so because that’s his choice, not his obligation.