Timothy L. O’Brien wrote I Saw Trump’s Tax Returns. You Should, Too for Bloomberg News on May 12. Mr. O’Brien knows something about the Donald and his tax returns. He called Mr. Trump a millionaire in his book, TrumpNation, which prompted Mr. Trump to sue him for libeling him by understating his wealth.* Details are in What Really Gets under Trump’s Skin? A Reporter Questioning His Net Worth, written by Paul Farhi for the Washington Post. (The case was dismissed, but not before Mr. O’Brien got to see returns, subject to a confidentiality order.)

Mr. O’Brien does provide a succession of comments from Mr. Trump about the returns. (Aside: Can anyone truly fathom how irritating another four-plus years with Trump will be?)

January:

“I have very big returns, as you know, and I have everything all approved and very beautiful and we’ll be working that over in the next period of time.”

May 10:

“There’s nothing to learn from them,” and voters have no right to see them.

May 11:

“I’ll release. Hopefully before the election I’ll release, and I’d like to release.”

Then, on May 13, Mr. Trump told George Stephanopoulos on ABC News the tax returns were “none of your business.” Then, he said he did not think voters had a right to see his returns, but that “I will really gladly give them.”

Overlaying the noise has been one constant: the IRS has an active audit covering several years. Until it is completed Mr. Trump claims he cannot release his returns.

So let’s clear up some stuff straight-away. Being audited does not have anything to do with disclosing tax returns. The right to disclose belongs to the taxpayer, not the Internal Revenue Service. The “tax audit” claim is nonsensical.

Presidential candidates have routinely released returns, since at least 1976. When and how many aside, they get released. So not seeing the returns is, rightly or wrongly, exceptional.

As for voters having a right to see the returns, candidates are not legally obligated to release them. But they do, and for very good reasons. Here’s what Mr. O’Brien wrote:

Trump is seeking the most powerful office in the world. Some of the potential conflicts of interest or financial pressures that may arise if he reaches the White House would get an early airing in a release of his tax returns.

So, what can we really learn? Mr. O’Brien mentions income, business activities, charitable giving, and tax planning. Regarding income, the issue in most cases involves underreporting. That might be an issue here, although many suggest that Mr. Trump is not worth as much as he says he’s worth. Regardless, for a man with a vast number of businesses and what is surely a complicated set of affairs, determining actual income will likely be very challenging.

As for business activities, an income tax return does not identify entities owned by the taxpayer, unless he or she receives taxable income from the entity. A balance sheet is far more worthwhile, to establish what someone owns and does, but balance sheets are not documents which individuals file anywhere.

Tax returns do identify charitable gifts for which deductions have been claimed, and since Mr. Trump regularly claims he “pays as little as possible,” Schedule A to his personal return likely reflects his charitable giving. However, if he does make charitable gifts, they may come from business entities. Finding those gifts in those returns—if those returns were ever disclosed—will be much more challenging.

As for tax planning, this does matter. Mr. Trump claims he has no offshore accounts. (Frankly, if he really does “pay as little as possible” that claim is almost surely false.) Other sophisticated tax planning may be evident, but much may not. Still, tax planning allows super-wealthy people to advantage themselves. And, legal or not, voters ought to know about the use of the tax code by the man who wants to lead them.

Finally, tax returns tell us how much tax a taxpayer pays, relative to reported income. Following the law is fine, but defending paying the least possible amount because you think government wastes money—an argument Mr. Trump advances frequently—may be part of the mix for voters deciding who should lead that very government.

No doubt, tax experts—I am not a tax attorney, although my practice touches on tax issues every day—can glean from tax returns much more than I can. And Mr. O’Brien is right about the fact that returns do provide a window into a candidate’s finances, which might expose “conflicts of interest or financial pressures … .”

The head hurts, thinking about all of this. Enough! Show us your tax returns, Donald Trump!!!

*The link goes to the 2015 edition of the book. It was first published years earlier, and updated.