That Donald Trump is a cagey one, saying he wants to wait until the IRS finishes auditing his tax returns before he decides whether to release them to the public.

There’s nothing that says presidential candidates have to release their tax returns, but there is some value to it.

One of the things that can be learned from a candidate’s tax returns is what a person’s income was and the tax rate that was paid on that income. Did he pay the full 39.6 percent that those in the nation’s top tax bracket are subject to, or something less?

In Trump’s case, releasing his tax returns would allow the public to see how the numbers square with the candidate’s public statements about his wealth, donations to charity and use of deductions that allow people to legally reduce the amount they pay to the government.

Wealth and income are not the same, of course, but they are not unrelated, either, and income can provide some clues to how wealthy a person is. Trump’s income taxes could, for instance, provide insight into his investment holdings.

Could they also show whether he paid nothing at all?

The Washington Post reported in May that the last time Trump’s income taxes were made public – back in 1981, when his returns were released by gaming regulators in New Jersey – "the wealthy Manhattan investor had for at least two years in the late 1970s taken advantage of a tax-code provision popular with developers that allowed him to report negative income."

In other words, Trump paid nothing back then.

If he paid zero taxes in recent years, that’s probably the kind of thing the public would like to know, especially in light of the fact that he has criticized others for avoiding taxes.

But Trump makes no secret of his distaste for contributing to the public treasury.

"I try and pay as little tax as possible, because I hate what they do with my tax money," he told NBC News. "I hate the way they spend our money."

But Trump says his tax rate is "none of your business."

He’s welcome to that position, but the public has a funny way of deciding for itself what is and isn’t its business. In fact, voters has come to expect that candidates running for president disclose their recent income tax returns prior to an election.

Every presidential candidate since Richard Nixon has released tax returns prior to an election, with the exception of Gerald Ford, who released summaries (how’d that work out for him?).

In Nixon’s case, he released his tax returns while he was under audit, and there’s no reason an audit should stop Trump from doing the same.

Trump has cited his wealth, business experience and financial acumen as a reason people should vote for him.

That’s all well and good, but voters shouldn’t be required to take his word for it when there are numbers that could provide a more objective view of Trump’s financial situation.