Here’s what we know for sure about Donald Trump’s federal tax bill:

He paid nothing in 1978 and 1979, according to a 1981 report that evaluated his fitness for a casino license in New Jersey, The New York Times reports.

He paid zero again in 1984, based on tax court records. In 1991 and 1993, his casinos in Atlantic City were in such bad shape that his losses might have allowed him to avoid taxes those years as well, and, because he could have carried any unclaimed losses forward, perhaps for years later

Beyond that, we must take Donald Trump’s word for it.

No thanks.

Trump is the first candidate from a major party since 1976 to refuse to release his tax returns. He claims he cannot release them because he’s under audit. But his son, Donald Jr., probably was closer to the mark when he noted in an interview with the Pittsburgh Tribune-Review earlier this month that releasing the tax returns would “distract” from his father’s message.

USA TODAY's Editorial Board: Trump is 'unfit for the presidency'

His rival for the presidency, former Secretary of State Hillary Clinton, suggested other reasons in their debate. Maybe Trump isn’t as rich as he claims. Maybe he’s not very charitable. Or maybe he hasn’t paid federal income taxes in a long while.

“That makes me smart,” he retorted in what sounded like an on-the-spot admission. In an interview with sycophant Bill O’Reilly of Fox News, Trump later said that someone who avoids paying taxes is exactly what the country needs.

Wrong.

If he really hasn’t paid up, it should disqualify him from the presidency.

Think of it:

The candidate who claims the country needs to rebuild its military couldn’t spare a dime of his own money to support our troops. The candidate who wants to boost spending on infrastructure hasn’t pitched in himself like all other hard-working, taxpaying Americans.

If a leading candidate for president is wealthy enough to pay lawyers and accountants to find loopholes and avoid paying federal taxes altogether, the rest of us working stiffs who pitch in for things such as our shared national defense have a right to know that. Maybe we don’t all agree with Trump that taxes only should be paid by people who aren’t as smart as he is.

When Mitt Romney ran for president on the Republican ticket with House Speaker Paul Ryan in 2012, he took plenty of grief from Democrats, a lot of it unfair, for his wealth. But he released his tax returns. In 2011, Romney paid an effective tax rate of 14% and turned over $1.9 million to the federal coffers. That means Romney contributed roughly $304,000 to the defense budget (it consumes 16% of federal spending) and $475,000 to Medicare, Medicaid and a variety of other safety net programs and $114,000 to interest on the national debt.

And what of Trump? We don’t know.

Exasperated at questions about his taxes, Trump told reporters after the debate, “Of course I pay federal taxes.”

Trust me, he says.

No thanks. He can’t be trusted. Trump’s tax returns would answer a number of questions about how he made his money and how his finances work — reasonable things for voters to know for a candidate who seems to frequently use his campaign to market his businesses.

Trump should produce his tax returns to reveal whether he contributes to the shared costs of the democratic republic he wants to govern. Now.