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Donald Trump has maintained for seven months that he cannot release his tax returns because he is being audited by the Internal Revenue Service, making him the first major-party nominee for president since President Gerald Ford to withhold such records from the public.

Last week, his son Donald Trump Jr. gave a different excuse for not releasing the documents, saying the returns would be "distracting."

With so much speculation surrounding them, the GOP nominee and wealthy businessman's tax filings may just be the most wanted information of the 2016 campaign.

While Trump insists that voters "don't care" about his returns, journalists, Democratic opponent Hillary Clinton and many voters insist the public wants to see them. New York Times Executive Editor Dean Baquet and Washington Post Associate Editor Bob Woodward told a Harvard University forum this month they would love to publish Trump's returns if someone leaked them, even if it meant serving jail time. Some Americans have wondered whether Trump actually paid any taxes during some years - and if he is as rich as he says he is.

"If someone were to release the returns right now, they might be able to change the outcome of the election," said Joseph Thorndike, a tax historian and director of the non-partisan Tax History Project at Tax Analysts. "It's a very tempting prospect."

In the age of Edward Snowden and the Internet troublemaker Anonymous, we wondered exactly why Trump's tax returns have not come to light. One big obstacle is that leaking confidential tax records is against the law, punishable by a $5,000 fine, up to five years in jail or both.

"The IRS and our employees take our role to protect confidential tax information very seriously," chief agency spokesman Matthew Leas said, "and we have high standards and tight controls in place for this sensitive data."

Trump's state tax returns may be on file at New York state's tax office. A spokesman for the Department of Taxation and Finance said protecting taxpayer information is "paramount" to its mission.

The Post reached out to the Washington law firm Morgan, Lewis and Bockius, Trump's tax attorneys, for comment about its own security protocols and didn't receive a reply.

Here's a primer on what we don't know about Trump's taxes — and may never learn.

Q. How many people have seen — or could see — the GOP nominee's returns?

A. According to tax experts and former IRS employees, tens of thousands of people have access to Trump's tax information, if not his complete returns. Revenue agents, customer service staff and employees at walk-in tax assistance centers, plus a smaller number of federal contractors, use a master computer that shows a summary of everyone's return. Once they enter a name or Social Security number, these employees could go further into the record, much like scanning a bank account.

"It would take ten minutes," said Richard M. Schickel, who retired from the IRS in 2013 as a senior revenue officer and wrote a book about the agency. The computer is a "museum of tax information," he said: "Everyone is on it. You, your grandfather, your great uncle."

Q. So what prevents a curious IRS employee from taking a peek or passing Trump's return to a reporter?

A. For one thing, it's a felony to disclose confidential tax information. Federal employees could lose their job, pension, freedom and reputation.

The IRS says its 84,000 employees must attend annual trainings on taxpayer confidentiality. To identify snoopers, IRS computers track the electronic movements of all employees and contractors. Even an employee who legitimately opens the tax return of a neighbor of a high-profile taxpayer like Trump could be flagged, former IRS officials say.

Not surprisingly, the IRS does not discuss specific tax returns.

Q. But what if the employee just didn't care about the consequences?

It's unlikely, say former IRS officials.

"People underestimate the importance of culture," said Fred Goldberg, a former IRS commissioner who has called on Trump to release his returns. ". . . The likelihood of someone at the IRS leaking this information is at most quite remote."

Q. But couldn't an IRS employee take a peek at Trump's tax returns without anyone knowing?

A. Nope. Even looking at a return without good reason would throw the "white hot light of suspicion" on an employee, said Mark Matthews, an ex-IRS deputy commissioner. The agency's computers, however outdated, know who is doing what.

Q. What if Trump files paper returns? Where are they — and could someone get to them?

A. Although a photo of himself Trump tweeted last year implied he filed a paper return — as did his son's recent comment that the return is 12,000 pages long — we don't really know how he files.

If Trump uses his New York address as his legal filing address, his return would be filed to the IRS Processing Center in Kansas City, according to former IRS employee Schickel. The paper file would be kept there for between three and five years, then transferred to federal records retention centers, he said.

But tax experts and former IRS employees said a return as complicated as Trump's is likely filed electronically. The thick binders in the photo could be supporting documents, and his accountants may use their own software to integrate records from Trump's assets and real estate businesses, experts said.

His returns would immediately be scanned electronically for red flags like a spike in income or debt. When there are enough of these red flags, an audit is triggered.

Trump claims he has been under audit since 2002. Public figures and other notable taxpayers like Trump usually have their returns handled by trusted and experienced revenue agents. Informally, this is known as the "Celebrity Audit Unit," Schickel said.

Q. Doesn't the IRS get hacked a lot?

A. In 2015, identity thieves used stolen Social Security numbers and other data they got from outside the IRS to hack into a database containing prior-year tax information. The thieves gained access to as many as 330,000 accounts and attempted to break into another 280,000.

"The U.S. landscape is very risky now for anyone residing in the country," said Gabriella Coleman, a McGill University anthropologist and the author of "Hacker, Hoaxer, Whistleblower, Spy: The Many Faces of Anonymous."

While there's a "lot of desire" for Trump's tax records, Coleman said, more and more hackers outside the United States face extradition to this country, chilling their public disclosures.

Q. Would a news organization that received the returns get in trouble?

A. Federal law prohibits "any person" from printing, publishing or soliciting tax return information without the taxpayer's authorization.

The penalties for improperly disclosing tax information were strengthened in the late 1990s, putting new restrictions, procedures and an internal tracking system in place to address concerns about unauthorized tax return browsing.

First Amendment experts note that while the media could be prosecuted for publishing Trump's tax returns, a news organization could also assert a First Amendment defense. In the case of the Pentagon Papers, for example, The Post argued publication served an important public interest.

But those arguments would not be sure winners, experts said. And a member of the media would need to consider risks to his or her sources in any investigation of who shared Trump's tax information.

"The courts could say: If the public thinks the tax returns are so important, let it demand that the candidate authorize the IRS to release them on pain of losing votes," said Jonathan Zittrain, a privacy expert and professor at Harvard Law School.

Q. Has anyone ever leaked a tax return?

A. Although neither the IRS nor the Treasury Inspector General for Tax Administration would say how many people have been caught sharing returns outside the IRS, the agency says it investigates those accused of such behavior.

In fiscal year 2015 alone, the IRS identified 341 employees or contractors who improperly accessed a tax return, meaning they called up the information on their computer.

Most of these were inadvertent, but 51 viewings were intentional — meaning that about once per week, someone purposefully accessed tax information illegally.

Not everyone who inappropriately views tax information is a master criminal. For example, the inspector general reported to Congress last year that an IRS employee in Ohio was prosecuted after she allegedly improperly accessed her ex-husband's tax return to try to increase his child-support payment.

Q. When did presidents and presidential candidates start voluntarily releasing their tax returns?

A. It all started with Richard Nixon.

Running as Dwight Eisenhower's vice-president in 1952, Nixon got in trouble for maintaining a secret campaign fund. Eisenhower and other candidates released their full returns that year in a bid for transparency after the ensuing scandal — though Nixon, ironically, did not.

The former president faced a day of reckoning, though. In 1973, information from his tax returns was leaked by an IRS employee to the Providence Journal-Bulletin. The next year, the agency figured out the identity of the leaker, who "quit under a threat of being fired," as The Post put it at the time. No one was ever prosecuted for the Nixon leak, tax historian Thorndike said.

But the leak changed history. Since then, every major-party nominee for president has released at least a year's worth of tax returns except for Ford, who released only summaries. And every president since Jimmy Carter has released his returns while in office.

Q. How come tax returns aren't public information? Were they ever?

A. In the old days, these records were not even considered private. After Congress enacted the income tax in 1862, they were public records open to inspection by anyone who asked. Tax information became confidential shortly afterwards. For a brief window in the 1920s, newspapers published "tax lists" — information about how much (or little) muckety-mucks paid.

But tax records have been protected from disclosure since then on the belief that confidentiality encourages people to pay up.