On the first Tax Day filing deadline since President Donald Trump was elected there are still many questions about his taxes. Here are a few:

Why Hasn't Trump Released His Returns?

Trump and his surrogates on the campaign trail last year gave various reasons why Trump has not made public his returns when his opponent, Democratic candidate Hillary Clinton, had released nine years of past returns.

Trump often said his tax returns are under audit by the IRS and that's why he couldn't release them. But the IRS said an audit doesn't prevent an person from disclosing their taxes.

Trump also said during the campaign that there was nothing to learn from his returns, while his vice presidential pick, Mike Pence, called the issue a "distraction."

After Trump was elected, he and his team returned to the argument that the American people don't care about the issue. However, polls indicate that the majority of Americans are very much interested in Trump's finances, and experts say that there's plenty to be gleaned from a thorough review of the billionaire president's tax documents.

Critics have charged that he has something to hide — suggesting that Trump pays little to no taxes on his substantial income, or that he has undisclosed business interests or debts that would present a conflict of interest in executing his presidential duties.

Does Trump Pay Taxes?

Here's what we know, according to leaked Trump tax documents.

Trump paid $38 million in federal income taxes in 2005.

After MSNBC's "The Rachel Maddow Show" said it would release the details, the White House confirmed in March that Trump paid $38 million in federal income tax on more than $150 million in income for 2005.

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DCReport.org obtained two pages from what it said were Trump's 2005 Form 1040, but those pages don't reveal sources of income — just that Trump reported about $152 million in income. Those documents were released on Maddow's show.

Of the $38 million in taxes Trump paid that year, $31 million came in the form of the alternative minimum tax. As president-elect, Trump called for the elimination of the alternative minimum tax — a significant detail now that we know how his personal finances could be affected by legislation he supports as president.

In a statement, the White House said the "illegally published" tax records proved only that Trump "was one of the most successful businessmen in the world with a responsibility to his company, his family and his employees to pay no more tax than legally required."

Trump reported a $916 million loss in 1995 that experts said could have allowed him to pay no federal income taxes for up to 18 years.

Back in October, The New York Times published a report based on documents it said were Trump's 1995 state income tax returns. The documents — three pages mailed to a Times reporter — appear to show that Trump reported a $916 million loss, which, according to experts, could have allowed him to pay no federal income taxes for up to 18 years.

However, there was nothing in the report that shows he actually took advantage of the rules to avoid paying taxes. A Trump campaign statement in response to the article said: "Mr. Trump is a highly-skilled businessman who has a fiduciary responsibility to his business, his family and his employees to pay no more tax than legally required."

Trump may not have paid income taxes in 1991 or 1993.

Separate documents from the New Jersey Division of Gaming Control and the Casino Control Commission obtained by Politico appear to indicate that Trump did not pay income taxes in 1991 and 1993 because "Trump's losses were large enough to prevent him from owing taxes." Trump's campaign responded at the time to the Politico report with, "Welcome to the real estate business."

It's possible Trump did not pay income taxes in 1984.

This was revealed by two tax court cases from the early 1990s.

In 1978 and 1979, Trump may not have paid federal income taxes.

In 1981, when Trump was attempting to obtain a casino license, the state of New Jersey analyzed his finances and issued a report that cited tax payments for 1975 through 1979. Politifact found that Trump's federal tax bill for the first three of those five years was $71,932 on a reported income of $219,334 (not adjusted for inflation)." The other two years, Trump did not pay federal taxes due to losses in excess of $3 million. The returns themselves were never made public; the information comes from the casino commission report.

He told ABC News last year that his federal income tax rate was "none of your business."

RELATED: Who is leaking Trump's tax returns?

How Much Does Trump Give to Charity?

His charitable giving became a campaign issue when Washington Post reporter David Fahrenthold investigated the president's foundation and found that Trump regularly exaggerated his philanthropic activity linked to the foundation. However, little is publicly known about his personal charitable giving, although Trump, who does not accept a salary as president, recently announced he was donating the first quarter of his pay to the National Park Service.

Does Trump Have a Financial Connection to Russia?

Trump says no — "I have no dealings with Russia, I have no deals in Russia," he told reporters in January ahead of his inauguration — but some argue that the extent of his ties to Russia, if any, and to other countries can't be known without seeing his tax returns.