Trump paid tax in 2005 under scheme he has since vowed to abolish
President Donald Trump earned $153 million (£123m) and paid $36.5m in income taxes in 2005, according to newly disclosed tax documents.
They show the billionaire paid a rate that was effectively just under 25 per cent thanks to a tax he has since sought to eliminate.
The pages from Mr Trump's federal tax return show the then-real estate mogul also reported a business loss of $103m in 2005, although the documents do not provide details.
The forms show Mr Trump paid an effective tax rate of 24.5 per cent, a figure well above the roughly 10 per cent the average American taxpayer hands over each year.
But it is below the 27.4 per cent that taxpayers earning $1m a year average, according to data from the Congressional Joint Committee on Taxation.
The form were obtained by journalist David Cay Johnston, who runs a website called DCReport.org, and reported on MSNBC's The Rachel Maddow Show.
Mr Johnston, who has long reported on tax issues, said he received the documents in the post, unsolicited.
Mr Trump said on Twitter early on Wednesday: "Does anybody really believe that a reporter, who nobody ever heard of, 'went to his mailbox' and found my tax returns? @NBCNews FAKE NEWS!"
Mr Johnston, speaking to ABC's Good Morning America, said it is entirely possible that he received the returns from Mr Trump himself or someone close to him, saying: "Donald has a long history of leaking things about himself."
He noted that the real question remains the sources of Mr Trump's income, saying Mr Trump does not want us to know "who he's beholden to".
Mr Trump's hefty business loss appears to be a continued benefit from his use of a tax loophole in the 1990s, which allowed him to deduct previous losses in future years.
In 1995, he reported a loss of more than $900m, largely as a result of financial turmoil at his casinos.
Tax records obtained by The New York Times last year showed the losses were so large they could have allowed Mr Trump to avoid paying taxes for up to 18 years.
But his 2005 filing shows another tax prevented him from realising the full benefit of those deductions.
The bulk of Mr Trump's tax bill that year was due to the Alternative Minimum Tax, a tax aimed at preventing high-income earners from paying minimal taxes.
The AMT requires many taxpayers to calculate their taxes twice - once under the rules for regular income tax and then again under AMT - and then pay the higher amount.
Critics say the tax has ensnared more middle-class people than intended, raising what they owe the government each year.
Were it not for the AMT, Mr Trump would have avoided all but a few million dollars of his 2005 tax bill.
His campaign website called for the end of the AMT, which is expected to bring in more than $350 billion in revenues from 2016 to 2025.
As a candidate and as president, Mr Trump has refused to release his tax returns, breaking a decades-long tradition.
Although he initially promised to do so, he later claimed he was under audit by the Internal Revenue Service and said his lawyers had advised against it.
The White House hit back even before the release of the documents on Tuesday night, saying that publishing the information was illegal.
"You know you are desperate for ratings when you are willing to violate the law to push a story about two pages of tax returns from over a decade ago," the White House said.
The unauthorised release or publishing of federal tax returns is a criminal offence, punishable by a fine of up to $5,000 and up to five years in jail.
But Ms Maddow argued that MSNBC was exercising its First Amendment right to publish information in the public interest.
Mr Trump insists the American public is not interested in his returns and says little could be learned from them.
The issue was a major point of attack from his election rival Hillary Clinton, who suggested Mr Trump had something to hide.
The White House has not said whether the president plans to release his returns while he is in office.
More than a million people have signed a White House petition urging Mr Trump to release them.