“Trump taxes show chronic losses and years of tax avoidance,”

Donald Trump, a self-proclaimed billionaire, paid only $750 in federal income taxes in the year he was elected US president, according to a stunning New York Times investigation that could shake up the presidential election.

“Trump taxes show chronic losses and years of tax avoidance,” was the banner headline on the paper’s website on Sunday. The president’s tax returns have long been the holy grail of American political reporting.

The president “paid $750 in federal income taxes the year he won the presidency”, the paper reported, adding that “in his first year in the White House, he paid another $750.

“He had paid no income taxes at all in 10 of the previous 15 years – largely because he reported losing much more money than he made.”

In all, the paper said, Trump paid no federal income taxes in 11 of 18 years its reporters examined. Many of his businesses, including his golf courses, report significant financial losses – which have helped him to lower his taxes.

The Times also said the documents it had obtained “comprise information that Mr Trump has disclosed to the IRS, not the findings of an independent financial examination. They report that Mr Trump owns hundreds of millions of dollars in valuable assets, but they do not reveal his true wealth. Nor do they reveal any previously unreported connections to Russia.”

The paper said it would not publish the documents, in order to protect its source.

At a White House press briefing on Sunday, Trump made wild allegations about plots against him and about Biden, who he will debate for the first time on Tuesday. Eventually, he dismissed the Times report as “totally fake news”.

He said: “We went through the same stories, you could have asked me the same questions four years ago, I had to litigate this and talk about it.

“Totally fake news, no. Actually I paid tax. And you’ll see that as soon as my tax returns – it’s under audit, they’ve been under audit for a long time. The [Internal Revenue Service] does not treat me well … they treat me very badly. You have people in the IRS – they treat me very badly.”

The president added: “The New York Times tried it, the same thing, they want to create a little bit of a story. They’re doing anything they can. That’s the least of it. The stories that I read are so fake, they’re so phony.”

Pressed on why a billionaire only paid a few hundred dollars in the year he won the presidency, Trump insisted: “First of all I paid a lot, and I paid a lot of state income taxes too. The New York state charges a lot and I paid a lot of money in state. It’ll all be revealed. It’s going to come out but after the audit.”

The revelations threaten to damage Trump’s repeated claim to be a successful businessman and therefore a capable steward of the US economy.

The Times also said he has used “questionable measures” to reduce his tax bill. He faced a possible hit of “more than $100m” if he lost “a decade-long audit battle with the IRS over the legitimacy of a $72.9m tax refund that he claimed, and received, after declaring huge losses”.

It promised more stories in the coming weeks, adding: “The tax returns that Mr Trump has long fought to keep private tell a story fundamentally different from the one he has sold to the American public.”

Trump will face Joe Biden at the polls on 3 November. He has long resisted demands by political opponents and the media to release decades of tax information. He is the first president since the 1970s to keep his tax returns concealed.