It's a scoop in anybody's book. Here's what The New York Times revealed:
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"Donald J. Trump paid $750 in federal income taxes the year he won the presidency. 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."
And it alleges that Mr Trump's private wealth (or lack of it because of his high debts) is very different from his golden public image as a very successful businessman.
As the paper puts it: "As the president wages a re-election campaign that polls say he is in danger of losing, his finances are under stress, beset by losses and hundreds of millions of dollars in debt coming due that he has personally guaranteed."
What has Mr Trump said?
Not much in detail. He called the revelations "fake news" but has not denied the accuracy of the report beyond that.
"Actually I paid the tax, and you'll see them as soon as my tax returns are done," he told reporters on Sunday. "It's under audit. They've been under audit for a long time. The IRS (Internal Revenue Service - the equivalent of the ATO) does not treat me well."
How can a billionaire not pay tax?
The tax in question is on income. If Mr Trump's wealth is largely in property and, moreover, in property which makes a loss (as The New York Times indicates some of his golf courses do), income tax can be minimised.
On top of that, the paper says that he claims a lot of spending as business expense and that can be offset against tax.
He lives in his businesses, for example, whether it's his private Mar-a-Lago club in Florida or within one of the Trump hotels.
Mr Trump owns 200 acres in upstate New York. The president's family uses it as "a retreat" but The New York Times says "Mr Trump has classified the estate as an investment property, distinct from a personal residence".
"As a result, he has been able to write off $2.2 million in property taxes since 2014 - even as his 2017 tax law has limited individuals to writing off only $10,000 in property taxes a year."
"Even while declaring losses, he has managed to enjoy a lavish lifestyle by taking tax deductions on what most people would consider personal expenses, including residences, aircraft and $70,000 in hairstyling for television."
Members of his family receive fees as "consultants".
Is it legal?
Mr Trump is accused of tax avoidance which is the legal minimisation of taxes. It may need creative accountants who know every loophole and clause but it is legal - assuming he has told the tax authorities the truth (and the paper does not allege that he has not done so).
But it still may be a big problem.
According to the paper, one of the reasons for Mr Trump's low tax bill is that he received a tax refund of $72.9 million.
He justified it to the authorities by saying he had suffered a very big financial loss, possibly through the failure of one of the casinos he owned in Atlantic City.
Here's how The New York Times puts it: "But the real story may be different from the one he told.
"Federal law holds that investors can claim a total loss on an investment, as Mr Trump did, only if they receive nothing in return. Mr Trump did appear to receive something in return: five per cent of the new casino company that formed when he renounced his stake."
The Internal Revenue Service is going through the figures and fine print.
Why does it matter?
There is an election on November 3. At the moment, the challenger Joe Biden is ahead in the national polls. He is on around 50 per cent support from people polled while Mr Trump is on around 42 per cent.
But it's not quite as simple as that because under the American system the winning candidate needs to win in a few crucial states (like Florida, Iowa and Ohio) where Mr Biden's lead is thin.
And Hillary Clinton had a national lead in the polls back in 2016.
On top of that, Mr Trump has indicated that he might well not accept defeat, so Mr Biden would need to win big and unequivocally if there isn't to be a dispute which might well end up in a politicised Supreme Court, with a lot of division and rancour surrounding it.
Why might it not matter that much?
Mr Trump defies what we used to think of as normal politics.
He said four years ago: "I could stand in the middle of Fifth Avenue and shoot somebody and I wouldn't lose any voters".
He shocks liberal opinion but there is a core of his support which isn't shocked and which may even approve of his defiance of normal rules.
Before the last election, he was caught on tape saying that he would grab women's private parts with impunity - but he won the election.
And minimising taxes is something which is widely done and approved of, particularly by voters who loathe government.
But ....
Part of Mr Trump's appeal is as a successful businessman. He paints himself as a "can-do" deal-maker in contrast to a Washington elite that talks in grand language but which is ineffectual.
The implication of The New York Times story is that his success is not as great as it appears.
And "ordinary Joes" who pay taxes dutifully may wonder why the President doesn't.
In 2016, Mr Trump won the election as an outsider. His opponents alleged that he told untruths but many voters chose to overlook the alleged flaws.
This time, a record is there. "In 1267 days, President Trump has made 20,055 false or misleading claims," as The Washington Post put it.
If wavering voters perceive him as mishandling the pandemic, the tax revelations may push them from "maybe Biden" to "definitely Biden".
But Mr Trump may still be able to shoot someone on Fifth Avenue and not lose all his votes.