Donald Trump has revealed in his financial disclosure that he reimbursed his personal lawyer for unspecified "expenses", with no mention of a payment to porn actress Stormy Daniels to keep quiet about a sexual tryst she said they had.
The head of the nation's ethics office questioned why Mr Trump did not include this in his previous year's sworn disclosure and passed along his concerns to federal prosecutors.
"I am providing both reports to you because you may find the disclosure relevant to any inquiry you may be pursuing," David Apol, acting director of the Office of Government Ethics (OGE), wrote to Deputy Attorney General Rod Rosenstein.
Mr Apol wrote that he considers Mr Trump's payment to Michael Cohen to be a repayment on a loan and that it was required to be included in Mr Trump's June 2017 disclosure.
Mr Trump's lawyer Rudy Giuliani told Fox News Channel's Laura Ingraham that the US president was "fully aware" of the disclosure and "endorsed the strategy".
"We wouldn't do it without him," Mr Giuliani said on The Ingraham Angle, according to an excerpt provided by the network.
"He's the client, after all, and has tremendous judgment about things like this. And I think it - that the OGE, the Office of Government Ethics, basically agreed with us that it has been fully disclosed.
But ethics experts say that if that payment was knowingly and wilfully left out, Mr Trump could be in violation of federal ethics laws.
"This is a big deal and unprecedented. No president has been previously subject to any referral by (Office of Government Ethics) to DOJ as a result of having failed to report an item on their public financial disclosure report," said Virginia Canter, a former ethics official in the Clinton and Obama White Houses who is now with the watchdog group Citizens for Responsibility and Ethics in Washington.
How Mr Trump dealt with the Daniels hush money in his disclosure has been closely watched, particularly after Mr Giuliani gave interviews earlier this month saying the president had reimbursed Mr Cohen in a series of payments after the campaign was over.
Mr Trump and Mr Giuliani have clashed over what the president knew and when he knew it.
In a footnote in tiny type on page 45 of his 92-page disclosure, Mr Trump said he reimbursed Mr Cohen for "expenses" ranging from 100,000 US dollars to 250,000 dollars.
The report said the president did not have to disclose the payment but was doing so "in the interest of transparency".
While the disclosure did not specify the purpose of the payment, Mr Cohen has said he paid 130,000 dollars to Ms Daniels in the weeks before the 2016 presidential election to keep her from going public about her allegations that she had sex with the married Mr Trump in 2006.
Ms Daniels' lawyer, Michael Avenatti, tweeted, "Mr Trump's disclosure today conclusively proves that the American people were deceived."
The tweet continued: "This was NOT an accident and it was not isolated. Cover-ups should always matter."
The Trump Organisation referred questions about the disclosure report to the president's lawyer Sheri Dillon of Morgan, Lewis & Bockius.
Ms Dillon did not immediately respond to a request for comment.
The Cohen footnote appears in a report giving the first extended look at Mr Trump's revenue from his properties since he became president.
In all, Mr Trump's vast array of assets - hotels, resorts, books, licensing deals and other business ventures - generated revenue last year of at least 453 million. The report estimated the holdings are worth at least 1.4 billion dollars.
His Washington, DC, hotel near the Oval Office, a magnet for diplomats and lobbyists, took in 40 million dollars.
His Doral golf course and resort in Miami took in 75 million dollars. His Mar-a-Lago resort in Palm Beach, Florida, received 25 million dollars, and his golf club in Bedminster, New Jersey, generated 15 million dollars.
Some of the 12-month figures for his properties are down from his previous report, but that earlier report covered about 16 months and so it is not directly comparable.
The figures are before expenses and so give no indication of how much profit the president made off the properties.
Mr Trump has at least 315 million dollars in debt, about the same as he reported a year ago. One of his biggest lenders is Ladder Capital, which has lent more than 100 million dollars.
Mr Trump owes Deutsch Bank as much as 175 million dollars.
The debt figures are given in broad ranges in the report and capped at 50 million dollars, so it is unclear just how much Mr Trump actually owes. The president's tax returns would give a clear picture, but Mr Trump has broken with tradition by refusing to make them public.
When Mr Trump took office, he refused to fully divest from his global business, another break with presidential tradition.
Instead, he put his assets in a trust controlled by his two adult sons and a senior executive. Mr Trump can take back control of the trust at any time, and he is allowed to withdraw cash from it as he pleases.
His report shows that Mr Trump received 64,840 dollars from the Screen Actors Guild pension fund. Mr Trump has appeared in several movies, including Home Alone 2 and Zoolander.
For operating New York's Wollman Rink in Central Park, the president took in 9.3 million dollars.
Though it was published three decades ago, Mr Trump's The Art Of The Deal last year generated as much as one million dollars.