Trump Tower fell in value by an estimated A$52m last year as the rise of e-commerce ate into the worth of properties in previously lucrative shopping areas.
And another of his vast properties at 6 East 57th Street is facing the gloomy prospect of long-term tenant Nike moving out in the next few months.
The former reality star started out working for his real estate mogul father, Fred, before becoming the first billionaire president in history in January 2017. His two eldest sons, Donald Jr and Eric, are running his business while he is in office.
But there have long been questions over whether Trump is as rich and successful as he claims to be.
In 2015, the then Republican presidential candidate unveiled documents setting his personal fortune at more than A$13.5b, with an annual income of more than A$491m.
The businessman filed a financial disclosure with federal regulators but did not release the form publicly, and there was little information available on how he had calculated the figure.
Trump, for example, valued his personal brand and marketing deals at A$4.4b when he announced his candidacy, while Forbes valued his brand at just A$169m.
His campaign team said the federal forms are "not designed for a man of Mr Trump's massive wealth."
Among his sources of income were A$290m in payments from NBC related to his TV show, The Apprentice.
The A$13.5b figure he cited was up nearly 15 per cent on the previous year, apparently making him the wealthiest person to run for president.
The sum surpassed previous rich candidates including business magnate Ross Perot, heir Steve Forbes and private-equity investor Mitt Romney, the 2012 GOP nominee.
"I have a Gucci store worth more than Romney," Trump told the Des Moines Register, referring to the fashion company's flagship store in New York's Trump Tower.
It's not the only time he has boasted about his finances. In March 2011, Trump told ABC's Good Morning America: "Part of the beauty of me is that I am very rich."
That same month, he announced on Fox and Friends: "I dealt with [former Libyan leader Muammar] Qaddafi. I rented him a piece of land. He paid me more for one night than the land was worth for two years, and then I didn't let him use the land. That's what we should be doing. I don't want to use the word 'screwed', but I screwed him. That's what we should be doing."
The President does not appreciate suggestions he may not be as ludicrously wealthy as he claims. In 2009, he sued author Timothy O'Brien for defamation after O'Brien wrote that Trump's net worth might be as low as A$203m. The business mogul lost the lawsuit and an appeal.
The appeals panel noted that Trump has confessed that his public disclosures of his wealth depended partly on his mood.
"Even my own feelings affect my value to myself," he said.
