The official did not say when the extension was filed or the reason cited.
The President has refused to release his previous returns because he has said he is under audit.
The returns are the subject of much speculation, as they would provide insight into Trump's financial ties and potential conflicts of interest. Trump is the first president in decades to not release his tax returns.
In an interview with The Economist
last month, Mr. Trump was asked: "If you do need Democratic support for your tax plan, your ideal tax plan, and the price of that the Democrats say is for you to release your tax returns, would you do that?"
"I don't know. That's a very interesting question. I doubt it. I doubt it. Because they're not going to ... nobody cares about my tax return except for the reporters," he said.
He added, "Oh, at some point I'll release them. Maybe I'll release them after I'm finished because I'm very proud of them actually. I did a good job."
At that point White House Director of Strategic Communications Hope Hicks interjected in the interview, saying he'd do so once the audit is over.
Treasury Secretary Steven Mnuchin took a blunter approach when referencing Trump's intent to release his returns, telling reporters
at a White House press briefing in April, "The president has no intention -- the President has released plenty of information and I think has given more financial disclosure than anybody else."
Back in May
, lawyers for the President released a letter asserting that the past 10 years of Trump's federal tax returns "with a few exceptions" don't show any income from Russian sources.
The letter also asserted that the returns show no debt owed to or interest paid to Russian lenders by Trump or his business entities.
In addition, the returns show no Russian investments in Trump's businesses or any investment by Trump or the entities he controls in Russian businesses, the lawyers said.
Nevertheless, CNN couldn't independently confirm anything in the letter because of Trump's refusal to release any of his tax returns. An outside tax lawyer who reviewed the letter concluded it is "unhelpful" if the goal is to fully gauge any potential Russian entanglements the President may have.
In March, MSNBC
obtained two pages of Trump's IRS 1040 form that showed in 2005, Trump paid $38 million in federal income taxes on a reported income of $150 million. They are the only pages of Trump's returns that have been obtained publicly.
If Maddow's report did anything to advance serious inquiry into Trump's taxes, it was by forcing the White House to demonstrate that it could disclose the president's tax information, despite his refusal to do so on the grounds that he is under audit.