WASHINGTON ― The Internal Revenue Service has until 5 p.m. Tuesday to hand over copies of President Donald Trump’s tax returns or else face a legal battle.

Congressional Democrats set the deadline earlier this month after the Trump administration said it needed more time to respond to their original request for six years of Trump’s personal and business returns.

Federal law gives the chairs of certain congressional committees the power to look at anyone’s taxes. Trump is the first modern president to refuse to disclose any tax information, falsely claiming that he can’t because he’s under audit.

The IRS automatically audits the president and vice president every year, which didn’t stop previous presidents from releasing their returns. Democrats asked for Trump’s tax info saying they needed to examine the scope of the audits.

House Ways and Means Committee chair Richard Neal (D-Mass.) told the IRS in a letter that if it fails to comply by 5 p.m. Tuesday, “your failure will be interpreted as a denial of my request.”

The IRS and the Treasury Department, which oversees the IRS, have suggested they won’t comply with the law, which says the Treasury “shall” hand over any tax returns that the Ways and Means Committee wants. Neal said the law is “unambiguous and raises no complicated legal issues.” Experts have said they’re unaware of any previous instance of the IRS defying a disclosure request.

Trump, for his part, said earlier this month that “there is no law.” The tax disclosure law has been on the books since 1924.

A Democratic aide said that if the request is denied, Democrats will probably issue a subpoena for the documents and then sue in federal court to enforce the subpoena if needed.

It would be one of several subpoenas from congressional Democrats conducting oversight of the Trump administration. Last week, House Judiciary Committee chair Jerry Nadler (D-N.Y.) subpoenaed the Justice Department for the unredacted special counsel report on Russian interference in the 2016 presidential election and the president’s alleged efforts to obstruct the special counsel’s investigation.

The Supreme Court has repeatedly upheld congressional authority to investigate the executive branch, but at the very least, the Trump administration can use federal courts to stall the investigations.

Treasury Secretary Steve Mnuchin said the Trump tax request could set a precedent that potentially exposes all Americans to “politically-motivated disclosures of personal tax information.”

The IRS did not respond to a request for comment.