President-elect Donald Trump’s pick to lead the White House budget office, Rep. Mick Mulvaney, failed to pay more than $15,000 in state and federal employment taxes for a household employee, according to a disclosure form obtained by The Washington Post.

Mulvaney told members of the Senate Budget Committee that he believed he was up to date on all of his taxes and found out about the debt during the vetting process for his nomination. The South Carolina Republican said he paid $15,583.60 in back taxes to the federal government, but similar oversights brought down the nominations of several past nominees, including former senator Tom Daschle (D-S.D.), President Obama’s 2009 pick for secretary of health and human services.

“I have come to learn, during the confirmation review process, that I failed to apply FICA and federal and state unemployment taxes on a household employee for the years 2000-2004,” Mulvaney wrote in the disclosure.

Mulvaney’s disclosure, which came as part of the routine vetting process for all Cabinet nominees, was first reported by the New York Times.

A spokesman for the Trump transition team said Wednesday that Trump stands by Mulvaney and his nomination, explaining that the employee was hired to assist with Mulvaney’s newborn triplets.

“The fact of the matter is that nobody is more qualified and more prepared to fight to rein in Washington spending and fight for taxpayers than Mick Mulvaney,” the transition spokesman said in a statement. “Congressman Mulvaney raised the issue surrounding the care of his premature triplets immediately upon being tapped for this position, and has taken the appropriate follow-up measures. President-elect Trump fully stands behind Rep. Mulvaney and looks forward to his efforts to help make America great again.”

Tax issues are among the more common problems to emerge in vetting, causing at least three of Obama’s picks to withdraw from the confirmation process. The Trump transition team did not immediately respond to a request for comment, but Senate Democrats called on Republicans to encourage Mulvaney to follow previous custom and withdraw his name from consideration.

“We say to our colleagues on the Republican side of the aisle: What’s good for the goose is good for the gander,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said, referencing Daschle’s decision to step away from his nomination.

Daschle was one of the most prominent nominees to withdraw from a nomination in recent years. He paid about $140,000 in back taxes, interest and penalties for unreported consulting fees, a car and driver provided by a consulting firm that employed him and questionable charitable donations. Like Mulvaney, Daschle said the missed payments were an oversight. Daschle withdrew his name anyway.

A spokesman for Senate Budget Committee Republicans declined to comment on the status of Mulvaney’s nomination.

There is some precedent for Mulvaney to remain a nominee despite the tax issue. Obama’s 2009 nominee for treasury secretary, Timothy Geithner, was confirmed after it was revealed that he did not fully pay his taxes while working at the International Monetary Fund. Geithner blamed  “careless mistakes” for the underpayment and paid roughly $42,000 in back taxes and interest before he was confirmed.

Sean Sullivan contributed to this report.