The Internal Revenue Service said on Wednesday that Steven Miller will become acting head of the tax agency after Doug Shulman, the present commissioner, steps down on November 9.
Shulman had been expected to resign at the end of his term in early November as head of the 104,000-employee agency that each year collects trillions of dollars in federal tax revenue and enforces the nation's complex tax laws.
Miller, IRS deputy commissioner for services and enforcement since September 2009, is a 25-year veteran of the agency.
The IRS leadership change comes ahead of a turbulent period, with Congress facing several major decisions on taxes as part of the "fiscal cliff" events at year-end. Tax experts have said that delays in issuing tax refunds could result next year.
Miller's top challenge will be "navigating next year's filing season," said Kevin Brown, a principal at Big Four accounting firm PricewaterhouseCoopers LLP who was an IRS acting commissioner for several months in 2007.
"This is the worst set of circumstances that I can remember with the 'fiscal cliff' looming," Brown said, but added that with Miller on the job, "the IRS is in very good hands."
The commissioner's post is a presidential appointment subject to Senate confirmation.
Shulman, a Democrat appointed to the post under Republican President George W. Bush, has served since March 2008. The IRS did not provide details about Shulman's next career move.
Before Shulman was confirmed by the Senate at the start of his term, the IRS was led by two acting commissioners over a transition period of more than nine months.
The previous Senate-confirmed commissioner was Mark Everson, who stepped down in May 2007.
Treasury Secretary Tim Geithner praised Miller as a "dedicated career public servant." The Treasury Department oversees the IRS.
Treasury and IRS did not say when a nominee for commissioner would be announced. That decision hinges on the outcome of the November 6 presidential election.
(Reporting by Patrick Temple-West; editing by Kevin Drawbaugh, Sandra Maler and Gary Crosse)