The Treasury Department released a revised shutdown contingency plan on Tuesday calling for more than 46,000 Internal Revenue Service employees to return to work to get ready for tax filing season, but the majority of them will be unpaid until the partial government shutdown ends.

Under the previous contingency plan that has been in place since the shutdown began on Dec. 22, 88 percent of the IRS’s 80,000 employees had been sent home without pay. Under the new filing season plan released Tuesday, 46,052 employees will be back on the job starting this week; 42.6 percent of the workforce will remain furloughed.

Last week, the IRS announced that tax refunds would be processed as usual once tax season begins on Jan. 28, even if the shutdown lasts until then, and said it would be recalling a “significant portion” of its furloughed employees (see Tax season to start Jan. 28, IRS confirms). Since then, the IRS has brought back approximately 400 furloughed employees to process income verification forms for mortgage applications, but they are being paid out of the user fees for the applications (see IRS reopens income verification service despite shutdown).

The union representing IRS employees, the National Treasury Employees Union, is protesting the plan to call back workers without paying them. “There is no doubt the IRS needs to get ready for the 2019 filing season that starts Jan. 28, and IRS employees want to work,” said NTEU national president Tony Reardon in a statement. “But the hard, cold reality is that they’ve already missed a paycheck and soon they’ll be asked to work for free for as long as the shutdown lasts.”

The NTEU filed a lawsuit last week challenging the Trump administration’s plans, saying that the executive branch can’t continue to force more and more employees to show up in exchange for just an IOU. The lawsuit alleges that the Antideficiency Act violates the Appropriations Clause of the Constitution, which does not allow the government to obligate funds that have not been appropriated by Congress. A federal judge on Tuesday denied the NTEU’s request for an immediate temporary restraining order. The next hearing in the case is scheduled for Jan. 31.

“While we are disappointed that the judge did not take immediate action, we look forward to continuing our argument that the administration cannot require more and more employees to report to work without pay,” Reardon said. “This shutdown cannot go on. The government has important services to deliver and it needs its full workforce back on the job, with pay, as soon as possible.”