The Internal Revenue Service will begin laying off approximately 6,000 employees on Thursday as part of the Trump administration’s efforts to reduce the size of the federal workforce, according to three individuals familiar with the agency’s plans.

The layoffs will primarily affect more recent hires at the IRS, which the Biden administration had sought to strengthen with additional funding and new staff, the sources said, speaking on the condition of anonymity due to the sensitivity of the matter.

In recent days, the Trump administration has started laying off probationary employees, who have less job protection than their tenured counterparts, across various federal agencies, The New York Times reported on Wednesday. IRS managers informed employees on Wednesday to report to the office in the coming days and bring their government-issued equipment, according to messages obtained by The New York Times. The IRS employs approximately 100,000 accountants, lawyers, and other staff across the nation.

“Under an executive order, I.R.S. has been directed to terminate probationary employees who were not deemed critical to filing season,” one such email reads. “We don’t have many details that we are permitted to share, but this is all tied to compliance with the executive order.”

The layoffs occur amid the busy tax filing season, though again, those being dismissed were hired recently under Biden. Former IRS officials and Democrats have raised concerns that the loss of such a large number of employees could disrupt the process for millions of Americans attempting to file their taxes this year, even though the layoffs are not expected to impact those considered “critical.”

Republicans have long advocated for cuts at the IRS, accusing the agency of politically motivated actions against conservatives. Some lawmakers, including President Trump’s nominee to head the agency, have even called for abolishing the tax collector.

Trump selected Billy Long, a former Republican congressman, to lead the IRS, making the unusual move of replacing the former commissioner, Daniel Werfel. Trump has already implemented an extended hiring freeze at the IRS, and the Department of Homeland Security has requested IRS agents to assist with immigration enforcement efforts, The Times reported.