Internal Revenue Service union leaders said Tuesday that they expect worker absences to surge as part of a coordinated protest that could hamper the government’s ability to process tax refunds on time. Hundreds of IRS employees have received permission to skip work during the partial government shutdown due to financial hardship. The Trump administration last week ordered at least 30,000 IRS workers back to their offices, where they have been working to process refunds without pay. But IRS employees across the country—some in coordinated protest, others out of financial necessity—won’t be coming into work, according to Tony Reardon, president of the National Treasury Employees Union, and several local union officials, The Washington Post reports.

The move signals the potential for civil servants to take action that could slow or cripple government functions as the shutdown’s political stalemate continues. “They are definitely angry that they’re not getting paid...” said Reardon, whose union represents 150,000 employees at 33 federal agencies and departments. “... These employees live paycheck to paycheck, and they can’t scrape up the dollars to get to work or pay for child care.”