Washington (CNN) Hundreds of Internal Revenue Service workers dealing with financial hardship were given permission to miss work during the partial government shutdown, which could slow the federal government's ability to process taxpayer refunds, according to The Washington Post.

Union leaders told the newspaper they are expecting the absences to increase as part of a coordinated protest.

Last week, the Trump administration called back about 36,000 federal employees ahead of the tax filing season, bringing the total number of IRS employees working during the shutdown to about 57% of the workforce.

Many of the IRS employees who were called back are using a union contract provision that allows them to be absent from work if they suffer a "hardship" during a federal government shutdown, labor groups told the Post.

"After a month with no pay, real hardship does exist for IRS employees including not having the money needed to get back and forth to work or to pay for the child care necessary to return to work right now," Tony Reardon, president of the National Treasury Employees Union, said in a statement provided to CNN.

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