The IRS rehired hundreds of former staffers with conduct issues, even bringing ex-employees with tax issues back into the fold, a new federal audit has found.

Treasury’s inspector general for tax administration said that the IRS generally followed the federal guidelines, which take into account whether a potential employee has a criminal record or failed a drug test, when bringing back former staffers.

But other staffers rehired had documented conduct issues from previous tenures at the IRS, including purposefully not filing their taxes, wrongly authorizing taxpayer information and lying on official forms. Of those rehired, roughly one in five then went on to have further performance problems.

“Based on the types of prior performance and conduct issues we identified, rehiring certain employees presents increased risk to the IRS and taxpayers,” J. Russell George, the tax administration inspector general, said in a statement.