Tax preparers need to step up security in the face of a new scam that thieves are carrying out, the IRS warned in a memo issued Tuesday.

These criminals have a new twist on an old scam, the IRS said. The thieves steal client data from tax professionals and then file fraudulent tax returns. The criminals deposit the tax refund in a real bank account digitally or send the taxpayer a check. Thieves are then using various tactics to reclaim the refund from the taxpayers.

In one version of the scam, criminals posing as debt collection agency officials acting on behalf of the IRS contact the taxpayer to say a refund was deposited in error, and they ask the taxpayer to forward the money to their collection agency.

In another version, the taxpayer who received the erroneous refund gets an automated call with a recorded voice saying he is from the IRS and threatens the taxpayer with criminal fraud charges, an arrest warrant and a “blacklisting” of their Social Security number. The recorded voice gives the taxpayer a case number and a telephone number to call to return the refund.

The IRS is asking tax professionals to step up security to protect clients’ sensitive tax and financial files.

Taxpayers receiving erroneous refunds should contact their tax preparers immediately and talk with their bank to see if account changes need to be made.

Sometimes a taxpayer filing a return electronically will find the return rejected because a return under that Social Security number has already been filed. The IRS publishes guidelines for reporting identity theft, Taxpayer Guide to Identity Theft, and for returning bogus refunds, Tax Topic Number 161.