Francesca Foster, 32, of Milwaukee, and Rosetta Buchanan, 35, of Chicago, were arrested Thursday after police in Highland, Ind., pulled over a car driven by Buchanan for suspicion of drunken driving.
Police say a search of the car turned up 100 debit cards in the names of others, new credit cards and client records from an H&R Block in East Chicago, Ind., where customers have reported being the victims of identity theft. Foster worked for that office last year.
Court documents say IRS officials have also found more than 60 fraudulent federal and Indiana state tax refunds for 2009.
Both Foster and Buchanan were in federal custody pending a Wednesday detention hearing. Court records didn't list any defense attorneys for them on Tuesday.
The Associated Press contributed to this report.