The ID-theft sweep led to 734 law enforcement actions, including indictments, complaints and arrests, the IRS said in a statement Thursday.
The sweep is part of a new crackdown on the crime to better help protect taxpayers and victims, the IRS said.
Prison time has increased for identity thieves. The average sentence in fiscal year 2012 was 48 months, a four-month increase from 2011.
Law enforcement actions against the crime has also increased, with 2,400 actions against 1,310 suspects in fiscal year 2012, compared to 1,703 actions against 907 in just the first four months of fiscal year 2013, the IRS said.
"As tax season begins this year, we want to be clear that there is a heavy price to pay for perpetrators of refund fraud and identity theft," said IRS Acting Commissioner Steven T. Miller. "We have aggressively stepped up our efforts to pursue and prevent refund fraud and identity theft, and we will continue to intensely focus on this area. This is part of a much wider effort under way for the 2013 tax season to stop fraud."