Higher audit rates are designed in part to build public confidence in the tax system and encourage voluntary compliance by making taxpayers at all income levels think they may be audited, Clarke said.
'Fair Share'
"The government has an obligation and a duty to make people believe that everybody is paying their fair share," he said. "And particularly with respect to the wealthy, there's a view that they're able to get out of their obligations."
The data released today also show that tax collections haven't yet rebounded to their pre-recession levels. IRS gross collections in fiscal 2010 were $2.35 trillion, down 0.01% from the previous year. Gross collections peaked at $2.75 trillion in 2008, and the 2010 total is the lowest since 2005.
Because of flat collections and an increasing budget, the IRS's cost of collecting $100 increased to 53 cents, up from 50 cents in 2009. That's the highest level since 1995.
The IRS initiated 4,706 criminal investigations in 2010, up 14.2% from 2009. Referrals for prosecution also increased to 3,034 from 2,570, or 18.1%. The IRS audited 1,581,394 individual income tax returns in fiscal 2010.