From Reuters.com:
 
The percentage of corporate tax returns  audited by U.S. collectors fell about 9 percent in 2008 and was down  nearly 20 percent from about a decade earlier, an inspector general  report released on Monday said.
About 15.3 percent of returns filed by  corporations with $10 million or more in assets were examined by the  Internal Revenue Service last fiscal year, down from about 16.8 percent  in 2007, the Inspector General for Tax Administration for the U.S. Treasury  Department said in its annual report.
In 1999, about 19 percent of tax returns  for the group were examined by tax collectors. The rate of examination  ranged between 15 and 19 percent in the intervening years, with the  exception of a 20 percent rate in 2005.
The IRS's enforcement staff has been  whittled down in recent years, a response to fervent complaints by some  U.S. lawmakers critical of what was characterized as aggressive tax  collection.
"After several years of improved  results, many collection function activities and results declined during  FY 2008," the report said.
The enforcement staff shrank 20 percent  to 14,900 at the end of 2008, down from 18,700 in 1999, the report said.
 
President Barack Obama has proposed doubling  the agency's enforcement budget for 2010, including hiring about 800  new staffers just to enforce international tax law. That is part of  a wider effort by the administration to crack down on what it calls  the abusive use of tax loopholes and outright tax evasion.
 
Enforcement revenue fell in 2008, though  that interrupted a steady rise in the past decade or so, the report  said.
The IRS collected $2.75 trillion in fiscal  year 2008, a record.
The report did not make any specific  recommendations, but noted the enforcement of tax laws is among the  key "high-risk" areas consistently cited by the Government  Accountability Office.
