At least 3,700 Recovery Act contract and grant recipients that received $24 billion are estimated to owe more than $750 million in known unpaid federal taxes as of September 30, 2009, GAO has said.
It said that represented nearly 5 percent of the approximately 80,000 contractors and grant recipients in the data from www.Recovery.gov as of July 2010 that it reviewed.
The Recovery Act allotted about $275 billion to be distributed through federal contracts, grants and loans — and as of March 2011, $191 billion had been paid out, according to GAO-11-485.
It said even more could be owed since IRS databases do not include amounts owed by recipients who have not filed tax returns or understated their taxable income.

