The US tax agency has awarded a former Swiss banker 104 million dollars (£65 million) for providing information about overseas tax cheats - the largest amount awarded by the Internal Revenue Service, lawyers for the whistleblower say.
Bradley Birkenfeld is credited with exposing widespread tax evasion at Swiss bank UBS AG.
Birkenfeld himself served about two-and-a-half years in prison for a fraud conspiracy conviction related to the case, which resulted in a 780 million dollars (£485 million) fine against the bank and an unprecedented agreement requiring UBS to turn over thousands of names of suspected American tax dodgers to the IRS.
"The IRS today sent 104 million messages to whistleblowers around the world - that there is now a safe and secure way to report tax fraud and that the IRS is now paying awards," Birkenfeld's lawyers, Stephen M Kohn and Dean A Zerbe, said in a statement.
"The IRS also sent 104 million messages to banks around the world - stop enabling tax cheats or you will get caught."
The IRS, which does not usually confirm individual award payments, said Birkenfeld signed a disclosure waiver, allowing the agency to confirm his award.
Birkenfeld has become something of a cause celebre among whistleblowers because of the magnitude of his case and the fact that he was jailed after co-operating with authorities. Federal prosecutors had said Birkenfeld withheld information about his own dealings with a former UBS client who pleaded guilty in 2007 to tax charges.
"The comprehensive information provided by the whistleblower was exceptional in both its breadth and depth," the IRS said in a summary of the award provided by Birkenfeld's lawyers.