Former UBS (NYSE: UBS) employee Bradley Birkenfeld, in what is reportedly the largest-ever settlement for a U.S. whistle-blower, has been awarded $104 million for his role in revealing a massive tax fraud conspiracy at the Swiss-based bank.

Having detailed how UBS went about recruiting U.S. clients, managing billions of their assets, and helping illegally shield their assets from the IRS, Birkenfeld, 47, went to prison in 2010 after pleading guilty to conspiracy. He was released on Aug. 1.

The $104 million award is the largest yet to come from the IRS whistle-blower program, designed to incentivize tipsters to report tax dodging. Taxpayers underpay by $385 billion annually, the IRS claims.

UBS was not prosecuted for its role, opting instead to pay a $780 million fine, admit to wrongdoing, and hand over data on more than 4,000 user accounts.

Another former banker at both UBS and rival Swiss bank Credit Suisse (NYSE: CS), Christos Bagios, was banned from leaving the U.S. on Saturday to visit his family in Europe. He is charged with helping American clients hide as much as $500 million from the IRS while at UBS.