The IRS Program on whistleblower is clear
"On December 20, 2006, the US President signed into law new legislation that dramtically strenghtens the IRS`s whistleblower program. Unter the new law, qualified whistleblowers will be enitlted to awards of up to 30 % of funds that are recovered by the IRS based on information provided by whistleblowers."
If this Program would have been applied to Mr. Bradely Birkenfield, he would have been awarded an even higher amount than the US 104 mio.
However, Rudolf Elmer expresses part of his view to the matter in Reuters.