Bradley Birkenfeld

The IRS has seen a surge in tax informants since a law was passed in 2006 offering a potential reward of 15% to 30% of the money collected in excess of $2 million. Delinquent taxpayers: Watch out!

The IRS' amnesty program, which ends Sept. 23, has helped the agency identify about 10 Swiss and European banks being used by U.S. citizens for offshore accounts. This does not necessarily mean that the banks are helping their U.S. account holders to evade taxes, but it gives the IRS new places to...