Meanwhile, some banks aren't taking U.S. clients because they don't want to comply with a rule being developed that would require overseas financial institutions to report the identities of such customers to the IRS.
"You have a whole host of banks throughout Europe who are kicking out taxpayers," Packman said in a telephone interview. "You have nowhere to hide. Even people in compliance outside the U.S. are having trouble keeping their accounts open."
Complex Rule
Toronto-Dominion Bank of Canada, Allianz SE of Germany and Aegon NV of the Netherlands have criticized the reporting rule as too complex.
The IRS doesn't have an estimate of assets U.S. citizens hold offshore, Shulman said. Still, the $4.4 billion in penalties amassed under the programs so far is unlikely to plug the gap between the amount of taxes owed by U.S. citizens and the amount the IRS collects. The agency said Jan. 6 that U.S. companies and individuals didn't pay $385 billion in taxes owed in 2006, an increase from $290 billion five years earlier.
Unlike in the previous programs, the IRS this time isn't specifying a deadline for disclosing assets. It said the program will remain open "for an indefinite period."
The agency raised the penalty to 27.5 percent from 25 percent in 2011 and 20 percent in 2009. Taxpayers disclosing smaller accounts could pay reduced penalties of either 5 percent or 12.5 percent.
In an attempt to encourage taxpayers to come forward soon, Shulman said the penalties might be increased further or the program ended at any point.
"It makes a lot more sense for them to come in now and get the protection of not being prosecuted criminally," Shulman said. "If we catch them involuntarily, it's going to be much worse for the taxpayer."