As part of the ongoing efforts to combat individuals hiding funds from American taxation in Swiss bank accounts, Swiss banks have been offered immunity for their involvement in hiding the funds, so long as they reveal the accounts by New Years Eve.

Seizing the opportunity, Politico reports that it has obtained letters expressing that Swiss banks are “quietly warning wealthy U.S. clients with secret accounts to come clean with the tax man in the next two weeks – or risk jail time.”

Among the banks targeted by the government’s investigations are HSBC, Credit Suisse, and Julius Baer. These institutions are suspected of providing cover for these tax evaders, in the wake of admissions from the UBS $780 million settlement in 2009.

“Tax evasion has been an issue of key interest for American regulators in the past few years,” commented James Kauffman, an attorney with the Levin, Papantonio law firm who practices with the firm’s business torts and securities department. “These recent actions are a sign that the Swiss banks are taking the offers made by the U.S. seriously.”

The threats from the government are serious. As a result of investigations and lawsuits, Wegelin & Co., the oldest Swiss bank, and the 13th oldest bank in the world, has announced that it intends to close.

Just Monday, a UBS executive that has been pursued by U.S. prosecutors for the past five years, appeared in a Florida court.

Joshua is a writer and researcher with Ring of Fire. You can follow him on Twitter @Joshual33.