A redacted letter from HSBC to a customer with accounts at HSBC's private bank in Geneva, Switzerland is raising new concerns about financial institutions turning over offshore accountholder information to the Internal Revenue Service (IRS).

Bradley Birkenfeld is a whistleblower. In 2007, he began providing information to the United States government about activities that were going on at UBS AG. Birkenfeld provided documents, testimony and other information to U.S. authorities demonstrating that UBS AG was using the strict banking privacy laws in Switzerland to help U.S. citizens hide funds in offshore accounts and evade their tax obligations in the United States.

HSBC has been in trouble with the U.S. government in the past for the unlawful behavior of its private bank. In 2012, HSBC was fined for its role in facilitating money laundering.  Yahoo is now reporting on leaked documents from HSBC showing how involved the bank was not just in money laundering but also in helping people worldwide evade their income tax obligations.

Investors who used offshore accounts to hide money from the IRS are facing increased risks as the federal government launches new investigations into UBS and other offshore banks.  When banks and bankers make deals with the Department of Justice and with the Internal Revenue Service, these deals often involve turning over client information to the federal authorities.

Switzerland recently authorized its banks to hand over the names of professional employees, external wealth mangers, lawyers and trustees who have helped U.S. taxpayers commit tax evasion. Moreover, the banks are authorized to release email traffic in connection with U.S. taxpayers who are suspected of maintaining an undisclosed offshore account. The release of such information will likely contribute to establishing cases against those U.S. taxpayers currently under investigation. While U.S. client data is not being released at this moment, the employee information will help the IRS in its investigations into both foreign banks and U.S. taxpayers with undisclosed offshore accounts.