Bank secrecy (or bank privacy) is a legal principle in some jurisdictions under which banks are not allowed to provide to authorities personal and account information about their customers unless certain conditions apply (for example, a criminal complaint has been filed). In some cases, additional privacy is provided to beneficial owners through the use of numbered bank accounts or otherwise. Bank secrecy is prevalent in certain countries such as Switzerland, Lebanon, Singapore and Luxembourg, as well as offshore banks and other tax havens under voluntary or statutory privacy provisions.
Created by the Swiss Banking Act of 1934, which led to the famous Swiss bank numbered account, the principle of bank secrecy is always considered one of the main aspects of private banking. It has also been accused by NGOs and governments of being one of the main instruments of underground economy and organized crime, in particular following the class action suit against the Vatican Bank in the 1990s, the Clearstream scandal and the terrorist attacks of September 11, 2001. Former bank employees from banks in Switzerland (UBS, Julius Baer) and Liechtenstein (LGT Group) have testified that their former institutions helped clients evade billions of dollars in taxes by routing money through offshore havens in the Caribbean and Switzerland. One of these, Rudolf M. Elmer, wrote, "It is a global problem...Offshore tax evasion is the biggest theft among societies and neighbor states in this world." The Swiss Parliament ratified on June 17, 2010 an agreement between the Swiss and the United States governments allowing UBS to transmit to the US authorities information concerning 4,450 American clients of UBS suspected of tax evasion.