Swiss bank UBS says customers may withdraw 15-40 billion Swiss francs ($15-41 billion) because of revised tax treaties between Switzerland and other European countries.
UBS says customers from Germany, France, Italy, Austria and Britain made net withdrawals worth 20 billion francs over the past years.
The bank said Tuesday that "15-40 billion francs are still at risk as a result of changes in the tax regulations."
Deposits at UBS and rival Credit Suisse Group have long been a target of foreign governments eager to track down untaxed assets belonging to their citizens.
Bern has recently signed treaties with France, Britain, the United States and others aimed at helping those countries obtain information on suspected tax cheats.