US authorities are set to have the details of almost 4,500 US citizens' accounts handed over to them with 250 people suspected of tax evasion and the rest of fraud.
The UBS accounts that are being looked into are ones containing assets of at least one million Swiss Francs ($986,200) in average revenues over the past three years.
It is believed the investigation will bring in billions of previously undisclosed dollars in taxation for the US Treasury.
In addition to those under investigation, the Inland Revenue Service and the Department of Justice announced that more than 14,700 people with formerly undisclosed foreign bank accounts have come forward under their voluntary tax disclosure program.
Deputy attorney general David W Ogden said: "The message to American taxpayers is clear: the era of bank secrecy and hidden assets is over."
By Tony Aynsley