The other seven were all former US clients of Switzerland’s UBS, the bank at the centre of enforcement efforts over the past year.
“The rich are not different,” Manhattan US Attorney Preet Bharara said in a statement.
“Multimillionaires with secret Swiss bank accounts have to pay their taxes just like everyone else. It is that simple.”
US officials have said they are using reams of data gathered in last year’s tax amnesty program to find suspicious patterns that could lead them to banks beyond UBS.