The Department of Justice on Thursday filed a lawsuit in Miami asking a federal judge to force UBS AG to disclose to the Internal Revenue Service the identities of its U.S. customers with secret Swiss accounts.

The government alleges that as many as 52,000 U.S. customers hid their UBS accounts from the IRS. Roughly 20,000 of those accounts contained securities and 32,000 contained cash, prosecutors said.

On Wednesday UBS reached a deal with federal prosecutors to avoid prosecution for helping wealthy Americans hide accounts and evade taxes.

As part of the settlement, UBS agreed to pay $780 million in penalties and restitution and promised to reveal the identities of some U.S. customers.

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