FORT LAUDERDALE, Fla. – A wealthy accountant who is the first U.S. citizen charged in a wide-ranging tax probe of Swiss banking giant UBS AG pleaded guilty Thursday to filing a false tax return.

Steven Michael Rubinstein pleaded guilty to filing a false tax return in 2004, the U.S. Attorney's Office reported.

Rubinstein failed to report UBS income on his returns from 2001 to 2007, the Internal Revenue Service claimed. As part of his plea agreement, Rubinstein agreed to pay a 50 percent penalty for the year with the highest balance in the account as of June 30. That was 2004.

Rubinstein's name was among roughly 300 American account holders turned over to U.S. authorities by UBS in a deal that also required the Swiss bank to pay $780 million in fines and restitution. In a separate lawsuit filed in Miami, the IRS was seeking the identities of another 52,000 UBS customers suspected of using bank secrecy to shield assets from U.S. taxes. UBS is contesting the lawsuit.

Rubinstein was accused of creating a shell corporation in the British Virgin Islands in 2001 to conceal his ownership of the UBS account, which he then used to finance construction of a multimillion-dollar Florida home, deposit some $2 million in Krugerrand gold coins and make numerous investments. In all, prosecutors said he hid some $6 million with UBS.

A message left at the office of his attorney, Robert Panoff, was not immediately returned.

Rubinstein is scheduled to be sentenced Sept. 30. He faces a maximum three years in prison. Rubinstein remains free on $12 million bail.