A retired Boeing sales manager is the latest UBS client to plead guilty to filing a false tax return after the Swiss bank agreed to disclose the identities of some of its U.S. clients.

Robert Cittadini of Bellevue, Wash., accepted responsibility for hiding up to $1.86 million in accounts at the Swiss bank and failing to report the income he earned from the accounts on his 2001 to 2003 tax returns. Cittadini also did not file a Report of Foreign Bank and Financial Accounts, or F-BAR form, for each of those years.

Cittadini initially opened an account with UBS in the early 1990s in his own name, but around 2001, Swiss banker Hansruedi Schumaker, who was indicted in August 2009 on conspiracy charges, helped him transfer assets from his UBS account to an account named for Mataropa Finance Limited, a nominee Hong Kong corporation that helped him hide the assets. Swiss lawyer Matthias Rickenbach, also indicted in August, was a director of the Hong Kong entity.

Sentencing in Cittadini’s case is scheduled for Jan. 8, 2010. He faces up to three years in prison and a $250,000 fine. He also has agreed to pay a civil F-BAR penalty based on 50 percent of the highest account balance from 2001 to 2007.

“This is a time of reckoning for those who thought they had found a safe haven for cheating,” said U.S. Attorney Jenny A. Durkan in a statement. “People who avoid paying their fair share hurt all of us who follow the law and conscientiously pay our taxes.”

In February 2009, UBS entered into a deferred prosecution agreement in which the bank admitted to helping U.S. taxpayers hide accounts from the IRS. As part of the agreement, UBS provided the U.S. government with the identities and account information of some U.S. customers of the bank’s cross-border business. Cittadini’s case is the sixth guilty plea arising from that information.

In June 2009, Steven Michael Rubinstein, a Boca Raton, Fla., accountant, pleaded guilty to filing a false tax return. In April 2009, another UBS client, Robert Moran, a Ft. Lauderdale, Fla., yacht broker, pleaded guilty to filing a false tax return. In July 2009, Jeffrey Chernick, of Stanfordville, N.Y., pleaded guilty to filing a false tax return. In August 2009, John McCarthy, a resident of Malibu, Calif., pleaded guilty to failing to report his ownership of and interest in a foreign financial account. In September 2009, Juergenn Homann of Saddle River, N.J., pleaded guilty to failure to file an F-BAR form.

Over the summer, UBS agreed to hand over information on an additional 4,450 U.S. clients under an agreement brokered by the Swiss and U.S. governments.