(Bloomberg News) Former UBS AG banker Renzo Gadola, who aided Americans in cheating U.S. tax authorities before helping prosecutors snare other bankers, avoided prison when a judge sentenced him to five years of probation.

U.S. District Judge James Lawrence King in Miami rewarded Gadola today, citing the "extensive cooperation you have rendered to the United States." He faced from 10 to 16 months in prison.

Gadola pleaded guilty Dec. 22, admitting he serviced hundreds of secret Swiss bank accounts at UBS from 1995 to 2008 and later as an asset manager. Prosecutors sought leniency for Gadola, who helped build cases against two other bankers in the U.S. crackdown on offshore tax evasion. He will help in future grand jury probes and testify against former customers and colleagues, prosecutors wrote to the judge.

Gadola was willing to give "information and answer questions about his U.S. customers who used secret Swiss bank accounts to evade their income taxes as well as the Swiss bankers and Swiss financial advisers who aided and abetted those U.S. customers," prosecutors wrote.

Justice Department attorney Mark Daly told the judge today that a Gadola client was charged this week in a tax case still under court seal. Gadola's cooperation was extensive, Daly said.

"He went through client by client and colleague by colleague and went through their participation in tax evasion schemes," Daly said.

Expired Visa

Gadola, who was free on bail, returned yesterday from Switzerland to Miami, where he was detained at the airport because his visa had expired, his attorney, Peter Raben, said. Immigration officials threatened not to let him into the country, Raben said.

"I thought it was a bit ironic that he had to convince the U.S. that he had to come here and be sentenced," Raben said. As part of his probation, Gadola must return to the U.S. at least once a year, King ordered.

The case has changed Gadola's life forever, Raben said.

"He was an honored citizen and banker in Switzerland," Raben said. "That's gone."