The Olenicoff case prompted the IRS to force UBS into handing over the names of 250 Americans who had secret accounts at the bank. UBS also agreed to pay a $780 million fine for encouraging its clients to evade U.S. taxes.

So far, four of the clients on the list of 250 have pled guilty to tax violations, part of what the IRS says are 150 “active investigations” of tax cheaters who stashed $100 million in secret UBS accounts. Juergen Homann, a 66-year-old New Jersey businessman, on September 25 became the latest to admit having an undisclosed UBS account and will be sentenced in January.

In addition to the four, Bradley Birkenfeld, a 44-year-old American who had worked as a banker at UBS and has been cooperating with the U.S. investigation, has also entered a guilty plea. He was sentenced in August to three years and four months in prison, along with a $30,000 fine. Also being accused of tax fraud is a senior UBS banker and a Swiss attorney who advised clients on setting up tax-shelter accounts.

Press says there seemed to be a common thread to the letters sent out recently by UBS. All were to clients who had closed their accounts in 2008 and opened new accounts at other institutions. “The UBS case is the test case for Switzerland,” Press said. “Once that’s done, it’s likely the Department of Justice will move on to Credit Suisse and other banks that may not have any U.S. presence. Then they’re planning on moving to other jurisdictions.”

According to Press, the tax-fraud cases are simple to prosecute. If the client didn’t indicate foreign earnings on their tax return and failed to file a document known as a Foreign Bank Account Reporting form, then that is sufficient evidence to be convicted.

In addition to Switzerland, prosecutors in several countries are focusing on secret accounts in the tax haven of Liechtenstein after a former employee of LGT Bank sold a CD-ROM containing thousands of account names to the German intelligence agency for a reported $7 million. The revelations have already forced the resignation of Klaus Zumwinkel, head of the German post office, whose name appeared on the list.

Now that Switzerland and Liechtenstein have started cooperating with tax authorities, some risk-seeking clients are heading to other tax havens such as Panama and Colombia. The Bahamas recently announced that it will not allow foreign governments to go “fishing” for tax dodgers at Bahamas banks.

“Some places are promoting themselves as stubbornly holding out but there is an inherent risk,” says Lewis. ‘While other jurisdictions and banks are still marketing the discreet nature of their services, I think there is now an acknowledgement that it is a risky business.”

The IRS this week disclosed that the number of Americans who have sought to earn a reward by turning in tax cheats quadrupled in the last year to 476. Whistle-blowers can earn up to 30 percent of the hidden assets that are recovered. With the coordinated international crackdown on tax cheats, there really may be few places left to hide.