Some U.S. taxpayers who have been hiding their money in Swiss bank accounts might not worry about being exposed to the IRS, depending on the details of the U.S.’s recent agreement with Switzerland.

An interesting story in yesterday’s New York Times describes how the detailed criteria for which taxpayer accounts will be turned over to U.S. authorities have not yet been revealed, although a sealed document about the agreement is expected to be released by Nov. 17.

Before that happens, though, the IRS is giving taxpayers until Sept. 23 to come forward voluntarily or face stiff penalties, but some are still playing a game of cat and mouse, hoping they won’t be caught.

I talked with Paul Behling, a senior partner at the law firm Withers Bergman, a few days ago about U.S. efforts to get more people to come forward. His firm has been helping about 150 to 200 clients who have bank accounts in countries such as Switzerland, Hong Kong and Singapore deal with the tougher reporting requirements and penalties. Now Monaco has joined the list of countries that are cooperating with the U.S. on exchanging tax information (see U.S. to Get Secret Bank Account Info from Monaco).

“By various means the IRS will use its economic and political muscle to get these countries to comply,” said Behling.

He isn’t advising any of his clients to look for other tax havens where they can stash their money, but his firm does let people know about the still legitimate means for doing offshore tax planning, such as setting up offshore trusts where taxes can be deferred.

He doesn’t know what will happen after the Sept. 23 deadline passes for filing the FBAR form, and whether the IRS will extend the deadline once again. “The door may be closed,” said Behling. However, the IRS may still allow people to file amended returns or meet with their local U.S. Attorney’s office to work out a deal, or the IRS may put in place another amnesty program, perhaps with harsher penalties for those who didn’t come forward voluntarily before the 23rd.

Some people no doubt will take a chance and wait to see whether the authorities in Switzerland, Monaco or some other country forward their bank account information to the IRS. But that’s a gamble not unlike rolling the dice in Monte Carlo, and could mean jail time or harsh penalties that could effectively empty out the contents of those bank accounts that until recently seemed to be so safe.