BOSTON ( TheStreet) -- The good news: The Internal Revenue Service extended the voluntary-disclosure deadline for Americans with bank accounts in foreign countries. The bad news: Not only high-rolling tax cheats need to worry about the government's crackdown, which strong-armed Swiss bank UBS ( UBS) to turn over 4,450 of U.S. customers' names. About 3,000 so-called offshore-banking clients have voluntarily come forward to amend their tax returns and seek reduced penalties. The amnesty program now will end Oct. 15 instead of the end of September. Switzerland is the largest offshore center, accounting for $1.8 trillion, or 28%, of money kept outside of investors' home countries last year. The U.K. is a close second, while Singapore, Hong Kong, Panama, Canada and Venezuela are gaining in popularity as alternatives to U.S. asset managers such as State Street ( STT), Fidelity Investments, Vanguard ( VTI) and JPMorgan Chase ( JPM). The U.S., whose debt has quadrupled, in part, because of bailouts of the banking, housing and car industries, loses almost $100 billion a year in income because of offshore tax dodgers. Americans may otherwise legally keep cash and investments in foreign countries. "In Texas, we have a lot of people who have timeshares in Mexico, and they have bank accounts for those timeshares' expenses," says Charles Meadows, a tax-litigation attorney for the Dallas law firm Meadows, Collier, Reed, Cousins & Blau. Average Americans like those may potentially be targets of a U.S. investigation, he says, even though people with a second home "never treated those accounts as anything other than a petty-cash fund to pay the operating expenses."