IRS probes offshore credit card accounts.(Knight Ridder Newspapers)

MIAMI _ In a broadening investigation of tax cheats, the Internal Revenue Service said this week that MasterCard has turned over records from more than 230,000 credit card accounts issued by offshore banks, enabling it to develop hundreds of cases for civil audits or possible criminal investigations.

Visa and American Express may not be far behind.

The investigation is part of a massive crackdown that began in October 2000 to track down taxpayers who are using offshore banks to hide assets from the U.S. tax collector. The IRS estimates there may be as many as one million to two million U.S. citizens holding debit or credit cards issued by offshore banks.

Among the people IRS investigators found using the offshore MasterCards: executives of publicly held companies, doctors, lawyers, …