BUSINESS BRIEFING / CONSUMER CREDIT

American Express Co., the biggest U.S. credit card company by purchases, agreed to pay $500,000 in fines and $3.5 million in refunds after causing customers to incur penalties on convenience checks.

The Office of Thrift Supervision and the Federal Deposit Insurance Corp. fined two subsidiaries of the New York company $250,000 each.

The regulators said American Express sent out convenience checks that consumers could use to tap their credit card accounts, then lowered their credit limits and didn’t honor some of the checks, triggering penalties for the customers.

American Express will pay the refunds without admitting wrongdoing, according to a regulatory filing.