Here is a paragraph out of an Accuracy & Integrity Procedures that I’ve wrote.
After a completed direct dispute notice is received the bank has 30 days to complete a reasonable investigation. This includes reviewing all relevant information provided by the customer; a complete investigation of the disputes and report the results to the consumer before the 30 day expiration of the dispute (FACT ACT 15 U.S.C. 1681i(a)(1)); and if information was found to have been reported inaccurately, promptly notify each CRA to which the bank reported the inaccurate information to.