Informing Other Bank About Bounced Check

"A" deposits a check from individual "B" in his account. The check bounces. Both banks are located and do business in Los Angeles county. How long (or how many days) the bank has to inform "A"? - Please include the code / regulation reference. - I understand that depending on different factors it could take from couple of hours up to 2 business days (for the bank) to find out that a check has bounced .... the question is when the bank finds out (a) the bank is obliged to inform A and (b) within xx number of days.