California Code, Financial Code - FIN § 1422

For the purposes of computing the amount of interest or dividends payable with respect to an interest-bearing deposit account, a depository institution shall not delay beginning to compute interest on funds deposited by check or similar instrument to such an account beyond the date on which that depository institution receives provisional credit for the check or similar instrument. However, the payment of interest with respect to funds deposited by check or similar instrument which is returned unpaid shall not be required.