California Code, Revenue and Taxation Code - RTC § 19302

If the Franchise Tax Board determines that the taxpayer paid an amount not required to be paid under this part, the Franchise Tax Board shall set forth that fact in its records and may either credit the amount on any amounts then due and payable under this part from the taxpayer by whom the amount was paid or refund the amount or the balance to the taxpayer or the taxpayer's successors, administrators, or executors.