Rev. & Tax. Code, § 41100

(a) If the department determines that any amount, penalty, or interest has been paid more than once or has been erroneously or illegally collected or computed, the department shall set forth that fact in the records of the department, certify the amount collected in excess of the amount legally due and the person from whom it was collected or by whom paid, and credit the excess amount collected or paid on any amounts then due and payable from the person from whom the excess amount was collected or by whom it was paid under this part, and the balance shall be refunded to the person, or their successors, administrators, or executors. Any determination by the department pursuant to this section with respect to an amount in excess of fifty thousand dollars ($50,000) shall be available as a public record for at least 10 days after the effective date of that determination.

(b) Any overpayment of a surcharge by a service user to a service supplier or by a prepaid consumer to a seller who is required to collect the surcharge shall be credited or refunded by the state to the service user. However, if the service supplier or seller has paid the amount to the department and establishes to the satisfaction of the department that it has not collected the amount from the service user or has refunded the amount to the service user, the overpayment may be credited or refunded by the state to the service supplier.