Cal. Rev. & Tax. Code § 6901

(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 and shall certify the amount collected in excess of the amount legally due and the person from whom it was collected or by whom paid. The excess amount collected or paid shall be credited by the department 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 the person’s successors, administrators, or executors, if a determination by the department is made in any of the following cases:
1. (1) Any amount of tax, interest, or penalty was not required to be paid.
2. (2) Any amount of prepayment of sales tax, interest, or penalty paid pursuant to Article 1.5 (commencing with Section 6480) of Chapter 5 was not required to be paid.
3. (3) Any amount that is approved as a settlement pursuant to Section 7093.5.
(b) Any overpayment of the use tax by a purchaser to a retailer who is required to collect the tax and who gives the purchaser a receipt therefor pursuant to Article 1 (commencing with Section 6201) of Chapter 3 shall be credited or refunded by the state to the purchaser. 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.