California Code, Revenue and Taxation Code - RTC § 19301

(a) If the Franchise Tax Board or the board, as the case may be, finds that there has been an overpayment of any liability imposed under Part 10 (commencing with Section 17001), Part 11 (commencing with Section 23001), or this part by a taxpayer for any year for any reason, the amount of the overpayment may be credited against any amount then due from the taxpayer and the balance shall be refunded to the taxpayer.

(b) In the case of a joint return filed under Section 18521, the amount of the overpayment may be credited against the amount then due from both taxpayers and the balance shall be refunded to both taxpayers in the names under which the return was paid.

(c) In the case of a corporation, the balance shall be refunded to the taxpayer or its successor through reorganization, merger, or consolidation, or to its shareholders upon dissolution.