California Code, Revenue and Taxation Code - RTC § 533

(a) If an escape assessment is made as a result of an audit that discloses that property assessed to the party audited has been incorrectly assessed either for a past tax year for which taxes have been paid and a claim for refund is not barred by Section 5097 or for any tax year for which the taxes are unpaid, the tax refunds resulting from the incorrect assessments shall be an offset against proposed tax liabilities, including accumulated penalties and interest, resulting from escaped assessments for any tax year covered by the audit.

(b) If a tax refund, authorized under this section exceeds any proposed tax liabilities, including accumulated penalties and interest, the party audited shall be notified by the tax collector of the amount of the excess and of the fact that a claim for cancellation or refund may be filed with the county as provided by Section 5096 or 5096.7.