Cal. Rev. & Tax. Code § 283

Should the audit prescribed by this article indicate that a claim of exemption pursuant to subdivision (o), (p), (q) or (r) of Section 3, Article XIII of the Constitution has been improperly denied, the assessor shall be notified. Upon receipt of such notice the assessor shall make a redetermination and if he finds the claimant eligible he shall notify the claimant in the manner provided in Section 1605 of such erroneous determination, effect an amendment of the assessment roll, and if the claimant has already paid the tax he shall have 30 days from receipt of such notice in which to file claim pursuant to Article 1 (commencing with Section 5096), Chapter 5, Part 9 of this division. The notice shall advise the time in which claim may be filed.