Cal. Rev. & Tax. Code § 531.6
The taxpayer who has filed a claim for the homeowners' exemption which has not been denied by the assessor is responsible for notifying the assessor when the property is no longer eligible for the exemption.
Upon any indication that a homeowners' exemption has been incorrectly allowed, the assessor shall make a redetermination of eligibility for the homeowners' exemption. If the assessor determines that the property is no longer eligible for the exemption, he shall immediately cancel the exemption on the property.
If a homeowners' exemption has been incorrectly allowed, an escape assessment as allowed by Section 531.1 in the amount of the exemption with interest as provided in Section 506 shall be made, except that where the exemption was allowed as the result of an assessor's error, the amount of interest shall be forgiven. If the exemption was incorrectly allowed because of erroneous or incorrect information submitted by the claimant with knowledge that such information was erroneous or incomplete or because the claimant failed to notify the assessor in a timely manner that the property was no longer eligible for the exemption, the penalty provided in Section 504 shall be added to the assessment. If the property subject to this paragraph has been transferred or conveyed to a bona fide purchaser for value during the period commencing with the lien date and ending July 1 of the fiscal year for which such exemption was incorrectly allowed, and the claimant is not the purchaser, any amount of penalty provided by Section 504 or any amount of interest provided by Section 506 imposed pursuant to the escape assessment due to such incorrect homeowners' exemption shall be forgiven.
Ca. Rev. and Tax. Code § 531.6