California Code, Revenue and Taxation Code - RTC § 255

(a) Affidavits required for exemptions named in this article, except the homeowners' exemption, shall be filed with the assessor between the lien date and 5 p.m. on February 15.

(b) Affidavits for the homeowners' exemption except as otherwise provided in Sections 255.1, 255.2, and 275, shall be filed with the assessor any time after the claimant becomes eligible but no later than 5 p.m. on February 15.

(c) Notwithstanding the provisions of subdivision (a), any claimant who has been found ineligible for the church exemption or the religious exemption may file an affidavit for a welfare exemption.  Affidavits for the welfare exemption filed pursuant to this subdivision shall be filed within 15 days from the date of notification by the assessor of the claimants' ineligibility for the church exemption or the religious exemption.