Cal. Rev. & Tax. Code § 275

(a) If a claimant for the homeowners’ property tax exemption fails to file the required affidavit with the assessor by 5 p.m. on February 15 of the calendar year in which the fiscal year begins, but files that affidavit on or before the following December 10, an exemption of the lesser of five thousand six hundred dollars ($5,600) or 80 percent of the full value of the dwelling shall be granted by the assessor.
(b) On claims filed pursuant to subdivision (a) after November 15, this partial homeowners’ exemption may be applied to the second installment, and if applied to the second installment, the first installment will still become delinquent on December 10 and the delinquent penalty provided for in this division will attach if the tax amount due is not paid.
If this partial homeowners’ exemption is applied to the second installment and if both installments are paid on or before December 10 or if the reduction in taxes from this partial exemption exceeds the amount of taxes due on the second installment, a refund shall be made to the taxpayer upon a claim submitted by the taxpayer to the auditor.