Cal. Rev. & Tax. Code § 5097
(a) An order for a refund under this article shall not be made, except on a claim:
(3)
(A) Filed within one year, if an application for a reduction in an assessment or an application for equalization of an assessment has been filed pursuant to Section 1603 and the applicant does not state in the application that the application is intended to constitute a claim for a refund, of either of the following events, whichever occurs first: