Cal. Food & Agric. Code § 74659

Any vintner receiving an exemption or refund pursuant to Section 74658, shall, in addition to the requirements of Section 74654, maintain sales invoices and any other business documents specified by the commission as necessary to verify the claim. The records shall be preserved by the vintner for a period of two years and shall be offered and submitted for inspection at any reasonable time upon written demand of the commission or its duly authorized agent.