Cal. Rev. & Tax. Code § 2928

Any original unsecured roll containing the information set forth in the delinquent roll or in an abstract list may be destroyed by the county officer in possession of the rolls if (a) the destruction, in all cases, has first been approved by order of the board of supervisors, (b) the delinquent roll or abstract list has first been certified as correct and complete by the county auditor, and (c) a certified, permanent record on a substitute media has been prepared in accordance with Section 26205 of the Government Code and the substitute media will be retained for at least five years from the date of the creation of the original document. The substitute media may also be destroyed following the expiration of the five-year retention period.