Cal. Rev. & Tax. Code § 828

Any person with knowledge or records pertinent to the appraisal of state-assessed property shall make them available to the board on request. The person shall make available at his principal place of business, principal location, or principal address in California, or at a place mutually agreeable to the board and the person, a true copy of business records relevant to the amount, cost, and value of all property that he owns, claims, possesses, or controls within the state.