Cal. RTC § 470

(a) Upon request of an assessor, a person owning, claiming, possessing, or controlling property subject to local assessment shall make available at his or her principal place of business, principal location, or principal address in California, a true copy of business records relevant to the amount, cost, and value of all property that he or she owns, claims, possesses, or controls within the county.

(b) (1) Upon written request of an assessor, the assessee or the assessee’s designated representative shall transmit the business records described in subdivision (a) by mail, or in electronic format if the business records are available in electronic format or have been previously digitized. This paragraph shall not be construed or interpreted to limit the assessor’s authority to also examine information or records described in subdivision (a).

(2) Information or records requested by the assessor under this subdivision shall be transmitted within a reasonable time period.

(c) In the case of a taxpayer that has its principal place of business outside of California and has been requested to make business records available pursuant to subdivision (a), that taxpayer may, as an alternative to making the requested business records available pursuant to the terms of that subdivision, pay the county the amount of reasonable and ordinary expenses for food, lodging, transportation, and other related items incurred by the assessor’s representative, in traveling to the place outside California where the requested business records are available for examination and performing his or her official duties with respect to the examination of those records.