California Code, Government Code - GOV § 13995.108

(a) The county may require assessed businesses to maintain books and records that reflect their income or sales as reflected in the assessment, and to furnish the county treasurer/tax collector with any information that may, from time to time, be requested by the treasurer/tax collector, and to permit the inspection by the treasurer/tax collector of portions of books and records that relate to the amount of assessment.

(b) Information pertaining to assessed businesses obtained by the county treasurer/tax collector pursuant to this chapter shall be confidential and shall not be disclosed except to a person with authority to obtain the information, any attorney hired by the county treasurer/tax collector who is employed to give legal advice upon that information, or by court order.

(c) Information obtained by the county treasurer/tax collector in order to determine the assessment level for an assessed business shall be exempt from the California Public Records Act (Chapter 3.5 (commencing with Section 6250) of Division 7 of Title 1).