California Code, Insurance Code - INS § 10235.9

(a) Every insurer shall report annually by June 30 the total number of claims denied by each class of business in the state and the number of these claims denied for failure to meet the waiting period or because of a preexisting condition as of the end of the preceding calendar year.

(b) The insurer shall provide every policyholder or certificate holder whose claim is denied a written notice within 40 days of the date of denial of the reasons for the denial and all information directly related to the denial.  Insurers shall annually report to the department the number of denied claims.

(c) The department shall make available to the public, upon request, the denial rate of claims by insurer.