Cal. Health and Safety Code § 1374.255

(a) This section shall apply to grandfathered health care service plan contracts and nongrandfathered health care service plan contracts in the individual or small group markets that are issued, amended, or renewed on or after January 1, 2017. (b) Notwithstanding paragraph (1) of subdivision (b) of Section 1374.20, a health care service plan contract shall not change the cost-sharing design during the plan year, except when required by state or federal law. (c) For purposes of this section, the following definitions shall apply: (1) “Cost sharing” includes any copayment, coinsurance, deductible, or any other form of cost sharing by the enrollee other than the premium or share of premium. (2) “Plan year” has the meaning set forth in Section 144.103 of Title 45 of the Code of Federal Regulations. For nongrandfathered health care service plan contracts in the individual market, “plan year” means the calendar year. (3) “Cost-sharing design” means the amount or proportion of cost sharing applied to a covered benefit.