Cal. HSC § 1366.26

A qualified beneficiary electing continuation coverage shall pay to the health care service plan, on or before the due date of each payment but not more frequently than on a monthly basis, not more than 110 percent of the applicable rate charged for a covered employee or, in the case of dependent coverage, not more than 110 percent of the applicable rate charged to a similarly situated individual under the group benefit plan being continued under the group contract. In the case of a qualified beneficiary who is determined to be disabled pursuant to Title II or Title XVI of the United States Social Security Act, the qualified beneficiary shall be required to pay to the health care service plan an amount no greater than 150 percent of the group rate after the first 18 months of continuation coverage provided pursuant to this section. In no case shall a health care service plan charge an employer an additional fee for administering Cal-COBRA other than those incorporated in the risk adjusted employee risk rate as provided for in subdivision (i) of Section 1357.