Cal. Gov. Code § 20772
When a member employed by the state is assigned to service for which he or she is compensated from funds not directly controlled by the state, he or she shall contribute to the retirement fund at the rate certified by the board, applied to the compensation earnable by him or her immediately preceding that assignment. The head of each state agency in which a member assigned to that service is employed shall notify the member of his or her individual rate of contribution and the amount of the monthly contribution payable by him or her to the retirement fund, and shall furnish monthly to the board a list of the employees so assigned during the preceding month, together with the rate of compensation earnable by each. Within 15 days of the receipt of compensation for that service in any month, the member rendering that service shall transmit his or her contribution in respect to that service to the office of this system in Sacramento. Any contribution remaining unpaid for 30 days after the completion of the assignment of the member and his or her return to the state payroll shall be deducted from his or her compensation for the next succeeding month or months as the board may provide by rule.
Ca. Gov. Code § 20772