Cal. Ed. Code § 23002
Member and employer contributions required by this part and Section 44987 are due in the office of the system five working days immediately following the period covered by the monthly report upon which the compensation earned during the period is being reported and from and upon which the contributions are due. Payments shall be delinquent on the sixth working day thereafter and regular interest on delinquent payments shall begin to accrue as of that day. The board shall authorize estimated payments of not less than 95 percent of the contributions due, and, in that case, the balance of contributions payable shall be due in the office of the system no more than 15 working days following the period covered by the monthly report upon which the contributions are based. This additional payment shall be delinquent on the 16th working day thereafter, and regular interest shall begin to accrue as of that day.
Ca. Educ. Code § 23002