Cal. Education Code § 45049

(a) When any school district employs a certificated employee to perform teaching or other services in addition to his or her regular teaching duties, or when a school district employs a certificated employee to perform teaching or other services at a summer school maintained by the district, the district shall pay the employee for the services either in one lump sum or at an hourly, daily, biweekly, quadriweekly, or monthly rate of pay. If the pay is in one lump sum, the district shall pay the employee within 10 days after the termination of the services. If the pay is at an hourly, daily, biweekly, quadriweekly or monthly rate, the district shall pay the employee within 10 days after the end of each calendar month or regular pay period during which the services are performed. (b) If a salary payment is not made timely as required by this section, the amount of the salary payment due shall be increased by an amount of interest on the unpaid amount for each day of delay. (c) A certificated employee of a school district who qualifies for a salary increase shall be paid the increased salary not later than three regular pay periods or three months, whichever is longer, after the employee files proper documentation where required for the salary increase. The district shall additionally pay the employee daily interest on the amount owed to the employee calculated from the date that the employee was entitled to the salary increase if the school district does not pay the employee his or her salary increase within three regular pay periods or three months, whichever is longer, after the employee files proper documentation where required for the salary increase. All amounts due the employee resulting from the salary increase and not paid to the employee at the time that the employee actually receives the salary increase shall be paid to the employee within 20 business days of the date that the employee actually received the salary increase. The district shall additionally pay the employee daily interest on the amount owed to the employee calculated from the date that the employee was entitled to the salary increase if the district does not pay the employee all amounts due the employee resulting from the salary increase within 20 business days following the date that the employee actually received the salary increase. (d) The amount of interest required by subdivisions (b) and (c) shall be determined by the method established in Section 19521 of the Revenue and Taxation Code.