Cal. PCC § 10261.5

(a) Any state agency which fails to make any progress payment within 30 days after receipt of the payment request from a contractor on a construction contract for an undisputed payment request, which was properly submitted by the contractor to the agency, shall pay interest to the contractor equivalent to the legal rate set forth in subdivision (a) of Section 685.010 of the Code of Civil Procedure. Any state agency which independently calculates the amount due on a progress payment and which fails to make a progress payment within 30 days of the first submittal of the estimate for each contract by the engineer, shall pay interest to the contractor equivalent to the legal rate set forth in subdivision (a) of Section 685.010 of the Code of Civil Procedure. In the event that the payment is not made within 30 days of receipt of the contractor’s request or the first submittal by the engineer, and the Controller has processed the payment within 14 days of receipt of the request or submittal, the contracting state agency shall pay interest to the contractor equivalent to the legal rate set forth in subdivision (a) of Section 685.010 of the Code of Civil Procedure. In the event that the payment is not made within 30 days of receipt of the contractor’s request or the first submittal by the engineer, and the contracting state agency has processed the payment within 16 days after receipt of the request or submittal, the Controller shall pay interest as provided in Section 685.010 of the Code of Civil Procedure.

For purposes of this section, a payment request shall be considered properly executed if funds are available for payment of the payment request, and payment is not delayed due to an audit inquiry by the Controller.

(b) Upon receipt of a payment request, each agency shall require:

(1) That each payment request be reviewed as soon as practicable after receipt for the purpose of determining that a payment request is a proper payment request.

(2) Any payment request determined not to be a proper payment request suitable for payment shall be returned as soon as practicable, but not later than seven days, after receipt, specifying the reasons that the payment request is not a proper payment request.

(3) The number of days available to a state agency to make a timely payment of payment request without incurring interest shall be reduced by the number of days by which an agency exceeds the requirements of paragraph (2).