California Code, Insurance Code - INS § 12995

(a) Notwithstanding any other provision of this code, all uncontested departmental billings for services or assessments authorized herein, which are not paid within 45 days of the invoice date, shall be subject to a late charge, unless waived or modified by the department. The late charge shall be 1 1/2 percent per month of the balance due. This late charge shall be compounded monthly.

(b) Billings from the department shall be postmarked within five working days of the invoice date. If the billing is postmarked more than five working days after the invoice date, the insurer shall be given 45 days from the date of the postmark to pay the amount due. In those instances where a billing is postmarked more than five working days after the invoice date, the insurer is required to submit the postmarked envelope with payment to avoid a late charge.

(c) Payments shall be postmarked by the due date to avoid a late charge. Except as provided in subdivision (d), contested billings for which the original amount is paid to the department after the 45 day period shall be subject to the late charge, unless waived or modified by the department. The insurer shall provide written notice of the contested billing and shall set forth the basis for the contestability in writing to the department prior to the due date.

(d) Late charges shall be tolled for the portion of the billing that is contested by an insurer. The commissioner shall consider the material submitted by the insurer and reach a decision on the contested billing within 30 days of receiving written notification that a billing is being contested. The commissioner's written decision on contested amounts shall be final and written notification, including a revised amount, if any, shall be provided indicating the basis for the decision. This written notification shall also include an invoice date from which an insurer shall be given 30 days to remit payment. This section shall not preclude an insurer from filing a petition for writ of mandate in accordance with the provisions of the Code of Civil Procedure.

(e) All late charges collected pursuant to this section shall be deposited into the General Fund.

(f) This section shall not apply to the Insurance Department Schedule of Fees and Charges pursuant to Section 12978.