N.J. Stat. § 40A:11-19.1
A contracting unit, as defined in section 2 of P.L. 1971, c.198 (C.40A:11-2), shall pay interest on the amount due a business concern pursuant to a properly executed invoice, when required, if the required payment is not made on or before the required payment date.
Unless otherwise provided for in the contract, the required payment date shall be 60 calendar days from the date specified in the contract or if no required payment is specified in the contract, then the required payment date shall be 60 calendar days from the receipt of a properly executed invoice, or 60 calendar days from the receipt of goods or services, whichever is later. Interest shall not be paid unless goods and services are rendered.
Interest on amounts due shall be paid to the business concern for the period beginning on the day after the required payment date and ending on the date on which the check for payment is drawn.
Interest shall be paid at the rate specified by the State Treasurer for State late payments to business concerns pursuant to section 4 of P.L. 1987, c.184 (C.52:32-35).
Interest may be paid by separate payment to a business concern, but shall be paid within 30 days of the late payment.
A contracting unit may waive the interest payment for a delinquency due to circumstances beyond the control of the contracting unit, including but not limited to a strike or natural disaster.
As used in this section, "business concern" means any person engaged in a trade or business, including a private nonprofit entity operating as an independent contractor, providing goods or services directly to a contracting unit or to a designated third party and operating pursuant to a contract with a contracting unit which requires either a single payment or multiple payments, but shall not include a "public utility" as defined in R.S. 48:2-13.
N.J.S. § 40A:11-19.1