N.D. Cent. Code § 48-01.2-14
If a governing body fails or neglects to consider any estimate properly submitted, pay any estimate approved, or make final payment upon completion and acceptance of a public improvement, for a period of more than thirty days from the date of approval of the estimate or the completion and acceptance date, the governing body shall pay interest on the estimate or final payment from the date of approval. The interest rate must be the rate per annum of two percentage points below the Bank of North Dakota prime interest rate as set thirty days from the date of the estimate or completion date until the issuance of a proper warrant for the payment. The governing body shall compute and add the interest to the face of the estimate or final payment and the interest must be charged to the fund upon which payment for the contract is to be made. No payment for, or on account of, any contract made under this chapter may be made except upon estimate of the architect, engineer, or contractor as provided in section 48-01.2-13.
N.D.C.C. § 48-01.2-14