Any amount due and payable pursuant to law and under an authorized, written procurement contract or a construction contract which remains unpaid for more than 45 calendar days after the receipt date shall accrue interest, at a rate specified by the Board of Estimates, for the period that begins 31 calendar days after the receipt date. If the written construction contract specifies a date before which payment must be made by the City, then the provisions of that contract shall apply to the payment of interest by the City. City Code, 1976/83, art. 1, §27A(c) Ord. 89-280