A proper invoice submitted by the contractor shall be required to initiate any payment, except where the contract provides that the contractor will be paid at predetermined intervals without having to submit an invoice for each such scheduled payment and, for the purposes of determining eligibility for payment of interest and subject to the exception and time-to-rectify provisions of sections 4701.7 and 4701.8 of this Part, the date by which contract payment must be made in order for the authority not to become liable for interest payments shall be the payment due date specified in accordance with the contract.