(a) It is the policy of the State to make a payment under a procurement contract:
(1) within 30 days after the day on which the payment becomes due and the unit receives a proper invoice; or
(2) for a small business reserve contract, within 15 days after the day on which the payment becomes due and the unit receives a proper invoice.
(b) Interest shall accrue in accordance with § 15-104 of this subtitle.