(1) Subject to the specific terms of a public procurement contract, the accounting officer shall ensure that a contractor is paid on the basis of the submission of an invoice in accordance with the closing date and time set out in the public procurement contract.
(2) In the case of the public procurement of works, a contractor is not entitled to any payment in respect of work performed in the execution of the public procurement contract unless he or she has, together with his or her claim for payment, filed a certificate —
(a) stating rates of remuneration and hours of work of the various categories of workers employed in the execution of the public procurement contract;
(b) stating whether any remuneration payable in respect of work done is due;
(c) containing such other information as the procuring entity requires to satisfy itself that the provisions of this Act have been complied with.