An accounting officer or a public officer authorized by him or her who signs or authorizes a payment instrument certifies the accuracy of every detail set out in the payment instrument and is responsible for ensuring—
(a) that the service specified in the payment instrument has been delivered;
(b) that the prices charged are according to the contract, approved scales or fair and reasonable according to current rates;
(c) that proper authority has been obtained for the expenditure in respect of which payment is made;
(d) that computation and costing have been verified and are arithmetically correct;
(e) that the person named in the payment instrument is entitled to receive payment; and
(f) that stores purchased have been correctly received and used or taken on charge.