E-procurement systems allow governments to efficiently management their contracts by improving interactions with suppliers, and by increasing transparency. Governments generally choose their suppliers based on the minimum price. However, other criteria than price may be considered to help governments choose the best suppliers. This paper proposes a formal reputation model that is intended to determine the winners of an eprocurement process. The proposed model combines three elements: (1) the direct reputation of the supplier, (2) the indirect reputation of the supplier, and (3) the difference in beliefs between the government and the supplier. Using a multi-agent approach, the proposed model compares between situations where reputation is integrated along price for selecting suppliers and when it is not. Results show that the proposed reputation model may lead to lower costs.