In a supply chain environment, supply chain entities need to make joint decisions on the transaction of goods under the issues quantity, delivery time and unit price in order to procure/sell goods at right quantities and time while minimizing the transaction costs. This paper presents our negotiating agent designed for Supply Chain Management League (SCML) in the International Automated Negotiation Agents Competition (ANAC). Basically, the proposed approach relies on determining reservation value by taking the changes in the inventory stock into account. We have tested the performance of our bidding strategy in the competition simulation environment and compared it with the performance of the winner strategies in ANAC SCML 2019. Our experimental results showed that the proposed strategy outperformed the winner strategies in overall.