In this paper, a mathematical model with flexible negotiation strategies for agent based negotiations is developed which can be applied suitably in bilateral/multilateral multi-issue negotiation environments. Unlike the existing approaches for offer value computation for the negotiation issues, this model considers not only the reservation values but also the offer values proposed in the preceding negotiation round. This approach for offer value computation enables the traders to reach consensus much quicker than the existing approaches. This model considers the compelling urge of the trader in buying/selling a product based on which the reservation values are adjusted automatically at the end of the negotiation process in order to reach consensus in a deal which is otherwise not possible. The formula devised in this model to determine the concession speed of each negotiation issue handles the dynamicity of the negotiation environment and reflects the importance of each negotiation issue from the traders’ perspective. The effectiveness of the proposed strategies is evaluated using various hypothetical cases representing the real-world negotiation scenarios in an e-commerce environment. The test results show that the proposed negotiation strategies are able to optimize the utility process and also improve the rate of reaching consensus in the negotiation process.