Abstract: In manufacturing enterprise, if product delivery date is set to be too late, an enterprise would lose its costumer order because of the lack of deliver time advantage. However, if the delivery date is set to be too early, enterprises would have deficit because of overload and increased cost. To predict order delivery date for small and mediumsized manufacturing enterprises operating in a maketoorder mode, price, demands, earlier completion, later delivery, overtime work, association, loss rate, and so on are analyzed. Then, with income maximization as objective, a deliveryincome model is presented. By using Matlab, a reallife case problem is given to verify the usefulness of the model. Results show that extending the due date by effective strategies, such as pricing strategies, all orders can be done by regular and overtime production. The due date that corresponds to full capacity is the optimal promised delivery time in the sense of gain maximization.