The paper highlights the problem of modelling the decision making process in the logistics system consisting of parallel chains of supplies. The structure of the system is introduced and the change of the state of the order matrix as well as the change of the state of decisions is emphasized. The way how to calculate either real costs or costs of delays is shown. The method of evaluating the state of the decision making process is proposed and sample guidelines for the possible combination of decisions followed by the possible logistics routes are given. Finally, the method of making the final decision about initiating the manufacturing process is introduced. Additionally, recommendations for the development of the system for calculating costs of the reverse flow of the decision-making process are proposed.