This article aims to deal with the problem of reallocating supply, in both its real and planned contexts, to orders that result from the order promising process under shortage. To this end, we propose a system dynamics-based simulation model to facilitate modelling for order managers, and to provide a graphic support tool to understand the process and to make decisions. The basis of the simulation model's structure is a mixed integer linear programming approach which intends to maximise profits by considering the possibility of making partial and delayed deliveries. To illustrate, we consider a real world problem from the ceramic sector that contemplates 35 orders. We obtained a solution by a mathematical programming model and a simulation model. The results show the simulation model's capacity to obtain nearoptimum results, and to provide a simulated history of the system.