The studied problem considers the inventory routing problem with time windows (IRPTW) in a supply chain that consists of a single warehouse and multiple retailers. The considered planning horizon is discrete and finite, and the decisions to optimize are: the quantities to supply to retailers, and simultaneously the sequence of retailers to visit in each time period. The system has a single vehicle with limited capacity, storage capacity constraints at retailers and a limited production rate at the depot is considered. It is required to meet the retailer´s demand. It is assumed that retailers have deterministic demand and not homogeneous. It is proposed a mathematical formulation based on mixed integer programming, and it is studied the impact of the time windows configuration on inventory routing decisions through two optimization methods. The first method optimizes decisions simultaneously, while the second proposed method considers sequential decisions, making it a heuristic method. A computational study with 80 instances adapted from the literature is presented. The results show that the method of simultaneous optimization has outperformed the heuristic optimization method generating potential savings in logistics costs of at least 6%.