We consider an inventory routing problem in discrete time where a supplier has to serve a set of customers over a time horizon. A capacity constraint for the inventory is given for each customer and the service cannot cause any stock-out situation. Two different replenishment policies are considered, the order-up-to level and the maximum level policies. A single vehicle with a given capacity is available. The transportation cost is proportional to the distance traveled, whereas the inventory holding cost is proportional to the level of the inventory at the customers and at the supplier. The objective is the minimization of the sum of the inventory and transportation costs. We present a heuristic that combines a tabu search scheme with ad hoc designed mixed integer programming models. The effectiveness of the heuristic is proved over a set of benchmark instances for which the optimal solution is known.