This paper aim is to provide a decision support model to assist the invoice delivery for about 200 customers in a law firm in Bogotá, Colombia. Each customer has a service time and establishes the conditions for the delivery, i.e., day, place, and time window. Invoices are delivered by motorcycle. We collect and analyze real travel and service times for each day of the week. To determine an optimal plan for invoice delivery, a mathematical model was developed for dealing with customer requests. One week (5 days) was chosen as a planning period for invoice delivery. Comparing the current route planning approach against the proposed method, we obtain savings in the total operating time by 13.3 %. Results indicate that the implementation of the proposed optimization model in weekly planning decisions could decrease operating times and increase service quality significantly.