El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In the current market, small- and medium-sized companies (SMEs) face losses due to poor process control. The core activities of information technology (IT) outsourcing service companies are to provide outsourcing services related to technology and information control, which is why it is crucial to work with standardized, efficient processes, to not affect the main process and resources involved. In this document, a case study of an SME is evaluated, related to a deficient billing process, which is not able to fulfill all of its orders. To solve the problem, we propose an IT outsourcing service model, based on the management of processes, knowledge, and change. After the model was validated, it was evidenced that it allowed the integration and finalization of the services provided by the company, increasing the monthly income by 80%.