ERP systems have been studied in various situations and contexts, both geographical and social and economic. By its turn, institutionalization of Management Accounting practices has also received attention. Wether it's in the context of business process reengineering, large companies against small companies, developed countries or not, in family businesses or even under regulatory pressures, several research methods have investigated how the practice of Management Accounting in the institutional environment develops and evolves, aiming to shed light on the processes of change and make them less expensive and more successful. This paper, through a case study, analyzed the process of institutionalization of the Management Accounting practices as a result of the implementation and usage of an ERP system in a small business retailer. The results obtained through interviews point to the fact that using a new system, even years after implementation, did not contribute to the change in management practices of the company analyzed, keeping the previous practices, although operational processes have evolved as a result of the system's implementation. Thus, it is possible to conclude that, if one disregards pre-existing institutions in the change process, implementing new ERP systems is not enough to cause disruptions to institutionalize new management accounting practices. It is recommended that this research be replicated in small businesses in similar situations in order to understand why ERP systems may not be useful for institutionalizing Management Accounting practices.