The literature on the circular economy at the micro-level has mainly focused on the analysis of the circular business model and implementation of different circular-related practices, but the process of adoption by businesses of the circular economy is still under investigation. Therefore, through a study in the region of Aragón, Spain, the main circular economy-related activities implemented by a sample of 52 businesses are classified into four levels as an approach to the change process that firms can undergo to adopt the circular economy. In summary, it can be stated that circular economy-related activities are being introduced by businesses progressively, from a minor activity to a greater number of activities, but that these activities do not respond to the incremental closure of material loops within the circular economy framework. The applied indicators enhance the knowledge on the environmental management accounting applied to the CE for the reporting and the relations with stakeholders. In addition, the measurement of the introduction of the circular economy in different businesses is relevant for practitioners and for policy makers, in response to the institutional initiatives for the promotion of the circular economy at the territorial level.