The interest in evaluation and impact assessment of the social and solidarity economy (SSE) is reaffirmed year upon year. In the recent decades however, demands have grown and changed the way SSE organizations report on their activity. We are moving from a culture of evaluation of processes and results to the development of an expertise in measuring economic, social and environmental impacts. This represents an Opportunity of the SSE, but it also poses challenges. This special issue aims to contribute to understand the approaches being developed for the SSE and examine the incidences they have on organizational practices and overall representation of the sector. In this editorial introduction we introduce the research topic, describe the content of the current special issue, and conclude with possible directions for future research.