There is a widespread dissatisfaction among nonprofit leaders and managers, private funders and public decision-makers concerning the current systems of social impact assessment of nonprofit organizations/social enterprises (NPO/SE). The systems of performance measurement of NPO/SE vary greatly in relationship to a series of endogenous and exogenous variables related to different organizational environments: economic, political, social and cultural. The aim of this article is to present an innovative theoretical framework on the basis of which it is possible to define a set of indicators for the evaluation of the social added value produced by NPO/SE. Our hypothesis is that NPO/SE are characterized by their ability to generate different outcome at each of the dimensions of social life: micro, meso and macro. Meaning, a sense of responsibility at the micro level; relational goods at the meso level; and social capital at the macro level. The article illustrates the assessment tool called S.A.V.E. applied, as empirical reference, to three Italian social enterprises operating in the field of health and social services (local welfare systems).