The Satellite Account on Nonprofit and Related institutions and Volunteer Work (NPI) brings various efforts together to offer comprehensive methodological guidance for creating a coherent satellite account on what we are calling the "third, or social economy, sector," the "TSE sector" for short, embracing three components: (a) NPIs that are not controlled by government; (b) certain related institutions that are not controlled by government, including in-scope cooperatives, mutual societies, and social enterprises; and (c) volunteer work. TSE institutions and volunteer work attract policy interest because of their growing economic presence, their extensive involvement in the solution of public problems, and the consequent contributions they are thought to make to the common good. Detailed instructions provided in this handbook will go a long way toward addressing important issues