As social and solidarity economy (SSE) entities are increasingly requested to demonstrate their positive contribution to society, social impact measurement can help them understand the additional, net value generated by their activities, in the pursuit of their mission and beyond. Policy plays an important role to facilitate a conducive environment to unlock the uptake of social impact measurement among SSE actors. Drawing on a mapping exercise and good practice examples from over 33 countries, this international policy guide navigates how policy makers can support social impact measurement for the social and solidarity economy by: (i) improving the policy framework, (ii) delivering guidance, (iii) building evidence and (iv) supporting capacity. Building on the earlier publication Social Impact Measurement for the Social and Solidarity Economy released in 2021 the guide is published under the framework of the OECD Global Action “Promoting Social and Solidarity Economy Ecosystems”, funded by the European Union’s Foreign Partnership Instrument.