A number of established data-collection initiatives and organisations provide helpful insights on the social impact investment market. However, data efforts are still highly fragmented and not comparable across studies. This chapter presents data and transparency efforts undertaken alongside the OECD Social Impact Investment Initiative’s data work stream. The chapter outlines initial steps towards a global data framework on social impact investing. It starts by presenting transparency principles. It then discusses data on transactions and performance, also looking at data available beyond social impact investment that could inform help inform the SII market. The chapter also presents social impact investment platform efforts and approaches for measuring impact. It concludes by calling for greater coordination and Social Impact Investment laying out recommended steps to move forward from the initial data standards to internationally adapted and globally used data standards.