In 2012, a committee of international experts from academia, business, and civil society published 'Toward Sustainability: The Roles and Limitations of Certification'. In addition to describing the history, key features and actors in voluntary standard systems (VSS), the report summarised the state of knowledge regarding VSS use and their potential to achieve conservation and other goals. It also enumerated existing evidence about VSS impacts, finding few studies and weak study designs. Since then, considerable effort has been made to fill research gaps. This report, funded by the Gordon and Betty Moore Foundation through the Meridian Institute, reflects on new VSS studies in the agricultural, forestry, marine fisheries and aquaculture sectors to revisit the issue of the state of knowledge about their conservation impacts and, going forward, consider how best to advance VSS impacts research.