This policy perspective was developed at the request of the Directorate for Education Reform, Scotland (United Kingdom) to provide an overview of how countries across the OECD assess social and emotional skills in upper secondary education. It is accompanied by, and draws on material from, a Peer Learning Discussion on the same topic in March 2023 in Scotland. It aims to provide an overview of literature and country approaches in an area where there is presently limited comparative information on national and system-wide approaches. The policy perspective addresses two key questions about country practices in assessing social and emotional skills (variously known among OECD countries as social and emotional skills, non-cognitive capacities, 21st-century skills, transversal competencies, and complex competencies): a) how do countries collect information on social and emotional on a systemic level; i.e. outside formal upper secondary certification, and b) how do countries assess social and emotional skills for the purposes of upper secondary certification? To answer these questions, the policy perspective provides an inventory and synthesis from 12 countries of approaches, models, and strategies used at the national level to document, assess, and recognise similarly challenging skills, and detailed cases of the model and strategy for assessment of social and emotional skills in Canada (British Columbia), Finland, and New Zealand.