In this paper we consider the issue of formality in learning. Both formal and informal learning appear to be well-defined in educational discourse, in contrast with non-formal learning which is less clearly articulated. This lack of clarity around non-formal learning has consequences for its recognition by teachers and learners. To contribute to the conceptualisation of non-formal learning we carried out a literature review that helped us to identify dimensions of learning formality. This framework allowed us to discriminate the ways in which non-formal learning differed or matched with aspects of formal or informal learning. It also suggested to us that formality is fluid, and that learning with different formalities might co-exist in some learning environments. We then used our framework to develop tools for capturing evidence of non-formal learning. We describe these tools and how we used them in a pilot study to explore the features of non-formal learning in a formal, Year 12 classroom learning context in an English school. We use our pilot study outcomes to reflect on the utility of our data gathering methods. We also use the study outcomes to update our non-formal learning framework.