Covid-19 has highlighted the inadequacy of UK social security but also the lack of consensus among progressive actors about what would be a better system. One way forward is to focus on the principles that should underpin social security. We present outcomes from a project in which principles were considered by a panel of Expert by Experience benefit claimants. We argue that while scholars often engage in descriptively identifying social security principles in existing policy, the bottom-up approach presented here offers a way of generating normative principles to guide an improved future system. We identify key contributions of this bottom-up approach relating to: the critical importance of principles as a guide to the fundamental purpose of social security, and policy making; the relationship between the treatment of claimants and benefit levels as co-dependent; and how a bottom-up process can produce results that engage with and contribute holistically to the debate.