Electoral registration in the UK is often critiqued for making it hard for voters to participate in elections. However, without a tool for a systematic, international comparison, we cannot know if the UK’s system is unusually difficult. To tackle this issue, we make a methodological contribution to the comparative international study of electoral registration. Using four criteria of difficulty, we create an index of difficulty of registration by adapting an American scheme [Jansa, J. M., Motta, M.