Purpose: Sickness insurance and workers' compensation systems decide on peoples' eligibility for benefits, and are commonly based on medical certificates and assessments of work ability. Systems differ in the extent to which they preserve clients' dignity and right to fair assessments. In this article, we define a new concept for studying interactions between individuals and systems: social insurance literacy, which concerns how well people understand the different procedures and regulations in social insurance systems, and how well systems communicate with clients in order to help them understand the system. Methods: The concept was defined through a scoping literature review of related concepts, a conceptual re-analysis in relation to the social insurance field, and a following workshop. Results: Five related concepts were reviewed for definitions and operationalizations: health literacy, financial/economic literacy, legal capability/ability, social security literacy, and insurance literacy. Conclusions: Social insurance literacy is defined as the extent to which individuals can obtain, understand and act on information in a social insurance system, related to the comprehensibility of the information provided by the system. This definition is rooted in theories from sociology, social medicine and public health. In the next step, a measure for the concept will be developed based on this review. À IMPLICATIONS FOR REHABILITATION Social insurance literacy is a new concept that is based on theories in sociology, social medicine and public health. It provides conceptual orientation for analyzing factors that may influence different outcomes of peoples' contacts with social insurance systems. The concept is of relevance for rehabilitation professionals since it focuses on how interactions between individuals and systems can influence the rehabilitation process. The study will in the next step develop a measure of social insurance literacy which will have practical applications for rehabilitation professionals.