PurposeFor clients to understand social insurance decisions and processes, information from authorities needs to be comprehensible, and clients need sufficient individual abilities. These dimensions are captured by the concept social insurance literacy, which has been operationalized into a measure, the Social Insurance Literacy Questionnaire (SILQ). The aim of this study was to describe the development of the SILQ and evaluate its psychometric properties using Rasch measurement theory.MethodsThe development of the SILQ included a Delphi study and cognitive interviews. A preliminary version, divided on four scales corresponding to the domains of the concept (obtaining information, understanding information, acting on information, and system comprehensibility) was psychometrically evaluated according to Rasch measurement theory, in a survey to a stratified random sample of people on sick leave (n = 1151) sent out in the fall of 2020.ResultsOverall, the items in the final version of the SILQ demonstrated good fit to the Rasch model, and the response scale worked as intended. Unidimensionality was supported for all scales, but minor problems with local dependency was detected for three items. The person separation was 0.80 for the Obtain scale, 0.82 for the Understand scale, 0.68 for the Act scale, and 0.81 for the System scale. Corresponding ordinal alpha values were 0.91, 0.91, 0.86, and 0.91, respectively.ConclusionThis study is a first step toward exploring literacy in the social insurance field. The SILQ covers individual abilities and systems' comprehensibility, and the results show that it has acceptable psychometric properties.