EIOPA adopted XBRL for Solvency II supervisory reporting in 2011. XBRL is a reporting format that classifies balance sheet and business information and is particularly suited for aggregating and comparing data. The Solvency II Directive only requires National Competent Authorities (NCAs) to report to EIOPA using XBRL – it is up to the NCAs to decide whether to use XBRL to collect data from undertakings. XBRL has been successfully used by the FDIC in the USA for bank regulatory reporting since 2005. The technology is relatively new in Europe and to ease its take-up, EIOPA is designing a software tool aimed at NCAs and smaller undertakings. The EIOPA XBRL Tool for Undertakings, or T4U, has been in development for some years. According to EIOPA’s working plans it is expected to be released in the 4th quarter this year. Research conducted by Solvency II Wire revealed that many NCAs intend to rely on the EIOPA T4U both for their own use and as a solution for firms, but to date EIOPA has only published technical information about its XBRL work and little is known about how the T4U will be used in practice by filers (i.e. reporting entities). Firms are currently evaluating Pillar III solutions and many plan to rely on the tool. Therefore, understanding the capabilities of the T4U is important for Solvency II planning.