The European Single Digital Gateway Regulation (SDGR) mandates the development of a technical system for the cross-border exchange of evidences between European member states to be used in a number of administrative procedures. The system was due to be operational in December 2023. In this article we focus on specific developments and relevant new aspects for the European eGovernment, derived from the Austrian implementation of the SDG Once Only Technical System (OOTS). The article describes mainly technical approaches, which are either new in the internal technical system or in the user experience, including a pan-European method for finding equivalent evidences in other member states, novel aspects of the implemented IT-systems, methods of handling a potentially complex user experience with a significant number of handovers (also cross border), and considerations regarding data management, the use of artificial intelligence and data protection. The article also exhibits an overview over related topics and projects.