The seminar provides current and practically relevant content in the field of cross-border employee assignments, including an update on the changed practice in the application of German social security agreements (DVKA circular of 22 April 2025), the consideration of third-country working days within the framework of the social security assessment of multi-country activities in the EU (ECJ ruling of 11 December 2025), as well as the new BMF letter of 19 December 2025 on the treatment of wages under double taxation agreements and the update of the OECD Model Tax Convention 2025 of 18 November 2025 on home office and permanent establishment.