With the Act on the Modernization of Partnership Law (Gesetz zur Modernisierung des Personengesellschaftsrechts – MoPeG), a comprehensive reform of German partnership law will come into force on 1 January 2024. This also entails a large number of legal changes for the basic form of partnerships (Personengesellschaften), the partnership under civil law (Gesellschaft bürgerlichen Rechts – GbR). This article is intended to summarize the main changes of the MoPeG for the GbR. In particular, it will be shown which changes of the MoPeG (i) merely codify – already applicable – established case law and which, on the other hand, (ii) actually constitute material changes to the previous legal situation. In particular, so-called external GbRs (Außen-GbR), which participate in legal transactions themselves, will have to take a number of changes into account in future. For example, there is the possibility of voluntary registration of the GbR in a company register (Gesellschaftsregister), whereby this can also become a “registration obligation through the back door” in practice due to legally standardized pre-registration requirements.