This article discusses the fast-approaching deadline for sponsors to transition ongoing clinical trials in the EU/European Economic Area from the Clinical Trials Directive 2001/20/EC to the Clinical Trials Regulation 536/2014. In particular, the authors discuss the medical writer’s crucial role in ensuring that documentation meets the regulation harmonisation and transparency requirements; they also highlight challenges seen when redacting commercially confidential information in the preparation of transition applications.   Medical Writing. 2024;33(3):22–25. https://doi.org/10.56012/ghkj9468