‘Why write a clinical study report (CSR)? What are the guidance documents? Can I interpret them? Can I deliver my CSR on time?’ This article addresses these questions – and others, provides a companion guide to CSR authoring for preregistration drug trials intended for regulatory submission in the EU, provides links to applicable regulatory guidance documents, and offers experience-based insights. Between 2008 and 2013, the authoring timeline for a medium complexity first draft (mean [SD]: 16.9 [8.2]; range: 5–45 working days) and final CSR from the first draft (mean [SD]: 25.7 [21.1]; range: 3–120 working days) varied widely across the industry. Understanding regulatory requirements and utilising project intelligence leads to informed CSR authoring and scheduling, thereby assuring a high-quality, on-time, final CSR.