United Kingdom: Competition and Markets Authority amended merger guidance on jurisdiction and procedure entered into force

On 28 October 2025, the Competition and Markets Authority (CMA) adopted and implemented the amended merger guidance on jurisdiction and procedure. The amended guidance incorporates previously proposed changes to the CMA’s merger control procedures under a framework focused on pace, predictability, proportionality, and process. The amended guidance adjusts the 40-day phase 1 investigation process by promoting earlier identification of concerns through mandatory sessions with merging parties and earlier public notifications to allow third-party input during the pre-notification stage. It also introduces performance indicators aimed at accelerating straightforward decisions and shortening pre-notification periods. The guidance clarifies the CMA’s jurisdictional assessment, particularly the application of the “material influence” and “share of supply” tests. For material influence, shareholdings below 25% are generally not expected to meet the threshold unless additional factors are present, though even cases under 15% could require scrutiny if significant other factors indicate the ability to materially influence commercial policy. The revised guidance offers further detail on elements that may contribute to or fall short of establishing material influence, including board representation, commercial ties, and financial arrangements. For mergers with global or broader-than-national market relevance, the CMA may adopt a 'wait and see' approach if international remedies are likely to address competition concerns in the UK. The guidance continues previous adjustments to phase 2 procedures and includes measures to support transparency and more effective remedy assessment through increased engagement during investigations. The amended guidance applies mergers where formal phase 1 investigation commenced on or after 28 October 2025, as well as mergers referred to phase 2 on or after 28 October 2025.