UK Competition And Markets Authority Publishes Final Revised Merger Efficiencies Guidance

1. Summary

On 3 September 2026, the UK’s Competition and Markets Authority (“CMA”) published revised guidance on its approach to assessing merger efficiencies. The new guidance replaces paragraphs 8.2 to 8.27 of the CMA’s Merger Assessment Guidelines, which explain the substantive approach of the CMA to its analysis when investigating mergers.

Whilst the underlying framework for assessment of efficiencies claims remains unchanged, the changes to the guidance mark a shift toward greater openness to merger parties’ efficiencies arguments on the part of the CMA. Notably, the new provisions include more detailed guidance regarding sources of evidence and evidentiary standards—for example, a greater openness to evidence generated after the transaction was already in contemplation—, the recognition that remedies to secure efficiencies may be capable of resolving the CMA’s concerns (particularly in the case of time-limited anticompetitive effects), and reassurance that the submission of