UK Merger Control

Introduction

UK merger control is governed principally by the Enterprise Act 2002 (EA 2002), which replaced the public interest test under the Fair Trading Act 1973 with a competition-based assessment. The regime is administered by the Competition and Markets Authority (CMA), which has the power to review mergers to determine whether they may result in a substantial lessening of competition (SLC) within any market in the United Kingdom. Unlike the EU regime, UK merger control is voluntary in the sense that there is no mandatory notification requirement, but the CMA may investigate qualifying mergers on its own initiative.

Jurisdiction and Thresholds

The CMA has jurisdiction to review a merger where there is a relevant merger situation. Under section 23 of the EA 2002, this occurs where two or more enterprises cease to be distinct and either the turnover test or the share of supply test is met.

The turnover test is satisfied where the target enterprise has a UK turnover exceeding £70 million. The share of supply test is satisfied where the merger creates or enhances a share of supply of 25 per cent or more in the supply of goods or services of any description in the United Kingdom or a substantial part thereof. The share of supply test requires that there be an increment in the share of supply as a result of the merger, meaning that it applies not only to horizontal mergers but also to vertical and conglomerate mergers that strengthen an existing market position.

The CMA also has jurisdiction over completed mergers as well as anticipated mergers. Where a merger has been completed without prior CMA clearance, the CMA may investigate retrospectively and, if it finds an SLC, may impose remedies including the unwinding of the transaction through divestiture. This retrospective jurisdiction creates uncertainty for merging parties and provides a strong incentive to seek voluntary clearance through the CMA’s informal guidance or merger notice procedures.

The Merger Assessment Process

The CMA’s merger assessment proceeds through two phases. Phase 1 involves an initial investigation to determine whether the merger raises a realistic prospect of an SLC. The CMA has a statutory duty to refer mergers for a Phase 2 investigation where it believes there is a realistic prospect of an SLC, unless it accepts binding undertakings in lieu of reference. The Phase 1 investigation is conducted within a statutory timetable of 40 working days, extendable by 15 working days where the CMA considers that the case involves exceptional circumstances or where the merging parties offer undertakings in lieu.

If the CMA decides at Phase 1 that there is no realistic prospect of an SLC, it clears the merger unconditionally. If it identifies competition concerns, the merging parties may offer undertakings in lieu — binding commitments to divest assets or take other action to address the SLC — which the CMA may accept in appropriate cases. Undertakings in lieu must be clear-cut and capable of ready implementation, as the CMA will not accept complex or uncertain undertakings at Phase 1.

Phase 2 involves an in-depth investigation by an independent panel of CMA members, supported by CMA staff. The Phase 2 investigation considers whether the merger may be expected to result in an SLC and, if so, what remedies are appropriate. The statutory timetable for Phase 2 is 24 weeks, extendable by up to 8 weeks in exceptional circumstances. The Phase 2 inquiry group considers evidence from the merging parties, customers, competitors, and other stakeholders, and publishes a provisional findings report before reaching its final decision.

Substantive Assessment

The substantive test for UK merger control is whether the merger may be expected to result in an substantial lessening of competition (SLC) within any market or markets in the United Kingdom. The SLC test is applied by reference to the counterfactual — the competitive situation that would exist without the merger — and considers the competitive effects of the merger in the relevant markets.

The CMA assesses unilateral effects (whether the merged firm would have the ability and incentive to raise prices or reduce output unilaterally) and coordinated effects (whether the merger would increase the likelihood of coordination between remaining competitors). The CMA also considers vertical effects (whether the merger could result in input foreclosure or customer foreclosure) and conglomerate effects (whether the merger could enable the use of market power in one market to leverage a position in another).

Remedies

Where the CMA finds an SLC, it may impose remedies to address the competition concerns. The preferred remedy is typically the divestiture of a business or assets to create a new competitive entity or strengthen an existing competitor. The CMA expects divestiture remedies to be comprehensive and effective, and it requires the divested business to be viable and capable of competing effectively in the market.

Where divestiture is not feasible or proportionate, the CMA may accept behavioural remedies, such as commitments to supply competitors, to maintain separate operations, or to refrain from certain conduct. Behavioural remedies require ongoing monitoring and are generally considered less effective than structural remedies. The CMA may also require access remedies, granting competitors access to essential infrastructure or intellectual property.

Public Interest and Special Cases

Certain mergers may be subject to public interest considerations under sections 58 and 59 of the EA 2002. Public interest considerations include national security, media plurality, financial stability, and public health. Where a merger raises public interest concerns, the Secretary of State may intervene and make the final decision, displacing the CMA’s competition-based assessment. The public interest regime has been used in mergers involving defence, newspapers, and broadcasting.

Conclusion

UK merger control under the Enterprise Act 2002 provides a flexible and effective regime for assessing the competitive effects of mergers and acquisitions. The voluntary notification system, the two-phase investigation process, and the CMA’s broad remedial powers enable proportionate and evidence-based decision-making, balancing the benefits of market consolidation against the need to protect competition and consumers.