CMA publishes updated guidance on UK merger procedure 

On 28 October 2025, the Competition and Markets Authority (CMA) published its updated merger guidance on jurisdiction and procedure (the Guidance), which implements the CMA's '4Ps' strategic framework (of Pace, Predictability, Proportionality and Process) and seek to ensure that merger control supports the UK Government's economic growth objective. The Guidance has been published together with the new Merger Notice template and updated guidance on the CMA's mergers intelligence function (MIC Guidance), which were both updated to reflect the changes made to the Guidance. The updated Guidance follows the CMA's new Mergers Charter in March 2025 (see our March 2025 update) and a public consultation on the draft guidance between 20 June and 1 August 2025 (see our July 2025 update).

What you need to know

• The guidance on the material influence and share of supply jurisdictional statutory tests, which the CMA frequently applies in merger control investigations, has been updated to clarify the CMA's approach. The UK Government separately confirmed in October 2025 that it plans to launch a consultation "in the coming weeks" proposing legislative changes to these tests.
• The CMA will consider adopting a "wait and see" approach to global transactions, noting it is less likely to open investigations where markets are global and the transaction is subject to review by other regulators, or where remedies agreed in other jurisdictions would be likely to address any competition concerns in the UK.

So why now?

The Government published its updated strategic steer to the CMA on 15 May 2025, which sets out the Government's overarching aim for economic growth and the role of the CMA in delivering that aim. Among other changes, the steer requires the CMA to review its procedural guidance to increase accessibility, transparency and provide "proactive, transparent, timely, predictable and responsive engagement with businesses".

The CMA is increasingly focusing on its '4Ps' framework, which was first announced by the CMA's Chief Executive Officer in November 2024 and formally adopted into the CMA's new Mergers Charter in March 2025, to ensure that all areas of its work adhere to the principles of 'Pace', 'Predictability', 'Proportionality' and 'Process' (see our March 2025 update).

The Guidance seeks to incorporate the UK Government's overarching economic objective and the '4Ps' into the CMA's merger control review process. The CMA published revised draft guidelines for consultation in June 2025 (see our July 2025 update) and following stakeholder feedback, has now published final revised Guidance.

Updates to the CMA's pre-notification procedure and phase 1 merger review process

The Guidance has been updated to set out a commitment by the CMA to ensure that the 'pre-notification stage' of merger investigations (i.e. the period between the CMA issuing a process letter and the commencement of the statutory phase 1 review) will "typically" be limited to 40 working days (from the current average of 65 working days). This commitment is intended to support the delivery of the first of the '4Ps'; pace.

In order to ensure that the 40 working day commitment is achieved, the CMA has set out new requirements for merging parties to adhere to before it will commence the formal pre-notification stage. The CMA must now be satisfied that the merging parties' draft Merger Notice template, or response to an enquiry letter, "provides the necessary information for the CMA to carry out the initial stages of pre-notification, such as prioritising the most relevant theories of harm and engaging with relevant third-parties". In practical terms, this includes identifying in the draft Merger Notice template all horizontal overlaps and vertical links between the merging parties' businesses, and providing all supporting documentation requested in the Merger Notice template (including, for example, internal documents), relevant third-party contact details and consent for the CMA to announce the commencement of the pre-notification stage on its website. Only once the CMA is satisfied that it has received all of this requested information will it trigger the formal pre-notification stage.

Another target to improve upon pace is the CMA's intention, as set out in the Guidance, to clear "straightforward" phase 1 cases within 25 working days of the 40 working day statutory deadline. Of the 11 Phase 1 decisions announced by the CMA since 1 September 2025, six have been cleared within 25 working days. This change represents a significant improvement on the current average of 35 working days for Phase 1 cases and brings the CMA's Phase 1 review timeframe for simple cases in line with that of the European Commission. The shorter clearance decisions that are typically seen in relation to European Commission Phase 1 clearances under the simplified procedure are also likely to become a familiar sight in the UK, as the CMA has confirmed that, to meet this new deadline, its decisions will be in a more summarised form. In recent months, the CMA has published multiple Phase 1 clearance decisions that are shorter than ten pages (see, for example the recently published decisions in Global Payments / WorldPay (nine pages) or Norcos / Fibo (five pages)).

Earlier engagement with the merging parties

The Guidance has been updated to state that the CMA will invite the merging parties to hold a teach-in session during the pre-notification stage so that the case team can better understand the industry and the merging parties' businesses. The CMA anticipates that this teach-in will be led by the "key commercial and operational staff" from the merging parties' businesses (as opposed to their external advisors) and will streamline the early stages of the merger review process by giving the case team an opportunity to ask pertinent questions and focus on key issues. A senior member of the CMA's case team will also attend these teach-ins and offer the merging parties a brief outline of the envisaged process.

In addition to early engagement with the merging parties at a teach-in session, the CMA states that it will hold two informal update calls (at "approximately 20 working day intervals after the commencement of pre-notification"). The Guidance acknowledges that the second call may fall before or after the CMA formally commences its phase 1 investigation. The CMA anticipated in its consultation that early engagement will have a positive impact on its overall process.

The CMA's jurisdictional tests

The CMA has updated its Guidance on the application of both the "material influence" and "share of supply" tests for establishing jurisdiction over transactions. The jurisdictional tests are set out in legislation and the Government announced in October 2025 that it will consult in the coming months on legislative changes to provide greater certainty on the application of these tests.

Amendments to clarify the scope of the material influence test

Under the UK merger control regime, the CMA has jurisdiction to investigate mergers that constitute a "relevant merger situation", which arises when two or more enterprises cease to be distinct. Enterprises cease to be distinct where they are "brought under common control or ownership" in at least one of following circumstances: (i) legal (de jure) control, (ii) de facto control or (iii) material influence.

Building upon its recent decisional practice, the CMA has clarified its approach to identifying material influence in the updated Guidance. When undertaking this assessment, the CMA will consider the extent to which the acquirer is able to influence the commercial strategy of the target based on:

• the acquirer's ability to block or approve commercial decisions by way of special resolutions;
• the acquirer's ability to appoint members to the target's board; and
• other agreements between the merging parties that puts the target in a position of dependency when making commercial decisions.

It is important to note that a finding of material influence does not necessarily require that the acquirer is able to influence the day-to-day operation of the target, nor is there a requirement that the acquirer has ever actually exercised material influence over the target. The potential to exercise material influence in relation to the target, and in particular its commercial strategy, is sufficient.

The Guidance confirms that an acquirer's shareholding will typically have a direct bearing on its ability to influence the target entity, and that a shareholding exceeding 25% will generally confer material influence as it enables an acquirer to block special resolutions. In contrast, minority shareholdings below 25% are unlikely to result in the acquisition of material influence "in the absence of other factors", such as the right to appoint board members, or the presence of financial agreements, commercial agreements, or agreements to provide consultancy services to the target entity that enable the acquirer to materially influence the target's commercial policy. The Guidance further states that it is only in exceptional circumstances and in the presence of "significant other factors" that the acquisition of a minority shareholding of less than 15% will confer material influence on the acquirer (in contrast to the previous guidelines, which referred only to "other factors"). This change reflects the very small number of previous cases where the CMA (or its predecessors) have found minority shareholdings of less than 15% to confer material influence.

The CMA's earlier consultation document stated that the amendments it has made in relation to the material influence test ensures a greater level of predictability.

Amendments to reflect recent developments in relation to the share of supply test

The Guidance has also clarified the application of the share of supply test in an attempt to increase its predictability. The share of supply test is one of the thresholds (alongside the turnover test and hybrid test) that determines whether a relevant merger situation qualifies for investigation.

The share of supply test is met where, as a result of the merger, a share of 25% or more in the supply or purchase of goods or services of a particular description in the UK (or in a substantial part of the UK) is created or enhanced. As a result of amendments introduced by the Digital Markets, Competition and Consumers Act 2024, this test is subject to the requirement that at least one of the parties has a turnover in the UK that exceeds £10 million. The Guidance has been updated to include two important changes to the CMA's approach in relation to the share of supply test:

• The first change concerns the CMA's ability to apply the share of supply test in relation to multiple factors including value, cost, price, quantity, capacity and number of workers employed (these criteria are explicitly referred to in the Enterprise Act 2002). The Guidance confirms that the CMA will limit its consideration to these factors and will "typically" rely on the value and/or volume of goods sold when applying the share of supply test (although this continues (intentionally) to leave the CMA with significant flexibility to establish jurisdiction).
• The second amendment confirms that in determining the description of goods and services under the share of supply test, the CMA will consider those goods and services which "are relevant to any potential competition concerns arising from the merger". In this connection, the CMA refers to paragraph 144 of the Competition Appeal Tribunal's judgment in Sabre Corporation v Competition and Markets Authority [2021] CAT 11, which found that the purpose of the share of supply test is "to identify a merger which does not meet the turnover test, but in respect of which there is a sufficient prospect of a competition concern arising from an overlap in relevant commercial activity as to render it worthy of investigation". The Guidance further states that the "relevant commercial activity" may relate to goods and services that differ from the economic market in which the competition concern arises.

The CMA's new wait and see approach to global mergers

The Guidance includes updates that respond to recent criticism of the CMA for intervening in mergers which appear to have limited impact on the UK. The Guidance confirms that the CMA is more likely to prioritise those mergers that have a UK-specific market impact to ensure that it meets the objective of proportionality.

In respect of exclusively global (or broader than national) markets, the CMA may adopt a "wait and see" approach. In summary, where investigations are being undertaken by competition authorities in other jurisdictions and there is a reasonable chance that the test for a reference to a phase 2 investigation would be met, the CMA will be less likely to undertake its own investigation in cases where remedies that are agreed or imposed in other jurisdictions would also be likely to address any competition concerns in the UK. Additionally, the Guidance states that where the CMA has adopted this approach, it will ask the merger parties to keep the CMA updated on the progress of these proceedings. Where the parties have not notified the CMA of an exclusively global merger, the CMA can, as outlined in the MIC Guidance, ask the merger parties to provide information relating to the current status of the proceedings in other jurisdictions, before then deciding whether to open an investigation, or adopt the wait and see approach. Ultimately, there remains little guidance on how the wait and see approach will work in practice and it remains to be seen what practical implications this approach will have, including on the predictability and pace of the CMA's review.

Changes to the CMA's Merger Notice template

The Guidance places an emphasis on the requirement for merging parties to disclose information and internal documents earlier in the process and prior to the formal pre-notification stage. This is also reflected in the amended Merger Notice template. A number of the questions have been amended, including:

• Question 8 of the Merger Notice template (which requests internal documentation directly relating to the merger) now includes a request for the provision of the parties' documents relating to the decision making process, the anticipated timeline, and key internal contacts involved in the proposed merger. This request is applicable from the initial conception of the merger to the point at which final agreement is reached. Previously, the case team often requested information on how the merger was agreed and approved during the pre-notification stage, whereas the Guidance now requires that this information will be submitted by the merging parties in their draft Merger Notice template (i.e. prior to pre-notification discussions).
• Secondly, Question 9(b) requests copies of all internal documents that set out competitive conditions (i.e. market conditions, the parties' market shares, other competitors and relevant business plans). Previously this requirement only applied to horizontal overlaps between the merging parties, whereas the amended Guidance now also includes vertical and adjacent relationships. In respect of the de minimis threshold for when parties are not required to submit documents in response to this question, the Guidance distinguishes between horizontal overlaps and vertical / adjacent relationships. While the updated Merger Notice template retains the 15% threshold for horizontal overlaps, it has introduced a new threshold of 30% for vertical / adjacent relationships.
• Question 15 has been expanded from a standard request for the parties' bidding data that showed any historic bids in the relevant overlapping markets. The amendments to question 15 seek to understand (i) the significance of potential opportunities compared with their revenue, (ii) the frequency at which these opportunities arise, and (iii) the variation in value between potential opportunities. The CMA is expanding question 15 in an attempt to narrow down the appropriate scope of its analysis to what is relevant for the investigation.

Comment

The CMA's Guidance largely adopts the changes that were proposed in the consultation, but includes a small number of important changes following stakeholder feedback. Perhaps the most significant change, which was also most frequently raised by stakeholders, relates to Question 9(b) of the Merger Notice template (outlined above). The consultation had originally reduced the de minimis threshold for when parties are not required to submit internal documents in response to this question from a share of supply not exceeding 15% to 10% (for both horizontal overlaps and vertical / adjacent relationships). The reinstatement of the 15% threshold for horizontal overlaps and the revised 30% threshold for vertical and adjacent relationships is a welcome decision.

From a consultation aimed at updating the CMA's leniency policy (see our November 2025 update) to opening the door to greater, and more frequent behavioural remedies (see our October 2025 update), the amendments to the CMA's merger procedural guidelines are just the latest in a growing list of changes to its regulatory environment that the CMA has been exploring this year in applying the 4Ps throughout its case work.

Want to know more?

• Consultation outcome: refining the UK subsidy control regime, 17 April 2025, https://www.ashurst.com/en/insights/consultation-outcome-refining-the-uk-subsidy-control-regime/

• CMA reconsiders approach to merger remedies and publishes Mergers Charter, 17 March 2025, https://www.ashurst.com/en/insights/cma-reconsiders-approach-to-merger-remedies-and-publishes-mergers-charter/
• CMA consults on further reform to UK merger procedure guidelines, 4 July 2025, https://www.ashurst.com/en/insights/cma-consults-on-further-reform-to-uk-merger-procedure-guidelines/