Recent developments in the UK merger control and antitrust regimes

This year has seen significant reforms to the UK merger control and antitrust regimes. The CMA has also recently introduced procedural reforms to improve its overall approach to mergers and is currently consulting on proposed changes to its mergers guidance on jurisdiction and procedure.

2025 has been a year of reform for the UK merger control and antitrust regimes. The Digital Markets, Competition and Consumers Act 2024 (“DMCCA”), which came into force earlier this year, introduced the most significant reforms to the UK competition law landscape since the Enterprise Act 2002 – from enhanced antitrust enforcement powers and the introduction of a new digital markets competition regime to revised merger control rules. In addition, in response to the UK government’s draft Strategic Steer to the Competition and Markets Authority (“CMA”), the CMA has introduced procedural reforms aimed at driving economic growth, including four principles which will underpin its merger control work (“4Ps”).

We take a look at some of the key merger control and antitrust enforcement reforms below, including what this means for businesses and investors.

1. The DMCCA

a) Revised merger control thresholds

The DMCCA introduced revised merger control thresholds for completed mergers where completion took place on or after 1 January 2025 and for anticipated mergers where the formal Phase 1 investigation commences on or after 1 January 2025.

The new merger control thresholds are as follows:

• Turnover test – the turnover test increased from £70 million to £100 million. This means the CMA will have jurisdiction to review a transaction where the enterprise being acquired has a UK turnover exceeding £100 million.
• Hybrid test – the CMA will have an additional power to review transactions where one party has an existing share of supply of goods or services in the UK (or substantial part of the UK) of at least 33% and UK turnover of at least £350 million, provided that the other party (e.g. the target) has a UK nexus.
• Safe harbour – the share of supply test will have a de minimis safe harbour exemption where the annual UK turnover of each of the merging parties is less than £10 million. Subject to new the safe harbour, the pre-existing ‘share of supply test’ will continue to apply. This means the CMA has jurisdiction to review a transaction where it results in the creation of, or increase in, a 25% or more combined share of sales or purchases in (or in a substantial part of) the UK, of goods or services of a particular description. The safe harbour is intended to reduce the regulatory burden on parties where their presence in the UK is limited.

The new hybrid test brings into the scope of the regime transactions which were not previously caught or which the CMA would struggle to assert jurisdiction over. In particular, the hybrid test captures all types of mergers (horizontal, vertical, or conglomerate mergers) whereas the share of supply test only captures horizontal mergers. The hybrid test is acquirer-focused and will typically capture transactions where the acquirer meets both the 33% share of supply and the £350 million turnover thresholds. It is intended to capture the so-called ‘killer acquisitions,’ where larger incumbent companies acquire smaller promising competitors. This might it make it easier for the CMA to assert jurisdiction over transactions involving a target company with limited scale or presence in the UK.

Investors looking to acquire UK companies or assets, no matter the size, should be aware of the new thresholds and consider engagement with the CMA where appropriate.

b) Expedited Phase 2 merger process

The DMCCA introduced a formal fast track procedure for making Phase 2 references. Merging parties can submit a fast-track reference request during the pre-notification period or at any time before the end of the Phase 1 investigation (which lasts up to 40 working days) without having to concede to an adverse Phase 1 decision. This will enable investigations to be concluded more quickly than would otherwise be the case. Where the CMA has accepted a fast-track reference request, it will also be able to extend the Phase 2 deadline to provide flexibility where required. The fast-track procedure will not apply to water mergers or energy network mergers, which have their own regimes.

c) Antitrust enforcement powers

The DMCCA strengthens the CMA’s powers to investigate and enforce competition law as follows:  

• Extraterritorial reach: The Chapter I Prohibition of the Competition Act 1998 prohibits agreements or concerted practices between undertakings, or decisions by associations of undertakings, which have the object or effect of restricting, preventing or distorting competition. The Chapter I Prohibition now also applies to such agreements and practices which are implemented outside the UK, provided they are likely to have “an immediate, substantial and foreseeable effect on trade within the United Kingdom”. The CMA also has the power to issue information requests to entities located outside the UK which will potentially expand the reach of its investigations to international cartels.
• Dawn raids: Where the CMA obtains a warrant to conduct an unannounced inspection at business or domestic premises (known as a “dawn raid”), the CMA now has the power to request the production of information that is stored electronically and is accessible from the premises. This gives the CMA the power to request access to Cloud storage platforms for example, or other electronic platforms that are not onsite.
• Domestic dawn raids (seize and sift): The CMA now has the power to seize and sift documents when conducting dawn raids at domestic premises. This is increasingly important in the context of working from home and matches the power the CMA has when conducting dawn raids at business premises.
• Preservation of documents and interviews: Where an individual knows or expects that an investigation will occur, the DMCCA imposes an obligation on that individual to preserve documents where they know or suspect that those documents would be relevant to the investigation. In addition, during an investigation, the CMA now has the power to interview individuals remotely and to interview individuals who are not connected to the company being investigated (i.e. those who are not employed by the company or concerned with the management or control of the company)provided this is relevant to the investigation.
• Fines – Failure to comply with CMA investigations or information requests can now lead to a fixed fine of up to 1% of an undertaking’s global turnover or a daily rate of up to 5% of the undertaking’s daily global turnover. The CMA was previously only able to fine companies a fixed fine of up to £30,000 and a daily rate of £15,000. The CMA also now has the power to impose civil fines on individuals and can impose a fixed fine of up to £30,000 or a daily rate of £15,000 for failure to comply with an investigation.

The combination of these new powers will strengthen the CMA’s ability to investigate potential breaches of competition law and enforce the rules. Companies subject to investigations should be aware of the scope of the CMA’s investigation powers so as to avoid potential penalties for non-compliance.

d) New Digital Markets Competition Regime

The DMCCA introduced a new digital markets competition regime which gives the CMA new functions related to the regulation of competition in digital markets. Under the new regime, the CMA has the power to designate companies with Strategic Market Status (“SMS”) in relation to a particular digital activity (e.g. the provision of a service by means of the internet, or the provision of one or more pieces of digital content linked to the UK) where certain jurisdictional conditions are met. The CMA has the power to impose conduct requirements on SMS companies and to introduce pro-competition interventions with the aim of achieving positive outcomes for UK consumers and businesses. 

In addition, the SMS company will have an obligation to report planned mergers or acquisitions to the CMA prior to completion where they have a value of £25 million or more and a UK connection. The CMA has significant powers to investigate and enforce the new regime and has launched two SMS designation investigations since the regime came into force (the first investigation is looking into Google’s general search and search advertising services (the CMA is currently consulting on its proposed decision to designate Google as having SMS in general search services) and the second investigation is looking into Google and Apple’s mobile ecosystem services). However, the CMA announced that it expects to open three to four SMS investigations within the first year of the regime coming into force so it is likely there will more investigations launched this year.

2. CMA merger procedural reforms

In addition to changes introduced by the DMCCA, the CMA has recently introduced a number of procedural reforms aimed at updating and improving its approach to mergers. Having obtained feedback from businesses and investors, and in response to the UK government’s draft Strategic Steer to the CMA, the CMA announced procedural reforms in February 2025 aimed at driving economic growth, and business and investor confidence. In particular, the CMA announced the 4Ps which will underpin is approach to UK merger processes and issued a consultation on 20 June 2025 on its draft updated guidance on jurisdiction and procedure which seeks to embed the 4Ps. The 4Ps and updated process reflected in the draft guidance are as follows:

• Pace – the CMA has introduced a new KPI to announce merger clearance decisions for straightforward Phase 1 cases by working day 25 (down from the current average of 35 working days). The CMA has also introduced a new KPI to complete the pre-notification phase within 40 working days (against the 2023/24 average of 65 working days and the 2024/25 average of 71 working days). In order to achieve this:
  • the CMA expects that the initial draft merger notice provided by parties during the pre-notification phase will include initial responses to the questions in the draft merger notice, all supporting documents requested in the notice, all third party contact details requested in the notice and consent for the CMA to publish on its website details of the transaction and the fact that it will be commencing pre-notification and contacting third parties. The CMA will not be able to commence the 40-working day KPI without receiving this information upfront;
  • the CMA also plans to engage with merging parties more during the pre-notification phase including having teach-in sessions for the case teams and informal update calls;
  • the CMA will implement the pre-notification KPI for initial draft merger notices received after 20 June 2025.
• Predictability – in order to strengthen business certainty about which deals might attract the CMA’s attention, the CMA is consulting on the revised draft guidance on jurisdiction and procedure which is aimed at clarifying how the CMA approaches the ‘share of supply’ and ‘material influence’ tests;
• Proportionality – in March 2025, the CMA launched a review of its approach to merger remedies aimed at reviewing its overall process, taking a proportionate approach to international mergers and looking at how it can strike the right balance between different types of remedies. The CMA stated that its objective is for as many of the deals as possible which raise competition concerns to be cleared with effective remedies, rather than be prohibited.
• Process – in March 2025, the CMA published its Mergers Charter which sets out its commitment to the 4Ps, as well as laying out what will be needed from the CMA, businesses and advisors to ensure the success of this new approach. This should allow transactions to be reviewed more efficiently and provide more transparency and confidence to investors.

How can we help?

Burges Salmon has significant experience advising UK and international companies on UK merger control, antitrust rules and antitrust investigations. If you have any questions in relation to the issues raised in this article, please contact Chris Worrall or your usual Burges Salmon contact.

This article was written by Sandra Mapara.