Short answer: many UK mergers do not have to be notified, but the CMA may review a transaction that satisfies any route in section 23 of the Enterprise Act 2002: target UK turnover exceeding £100 million; a share-of-supply test that creates or increases a share to at least 25%, with at least one enterprise concerned having UK turnover above £10 million; or the hybrid test, under which one enterprise concerned has at least a 33% UK share of supply and UK turnover above £350 million and another enterprise has a UK nexus. A designated SMS firm has a separate pre-completion reporting duty when an event crosses the 15%, 25% or 50% qualifying-status thresholds, or forms a qualifying joint venture, and the consideration condition of at least £25 million is met. See Enterprise Act 2002, section 23 and DMCC Act 2024, sections 57 and 58. Last updated 18 July 2026.

The regulatory framework

UK merger control is voluntary and non-suspensory for most parties: there is no obligation to notify, but the CMA can review a qualifying merger before or after completion. A merger qualifies for review where it gives rise to a relevant merger situation under the Enterprise Act 2002, and the CMA then assesses whether it results, or may be expected to result, in a substantial lessening of competition (section 22). That substantial lessening of competition test is unchanged for digital deals; what changed on 1 January 2025 was the jurisdictional thresholds that bring a deal within reach.

The DMCC Act 2024 amended section 23 of the Enterprise Act. The target-turnover test now requires UK turnover exceeding £100 million. The share-of-supply route requires a merger-created or enhanced share of at least 25% and UK turnover above £10 million for at least one enterprise concerned. The hybrid route applies where one enterprise concerned has at least a 33% UK share of supply and UK turnover exceeding £350 million, and another enterprise has the required UK nexus. The small-merger protection means no relevant merger situation arises where none of the enterprises concerned has UK turnover above £10 million.

Does my deal need CMA clearance?

A digital or technology transaction can fall within CMA jurisdiction by any one of three routes. The table below sets them out. Because market definition in digital infrastructure can be local rather than national, the share-of-supply tests can be met even where a national share looks modest, so the analysis has to map real overlaps rather than headline figures.

Route to jurisdiction	Test	Source
Target turnover	Target UK turnover exceeds £100 million	Enterprise Act 2002, section 23(1)
Share of supply	Merger creates or enhances a UK share of supply of at least 25%, and at least one enterprise concerned has UK turnover above £10 million	Section 23(2) to (4)
Hybrid	One enterprise concerned has at least a 33% UK share of supply and UK turnover above £350 million; another enterprise has a UK nexus	Section 23(4C) to (4G)
Small-merger protection	No relevant merger situation where none of the enterprises concerned has UK turnover above £10 million	Section 23

What extra rules apply to firms with strategic market status?

A firm designated with strategic market status under Part 1 of the DMCC Act has a separate pre-completion reporting duty. Under sections 57 and 58, a reportable share or voting-rights event crosses from below 15% to at least 15%, from 25% or less to more than 25%, or from 50% or less to more than 50% in a UK-connected body corporate, with total consideration of at least £25 million. A qualifying joint-venture formation is also reportable. Once the CMA accepts a sufficient report, a five-working-day waiting period applies under section 63.

Why merger control matters for your deal

Merger review drives deal certainty and timing. A voluntary regime does not mean a safe one: the CMA can call in a completed deal and, in the meantime, impose an initial enforcement order that freezes integration. Parties near the thresholds routinely manage that risk through pre-notification discussions, and can now request a fast-track reference straight to a Phase 2 investigation where significant issues are likely, avoiding a Phase 1 clearance step. Merger review also runs in parallel with, and separately from, national security screening under the National Security and Investment Act 2021, which imposes its own mandatory notification in sensitive sectors including communications and data infrastructure. Clearance under one regime cannot be assumed from the other. Reading the competition and national security positions together, early, is what keeps a digital-sector deal on track.

How we work

We work with clients in three ways: as direct legal advisers on a specific question, as specialist co-counsel alongside a corporate team, and as fractional general counsel on a retained basis. Rob Bratby currently holds four fractional General Counsel appointments, at The One Touch Switching Company, TelXL, Core Communication and the UK Payments Initiative, giving direct insight into how regulated businesses are bought, sold and integrated. On a transaction, we read the deal and the regulation together, so competition and national security clearances are handled as part of the deal rather than discovered late in it. This work connects closely with our transactions practice.

Frequently asked questions about merger control in digital markets

Do I have to notify the CMA before completing a deal?

For most parties, no. UK merger control is voluntary, so there is no general obligation to notify and no automatic standstill. But the CMA can review a qualifying deal after completion and freeze integration while it does, so parties near the thresholds usually notify or hold pre-notification discussions to secure certainty.

What is the new acquirer-foothold threshold?

The hybrid test is a jurisdictional route added by the DMCC Act 2024. It is met where one enterprise concerned supplies or acquires at least 33% of goods or services of a description in the UK or a substantial part of it, that enterprise has UK turnover exceeding £350 million, and another enterprise concerned has the statutory UK nexus. It does not require an overlap or increment in the 33% share.

What extra obligations apply if a party has strategic market status?

A designated SMS firm must report before completion when a UK-connected acquisition crosses the 15%, 25% or 50% qualifying-status thresholds and total consideration is at least £25 million. A qualifying joint-venture formation can also be reportable. The event cannot take place until the CMA has accepted a sufficient report and five working days have elapsed, unless the CMA consents otherwise.

How does CMA review interact with national security screening?

They are separate regimes with separate triggers and timetables. The National Security and Investment Act 2021 imposes mandatory notification in sensitive sectors, including communications and data infrastructure, and clearance under it cannot be inferred from CMA clearance. A digital-sector deal can require both, and both need to be planned into the timetable.

Also see

Explore our related Digital Regulation pages on SMS Designation and Conduct Requirements, Market Investigations and Studies, Concurrent Competition Powers and Competition Enforcement and Litigation, or return to the Digital Regulation hub. This work connects with our Transactions, Telecoms Regulation and Payments Regulation practices. For commentary on current developments, see our Insights.