The UK CMA updates its merger remedies guidance

Published on 19 December 2025, the updated merger remedies guidance clarifies the tests the Competition and Markets Authority (CMA) will apply when choosing remedies, the risks it will consider, and how parties can improve their chances of acceptance. This forms part of its wider drive to improve its "4Ps" (pace, predictability, proportionality and process), and comes alongside updates to the merger control procedural framework.

Structural versus behavioural remedies

The guidance removes the presumption for structural over behavioural remedies during Phase 1 investigations. Instead, each proposed remedy is assessed against two key criteria:

• Effectiveness: Does the remedy fully resolve the substantial lessening of competition (SLC)? Remedies are more effective if they restore competitive rivalry and address the source of the SLC. Crucially, the CMA no longer needs 'certainty' but must have 'a high degree of confidence'.
• Proportionality: Is the remedy no more onerous than necessary, weighing costs against the SLC and its adverse effects? Costs include distortions in market outcomes, monitoring and compliance burdens, and loss of relevant customer benefits (RCBs). If multiple effective remedies exist, the CMA must choose the least onerous. If no fully effective remedy is proportionate, it may consider partially effective remedies, or even no remedies.

In practice, structural remedies remain more likely to meet these criteria than behavioural remedies. However, the guidance notes that enabling remedies may have similar effects to structural remedies. Enabling remedies remove obstacles to competition and stimulate rivalry (for example, intellectual property licensing or use of assets for competitors), in contrast to controlling remedies, which regulate outcomes (such as price caps).

The guidance also confirms that the CMA may take RCBs into account when assessing undertakings-in-lieu (UILs) at Phase I; when deciding whether to refer to Phase 2; and in Phase II proportionality assessments.

Additional guidance on effectiveness: structural remedies

The guidance provides more detail on divestiture risks, particularly "composition risks". Carve-outs must be adequately specified and should not cause the loss of economies of scale, create difficulties in transferring customers, or split assets in a way that harms competitive potential. The CMA should generally opt to divest a business including IP rights rather than impose an IP-licensing remedy.

In Phase I mergers concerning local markets, the CMA may accept the divestiture of local sites where there is a localised SLC, provided effectiveness is robustly evidenced.

To mitigate risks from complex structural remedies, parties should: engage early with the CMA and customers; appoint an independent expert or monitoring trustee; propose alternative "fall-back" divestiture remedies; or identify an upfront purchaser.

Additional guidance on effectiveness: behavioural remedies

For behavioural remedies to address an SLC, the CMA will consider specification risks (clarity on compliance); circumvention risks (whether the remedy addresses all adverse behaviours); distortion risk (whether it disrupts normal competition); and monitoring and enforcement risks.

Monitoring may be mitigated where the industry has its own regulator with enforcement powers, where the remedy aligns with commercial norms, or where stakeholders can report non-compliance.

Controlling remedies are only likely to be applied where there is no other suitable remedy, or to cover a transitional period pending full implementation.

Osborne Clarke comment 

In practice, what this means is that businesses should:

• Engage early. Involve the CMA, purchasers, stakeholders, independent experts or monitoring trustees early, especially when seeking complex structural remedies in the tight Phase I timeline.
• Consider appointing experts. The CMA cannot require parties to appoint an expert or trustee, but voluntary appointments may strengthen their case. Note that merger parties will always pay their remuneration.
• Not assume behavioural is easier. While the CMA now appears more open to behavioural remedies, it is still likely to favour structural remedies unless parties provide strong evidence of effectiveness and proportionality, accounting for the particular risks identified.