A European business expanding into the United Kingdom quickly discovers that the country's competition law system operates with a level of investigative rigour that surprises even experienced in-house counsel. The Competition and Markets Authority (CMA) – the principal competition authority in the United Kingdom – holds broad powers to investigate cartels, scrutinise mergers, and sanction firms whose conduct distorts market competition. Inaction in the face of a CMA investigation, or failure to notify a qualifying transaction, can trigger consequences that are difficult and expensive to reverse.
Competition law in the United Kingdom is governed by domestic competition legislation that prohibits anti-competitive agreements and the abuse of market dominance, and imposes a voluntary-but-consequential merger notification system administered by the CMA. Businesses that breach the prohibitions on cartel behaviour or market dominance abuse face financial penalties calculated as a percentage of annual group turnover, as well as director disqualification and private damages claims. Merger transactions that meet the jurisdictional thresholds may be investigated for up to 24 weeks in a Phase 2 inquiry, with remedies ranging from conditions to full prohibition.
This page sets out the principal instruments available under UK competition law, the procedures and timelines that govern them, the pitfalls most frequently encountered by international clients. Additionally. The cross-border strategic considerations that arise when a business operates between the United Kingdom, Portugal, and the European Union.
The UK competition law system after Brexit
The United Kingdom's departure from the European Union produced a distinct and, in some respects, more demanding competition law environment for internationally active businesses. The CMA no longer participates in the European Commission's one-stop-shop merger review. A transaction that triggers both EU and UK thresholds must now be notified separately to two authorities operating on independent timetables. Practitioners advising on deals with a UK dimension regularly manage parallel reviews, which requires careful sequencing of submissions and consistent economic narratives across two investigations.
Substantive competition law in the United Kingdom is rooted in two central prohibitions drawn from domestic competition legislation: the prohibition on anti-competitive agreements (the Chapter I prohibition) and the prohibition on abuse of a dominant position (the Chapter II prohibition). These prohibitions apply to conduct that affects trade within the United Kingdom. Since the end of the Brexit transition period, the European Commission's precedents no longer bind UK courts or the CMA, though they retain persuasive authority. The Competition Appeal Tribunal (CAT). a specialist court handling competition appeals and damages claims – has begun developing an independent body of UK precedent that diverges in nuanced but commercially significant ways from EU doctrine.
For businesses that have structured their compliance programmes around EU rules, the divergence creates genuine risk. Conduct permissible under an EU block exemption cannot be assumed to be permissible under the equivalent UK retained exemption. The CMA has the power to withdraw the benefit of retained block exemptions in individual cases, a power it has already deployed in specific market contexts. International clients should treat UK and EU compliance as two separate exercises, not a single aligned programme.
The CMA's investigative resources have grown substantially since Brexit. The authority has indicated publicly that it will use its expanded mandate to investigate sectors that were previously reserved for Brussels. Digital markets, data-driven platforms, and pharmaceutical supply chains have all received early attention. A business that previously relied on the European Commission as the sole investigative gateway should expect a more active domestic regulator.
Key instruments: cartels, dominance, and merger control
UK competition law provides three principal enforcement tools. Each carries distinct procedural requirements, timelines, and risk profiles. Understanding the differences is essential before any business decision is made.
Cartel and anti-competitive agreement investigations arise when the CMA suspects that businesses have coordinated on price, output, markets, or customers. The CMA may open a case on its own initiative, in response to a complaint, or following a leniency application. The authority holds wide investigative powers: it can compel the production of documents, require written responses to questions, and conduct unannounced inspections of business premises – commonly known as dawn raids. Obstruction of a dawn raid is a criminal offence. The CMA may also prosecute individuals for the criminal cartel offence, which carries a custodial sentence.
Investigations are lengthy. A complex cartel case can take three to five years from opening to final decision. During that period, the business faces significant management distraction, legal costs, and reputational exposure. The leniency programme (leniency programme) offers immunity or a substantial reduction in penalties to the first participant to disclose a cartel and cooperate fully with the investigation. Timing is critical: the immunity window closes once the CMA has sufficient evidence to proceed without the applicant's cooperation. A business that becomes aware of potential cartel exposure should seek legal advice within hours, not days.
Abuse of market dominance investigations target firms with a dominant position – broadly, a position of substantial market power – that engage in exclusionary or exploitative conduct. Common examples include predatory pricing designed to eliminate a competitor, margin squeeze in vertically integrated industries, and refusal to supply on reasonable terms. The CMA assesses dominance by reference to market share, barriers to entry, and the ability to act independently of competitive pressure. A firm with a substantial share of a narrowly defined market should assess its conduct carefully, because the CMA's view of the relevant market may differ materially from the firm's own commercial understanding.
Penalties for breach of the Chapter I or Chapter II prohibition can reach a significant proportion of annual UK turnover, calculated over the duration of the infringement. The CAT has confirmed that penalties must have a genuine deterrent effect. Directors of infringing businesses may be disqualified from holding office for up to fifteen years. Third parties harmed by anti-competitive conduct may bring follow-on damages claims before the CAT or the High Court (High Court of England and Wales). Either individually or through collective proceedings that function as a form of class action.
Merger control in the United Kingdom is a voluntary system in legal form, but the CMA has the power to investigate completed transactions and impose remedies – including divestiture – even after closing. In practice, transactions that meet the share-of-supply or turnover thresholds are routinely submitted in advance of closing to obtain clearance. The Phase 1 review lasts up to 40 working days. If the CMA identifies a realistic prospect of a substantial lessening of competition, it may open a Phase 2 investigation, which runs for up to 24 weeks and is conducted by an independent inquiry group. Phase 2 decisions carry significant commercial consequences: the group may clear the transaction unconditionally, clear it subject to behavioural or structural remedies, or prohibit it entirely.
A common pitfall for international buyers is underestimating the UK jurisdictional thresholds. The share-of-supply test, which looks at whether the merged entity will supply or acquire a defined category of goods or services to a share of 25% or more in the United Kingdom. Can capture transactions with relatively modest UK revenues. Many cross-border deals are caught by the UK test even where the primary commercial rationale is entirely non-UK. Buyers who close without assessing UK merger control exposure face the risk of a post-closing investigation and a potential requirement to hold separate or unwind completed steps.
For guidance on related corporate processes in the UK, including company formation and governance structuring, see our guide to company formation in the United Kingdom.
To receive an expert assessment of your competition law exposure in the United Kingdom, contact us at info@ferrazwhitmore.com.
Practical pitfalls for international clients
International businesses entering or operating in the UK market encounter a set of recurring difficulties that are not obvious from a reading of the legislation alone.
The first is the assumption that EU clearance resolves UK risk. Since the end of the Brexit transition, EU clearance of a merger or an agreement does not preclude a separate UK investigation. A distribution agreement cleared under the EU Vertical Block Exemption Regulation may require independent UK assessment. A joint venture approved by the European Commission may still require Phase 1 notification in the United Kingdom if the share-of-supply threshold is met. Businesses that operate across both jurisdictions should build a UK competition check into every significant commercial arrangement.
The second pitfall is inadequate document hygiene. The CMA places substantial evidential weight on internal communications. Emails, instant messages, and board presentations that use language suggesting knowledge of competitors' pricing, output intentions, or market strategies can provide the foundation for an investigation even where no formal agreement exists. Many investigations are opened not on the basis of an informant's tip but on materials voluntarily produced in response to a section 26 notice or discovered in a dawn raid. A business whose internal culture allows loose language about competitors takes on measurable legal risk.
The third difficulty is the interaction between competition law and other regulatory regimes. In sectors regulated by the Financial Conduct Authority (FCA) or sector-specific regulators. such as the communications, energy. Alternatively. Water regulators. concurrent competition enforcement powers create the risk of parallel investigation by both the CMA and the sectoral authority. The CMA has developed memoranda of understanding with concurrent regulators, but businesses in regulated sectors cannot assume that a sector regulator will be the only authority examining their conduct.
A fourth, and often underweighted, risk is the exposure of individual executives. The criminal cartel offence does not require proof that the individual knew the conduct was illegal. Prosecutors must establish that the individual agreed with another person to make, implement, or cause to implement certain hard-core arrangements. Director disqualification proceedings under the CMA's civil powers add a further layer of personal risk. International executives posted to the United Kingdom who are unfamiliar with these personal liability rules require targeted briefing, not merely a copy of the group's global competition compliance policy.
Finally, the private damages litigation environment has become materially more active. The CAT's collective proceedings mechanism has produced a significant number of class actions following CMA infringement decisions. Businesses that have been the subject of an infringement finding – even an accepted commitment rather than a formal decision – should assess their exposure to follow-on claims immediately. The limitation period for damages claims can run from the date the infringement decision becomes final, and early assessment of potential claimant bases shapes the strategic response.
International clients facing competition investigations in the UK often encounter related corporate disputes. The firm's practice in corporate disputes in the United Kingdom provides an integrated approach when those matters arise simultaneously.
Cross-border and strategic considerations: UK, Portugal, and the EU
For businesses operating between the United Kingdom and the European Union – including Portugal – competition law generates a distinctive set of cross-border coordination challenges that have intensified since Brexit.
In merger control, the decoupling of the EU and UK review processes means that a transaction with meaningful UK and EU market shares will now face two separate review timetables. Two sets of information requests. Additionally, potentially two different remedy packages. The CMA and the European Commission have developed liaison channels, but their assessments of competitive effects are legally independent. A business that negotiates structural remedies with the Commission cannot assume that the CMA will accept the same package. In practice, the remedy offered in one jurisdiction may limit commercial options in the other. Early modelling of remedy scenarios across both jurisdictions should form part of deal planning before signing.
On the cartel and agreement side. A business operating under a supply or distribution agreement that spans both the United Kingdom and EU member states faces the risk that a single commercial arrangement is assessed by both the CMA and the European Commission. Where the conduct originates or has its primary effects in one jurisdiction, the relevant authority is likely to take the lead, but the other authority retains jurisdiction over effects within its territory. Legal advice obtained in one jurisdiction does not automatically protect the business from liability in the other.
The leniency programme dimension adds further complexity. A leniency application made to the CMA does not automatically extend to the European Commission, and vice versa. Businesses considering leniency in a matter with cross-border effects must assess the position in each affected jurisdiction separately and manage the timing of applications to maximise protection. An application filed too late in one jurisdiction may forfeit immunity while securing it in another. This is among the most time-sensitive decisions in competition law.
Portugal presents a specific consideration for UK-based businesses with Iberian operations. Portugal's competition authority – the Autoridade da Concorrência (Competition Authority of Portugal) – applies EU competition law to conduct affecting trade between member states and national competition law to purely domestic matters. A horizontal agreement between a UK parent and a Portuguese distributor that affects the Portuguese market may be subject to concurrent jurisdiction by the Autoridade da Concorrência and the European Commission. Post-Brexit, the CMA has no formal role in that assessment, but the UK parent's internal documents produced in a UK investigation could be sought by EU or Portuguese authorities through mutual assistance procedures.
Tax and corporate structuring interacts with competition law in ways that are increasingly scrutinised. The His Majesty's Revenue and Customs (HMRC) and competition authorities share intelligence in specific circumstances, particularly where state aid or public procurement matters overlap with competition concerns. A business that relies on a particular tax structure to fund aggressive pricing in a market where it holds a dominant position may face scrutiny from multiple directions simultaneously.
For businesses with Portugal-facing operations, the firm's dedicated competition law practice in Portugal addresses the specific procedural and strategic requirements that apply under Portuguese and EU competition rules.
For a tailored strategy on competition law compliance and risk management in the United Kingdom, reach out to info@ferrazwhitmore.com.
Self-assessment checklist for UK competition law exposure
The following conditions define situations where UK competition law advice is most urgently required. A business that meets one or more of these criteria should seek specialist input before proceeding.
This assessment applies if any of the following are present:
- The business holds a substantial share of supply in any defined UK product or geographic market, particularly if that share exceeds a significant minority of the market.
- The business is party to an agreement with a competitor – whether formal or informal – that touches on pricing, output, market allocation, or customer sharing in the United Kingdom.
- The business is contemplating or has completed a transaction that may meet the UK share-of-supply threshold or the UK turnover threshold for merger review.
- The business operates in a sector subject to concurrent competition enforcement by the CMA and a sectoral regulator (financial services, communications, energy, water, or transport).
- The business has received a CMA information notice, a section 26 notice, or any communication from a competition authority in any jurisdiction referencing conduct that also occurs in the United Kingdom.
Before initiating any engagement with the CMA, verify the following:
- All internal communications relating to the relevant conduct, agreements, or transaction have been preserved under a litigation hold and reviewed by legal counsel.
- The scope of any legal professional privilege attaching to existing advice has been assessed, particularly where documents may be sought by a foreign authority.
- The business has assessed whether a leniency application would extinguish or reduce its penalty exposure, and whether the timing window for immunity remains open.
- Directors and senior managers with personal exposure to the criminal cartel offence or disqualification risk have been separately briefed and advised.
- The cross-border dimension – EU, Portuguese, and any other affected jurisdiction – has been mapped and the relevant limitation periods and notification deadlines identified.
Frequently asked questions
- How long does a CMA merger investigation take, and when must a transaction be submitted?
- UK merger control is voluntary in the sense that there is no mandatory pre-notification obligation, but the CMA may investigate any completed or anticipated transaction that meets the jurisdictional thresholds. A Phase 1 review takes up to 40 working days. If the CMA has concerns, a Phase 2 investigation runs for up to 24 weeks. Parties typically submit before closing to avoid the risk of a post-completion investigation and hold-separate order. Engaging a lawyer in the United Kingdom with experience in CMA procedure at the structuring stage of a deal reduces the risk of jurisdictional surprises.
- Is it a common misconception that small businesses are immune from UK competition law?
- Yes. The Chapter I and Chapter II prohibitions apply to any undertaking whose conduct affects trade in the United Kingdom, regardless of size. The CMA's small agreements exclusion applies only to certain minor horizontal agreements and does not cover hard-core restrictions such as price-fixing or market allocation. A business with a small UK revenue can still hold a dominant position in a narrowly defined market. Directors of small companies are equally at risk of disqualification if they participate in a cartel. Size is relevant to the calculation of penalties, but it does not confer immunity.
- What should a business do immediately if it receives a CMA dawn raid notice?
- The business should not obstruct the inspection or remove or conceal documents – both are criminal offences. Staff should be instructed to cooperate with the inspectors while legal counsel is contacted immediately. The business has the right to take legal advice before complying with a warrant, though inspectors may continue certain steps during that period. Internal communications about the investigation itself should be treated as potentially disclosable. A law firm in the United Kingdom with competition investigation experience should be on standby before any dawn raid risk is identified, not after it materialises.
About Ferraz & Whitmore
Ferraz & Whitmore is an international law firm based in Lisbon, advising business clients across 46 jurisdictions. Our competition law practice supports international businesses in managing CMA investigations, structuring merger notifications, building cartel leniency strategies, and defending dominance cases before the Competition Appeal Tribunal and the High Court. The firm combines English common law expertise with Portuguese civil law tradition, giving cross-border clients an integrated perspective on competition matters that span the United Kingdom, the European Union, and Iberian markets. Our attorneys have advised on competition law matters across civil law and common law systems, and our practice covers 15 areas of law with direct access to EU, UK, and Atlantic regulatory environments. As an international law firm with deep experience in competition law in the United Kingdom, Ferraz & Whitmore provides the strategic and procedural guidance that sophisticated clients require when regulatory exposure is high. To discuss how UK competition law applies to your specific situation, contact us at info@ferrazwhitmore.com.
Disclaimer: This publication is provided for informational purposes only and does not constitute legal advice. The information herein should not be relied upon as a substitute for professional legal counsel tailored to your specific circumstances. Ferraz & Whitmore assumes no liability for actions taken or not taken based on the contents of this material. For advice regarding your particular situation, please contact info@ferrazwhitmore.com.