When Do You Need Competition Authority Approval for a Merger or Acquisition?

Merger control approval is the single most common regulatory gate in global M&A, and misjudging it is one of the most expensive mistakes a dealmaker can make. This guide explains exactly when a merger, acquisition, or joint venture must be notified to a competition authority, what “control” really means, how thresholds work, and what happens to companies that close first and ask later — with real enforcement decisions from the European Commission and other regulators as case studies. It is the cornerstone article of our Global Competition & Antitrust hub.

What is merger control and why does it exist?

Merger control is the system by which competition authorities review mergers, acquisitions and certain joint ventures before they close, to prevent deals that would significantly harm competition. Unlike cartel or abuse cases, it is preventive: the authority intervenes before market structure changes, because unscrambling a merged business afterwards is slow, costly and often impossible.

More than 130 jurisdictions now operate merger control regimes, most modelled loosely on either the US Hart-Scott-Rodino (HSR) Act of 1976 or the EU Merger Regulation (EUMR). The core bargain is the same everywhere: companies get legal certainty through a defined review process, and in exchange they must notify qualifying deals and wait for clearance. That waiting obligation — the suspensory effect or “standstill obligation” — is what makes merger control bite. A deal that is perfectly benign competitively can still attract severe fines purely for skipping the queue.

What counts as a “concentration” that authorities review?

A concentration is any transaction that produces a lasting change of control over a business: a merger of two independent companies, an acquisition of sole or joint control, or the creation of a full-function joint venture. If control does not change on a lasting basis, most regimes have nothing to review — regardless of deal value.

“Control” is broader than a 50% shareholding. It means decisive influence: the ability to determine strategic commercial behaviour. A 30% stake with veto rights over the budget or business plan can confer control; a 60% purely financial stake with no governance rights sometimes does not. Authorities also look at negative control (the power to block strategic decisions), de facto control (a large minority facing dispersed shareholders), and asset deals — buying a factory, a brand portfolio or a customer book can be a notifiable concentration if the assets constitute a business with market turnover.

Joint ventures deserve special care. In the EU and Türkiye, a JV is notifiable when it is full-function: it performs, on a lasting basis, all the functions of an autonomous economic entity — its own management, resources and market access. A pure production or R&D vehicle serving only its parents usually falls outside merger control (though it may still raise cartel-style coordination questions).

When is a filing mandatory — and what actually triggers it?

A filing becomes mandatory when the concentration meets a jurisdiction’s notification thresholds, which are almost always based on the parties’ turnover (revenue), and occasionally on deal value or market share. If the thresholds are met, notification is compulsory even if the parties see no competitive overlap whatsoever.

Three design features determine how a regime behaves in practice. First, whether it is mandatory or voluntary: the UK is the famous voluntary outlier — you may close without filing, but the Competition and Markets Authority (CMA) can investigate and unwind the deal afterwards. Second, whether it is suspensory: in the EU, US, Türkiye and China you must wait for clearance before closing; in a handful of regimes you must file but may close during review. Third, local nexus: most thresholds require some local turnover, but a few (COMESA, historically Türkiye’s worldwide-turnover limb) can technically capture deals with minimal local effect.

For the concrete 2026 numbers in the United States, EU, UK, Türkiye and China, see our companion article on merger filing thresholds compared.

What happens if you close without approval?

Closing a notifiable deal without clearance — or implementing it early through control-like conduct — is called gun jumping, and it is punished harshly. The EU can fine up to 10% of group worldwide turnover; Türkiye imposes a fine of 0.1% of Turkish turnover for failure to notify, plus substantive fines if the deal proves problematic; China’s SAMR now fines up to RMB 5 million even for harmless failures, and more if competition is restricted.

Beyond fines, authorities can declare the transaction legally invalid, order divestment or full unwinding, and in the US seek disgorgement. Gun jumping also poisons the substantive review: an authority that catches you closing early rarely gives you the benefit of the doubt on remedies. We dissect the leading cases — Altice’s €124.5 million fine, Canon’s “warehousing” structure, Illumina — in our dedicated guide to gun jumping and its penalties.

Which deals need approval in more than one country?

Any deal involving groups with meaningful revenue in several countries can trigger parallel mandatory filings — five, ten, even forty. Each regime applies its own thresholds to the same transaction; there is no global one-stop shop. The EU’s “one-stop” principle only prevents EU member states from reviewing a deal that meets EUMR thresholds; the US, UK, China, Türkiye and others still review it independently.

Microsoft’s $69 billion acquisition of Activision Blizzard was examined in more than 40 jurisdictions, cleared unconditionally in most, conditionally in the EU and China, and initially blocked in the UK until the deal was restructured. Coordinating that footprint — aligning timelines, remedy packages and the long-stop date — is a discipline of its own, covered in our article on managing multi-jurisdictional merger filings.

Do below-threshold deals ever get reviewed?

Yes — turnover thresholds are the norm, not a guarantee of safety. Authorities increasingly reach deals that fall below them, especially “killer acquisitions” of nascent rivals in pharma and tech whose revenues are still tiny relative to their competitive significance.

The tools vary. The UK’s share-of-supply test catches deals with zero target turnover. Germany and Austria added deal-value thresholds (€400 million and €200 million respectively). Türkiye removed the local turnover threshold for technology undertakings, so acquiring a Turkish-relevant tech target can be notifiable at any target size. After the EU Court of Justice’s 2024 Illumina judgment curtailed Article 22 referrals of purely below-threshold deals, several EU member states introduced call-in powers allowing their authorities to summon deals for review; national referrals from those regimes can still bring a small deal to Brussels. The practical message: a threshold analysis is necessary but not sufficient — strategic deals need a substantive risk assessment too, a theme we expand in our killer-acquisitions analysis.

How long does merger approval take?

Simple cases clear in four to eight weeks; problematic ones take six to eighteen months. Most regimes run a two-stage process: a Phase I review of roughly 25–40 working days for unproblematic deals, and a Phase II in-depth investigation of four to eight additional months where serious doubts arise. Pre-notification contacts — the informal draft-and-comment period before the clock even starts — routinely add one to three months in the EU.

Timing is strategic, not administrative. Long-stop dates, financing commitments and interest-rate exposure all hang on the slowest jurisdiction in the footprint. Our walk-through of Phase I, Phase II and remedies maps the deadlines regime by regime.

How should dealmakers plan for merger control?

Start the antitrust analysis before the term sheet, not after signing. A competent filing analysis at the letter-of-intent stage shapes everything downstream: the long-stop date, the conditions precedent, who bears the regulatory risk, and whether the seller demands a reverse break fee.

The standard playbook has five steps. Map the parties’ revenues by country and compute every plausible threshold. Classify each jurisdiction as mandatory-suspensory, mandatory-non-suspensory, or voluntary. Assess substantive overlap honestly — market shares, closeness of competition, vertical links. Build the timeline backwards from the slowest expected clearance. And draft deal covenants that keep the parties independent until closing: no integration, no coordination, clean-team protocols for sensitive data. Our antitrust due-diligence guide turns this into a checklist you can hand to a deal team.

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