Information for businesses involved in a merger investigation
Information you may need if your business is part of a merger investigation or affected by one.
The Competition and Markets Authority (CMA) investigates the impact of mergers and assesses how they could affect competition in the UK.
This page includes information and guidance that businesses can refer to and use during a merger investigation.
Find out how the CMA is evolving its approach to mergers, and share your views.
As we carry out our merger reviews, we are committed to 4 principles:
- pace
- predictability
- proportionality
- process
We recognise that mergers and acquisitions activity is strategically important to businesses, investors and the UK economy. All businesses engaging in a merger process should feel listened to by the CMA; understand what we are doing and why; and recognise a sense of fairness and consistent treatment.
We have published our mergers charter, outlining how we will engage with businesses and their advisors during merger reviews.
How the CMA investigates mergers
General guidance on the CMA’s approach to investigating mergers and the process we follow. Start with our quick guide to UK merger assessment.
How to tell the CMA about a merger
The UK’s merger regime is voluntary, which means that you do not have to tell the CMA about a potential merger, but there can be benefits to doing so. Read more about how to notify the CMA of a merger.
The CMA collects information before deciding whether to investigate a merger. Not all mergers are investigated by the CMA.
There are 3 ways we would come to investigate a merger:
- the businesses notify us of the merger
- we investigate on our own initiative
- we hear from other relevant stakeholders
Email the CMA’s mergers team mergers@cma.gov.uk using the merger notice forms below to formally notify a merger to the CMA.
Email the CMA’s mergers intelligence committee mergers.intelligence@cma.gov.uk if you are involved in a potential merger or have concerns about one.
What happens during an investigation
Guidance on what you will need to do during an investigation. The CMA case team will advise further, depending on the circumstances of your potential merger.
Sharing information with the CMA during the investigation
During a merger investigation, the CMA will ask for information from the merging businesses and other relevant stakeholders. Some of these templates and documents may be helpful when you are providing this information.
Updates to this page
Published 31 March 2014Last updated 12 March 2025 + show all updates
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Updated to reflect the CMA's evolving approach to mergers.
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Collection updated.
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Review of NHS mergers: CMA29 added
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First published.