Tell the CMA about a merger that might affect you
Source: gov.uk (2025-06-22)

Why the Competition and Markets Authority (CMA) has asked you for information about a merger, and how to share it with us.

The CMA investigates some mergers and assesses how they could affect competition in the UK.

When we investigate a merger, we usually want to hear from:
- the merging businesses’ customers or competitors
- people or businesses with expert knowledge of the relevant products, services or markets
- any other people or businesses that have helpful information
You may have been asked to share information or join a call with us. This page explains why and what you can do next.

Tell the CMA about a merger it is not investigating

Email xxx@xxx.xx (mailto:xxx@xxx.xx) to tell us about a merger that we are not already investigating.

Tell us briefly which merger you are referring to and why you think it could affect competition in the UK.

Tell the CMA about a merger you are involved in. (https://www.gov.uk/guidance/mergers-how-to-notify-the-cma-of-a-merger)

Who we are

The CMA is the independent, non-ministerial government department responsible for keeping markets open and competitive. One important duty we have is to ensure that UK businesses and consumers are not harmed by mergers that would reduce competition. Those harms could include lower quality goods or services, less choice or higher prices.

Why we ask for information

It’s important for the CMA to hear from those who could be affected by a merger, or who understand the markets we’re looking at. This helps us to make well-informed, evidence-based decisions.

This is your opportunity to tell us how you think the merger may affect your business, or competition in your market. We aim to get a fair range of views from different businesses.

We may have received your contact details from the merging businesses, or through our own market research.

How we treat your information

Most of the information we ask you for will not be confidential. If we need to request commercially sensitive information (like sales figures), we will treat confidentiality very seriously and are subject to strict legal obligations.

While we cannot promise to keep the material you provide us confidential in all scenarios, we routinely aggregate data, anonymise quotations and redact parts of our published decisions to protect confidentiality.

We will ask you to identify any information you consider confidential and explain why.

Read Transparency and disclosure – statement of CMA’s policy and approach (CMA6) (https://www.gov.uk/government/publications/transparency-and-disclosure-statement-of-the-cmas-policy-and-approach) (in particular chapter 4, paragraph 4.27 onwards) to find out more about how the CMA protects confidential information.

Join a call with us

If you are a customer of or compete with either of the merging businesses, the CMA might ask you to join a phone or video call to discuss the merger.

In the call we’re likely to ask you general questions about your market, and more specific questions about your products or services. We will likely also ask you questions about the products or services offered by the merging businesses, and alternatives to those products or services.

If we have a specific topic or product/service that we want to discuss, we will let you know before the call.

Respond to a request for information

The CMA might email you a set of questions it would like you to answer. We call this a ‘request for information’ (RFI). The sort of questions we ask varies according to the nature of the merger, and how far along our investigation is at this point.

To respond to the RFI, email your answers to the CMA case team. Their contact details should be in the RFI, and you can ask to speak to them first if you have questions.

Respond by the deadline in the RFI. Let the case team know as soon as possible if you think you will need more time.

We might ask you for data or documents to support your answers. If we do, we will tell you if we need them in a specific format.

Do I have to respond?

An RFI is usually voluntary, but responding will help us to make an informed decision that’s best for UK businesses and consumers.

However, the CMA does have legal powers to gather information that’s relevant to a merger (for example, using a ‘section 109 notice’). We will tell you if you are legally required to answer our questions, in the format we ask for and by the deadline we set.

Either way, you must answer our questions truthfully. Tell us if you do not know the answer or do not have the information we ask for.

It also helps us to know if an answer is based on:
- an internal estimate
- internal market knowledge
- publicly available information
Read our guidance on our jurisdiction and procedure (https://www.gov.uk/government/publications/mergers-guidance-on-the-cmas-jurisdiction-and-procedure) (from paragraph 9.12) and statement of policy on our approach to administrative penalties (https://www.gov.uk/government/publications/administrative-penalties-statement-of-policy-on-the-cmas-approach) to find out more about our information gathering powers.

Respond to an invitation to comment

When the CMA reviews a merger, it will ask for views publicly. We do this by publishing an ‘invitation to comment’ (ITC) on the merger case page. We also publish a notice on the Regulatory News Service (RNS).

Find all our open merger cases (https://www.gov.uk/cma-cases?case_type%5B%5D=mergers&case_state%5B%5D=open).

We are interested in your views on whether the merger is expected to substantially affect competition.

Email the CMA case team to respond to an ITC. The case page includes their email address and the deadline for responses.

Find more information

Read our other guidance for businesses involved in a merger investigation (https://www.gov.uk/government/collections/information-for-businesses-involved-in-a-merger-investigation).

Learn more about internal documents requested during an investigation (https://www.gov.uk/government/publications/internal-documents-in-merger-investigations).