Tell the CMA about a competition or market problem

How to notify the CMA if you think competition law might have been broken or you're concerned there’s a problem in a market sector.

What to tell us about and why

Competition law protects businesses and consumers from anti-competitive behaviour, which is illegal. It also protects consumers and businesses from being ripped off.

Please let the Competition and Markets Authority (CMA) know if you have any details about:

The way you report anti-competitive activity depends on the type of activity. Some common examples of anti-competitive activities by businesses, and ways you can report them, are listed below.

Reports from consumers and businesses about anti-competitive behaviour or problems in markets are vital in helping the CMA to ensure that consumers and businesses are getting a fair deal.

Your information is one of the main ways that we get the intelligence that leads us to investigate businesses that may be breaking the law.

If you’re a business, more advice on how you can avoid and report anti-competitive behaviour and avoid unfair terms in sales contracts is available.

Consumer issues that the CMA can’t help you with

The CMA can’t respond in detail to individual complaints.

The law protects your consumer rights when you buy goods or services. Find out who to contact for consumer protection advice and to make a complaint about a product or service.

If you think advertising rules have been broken you can complain to the Advertising Standards Authority.

NHS Improvement is the sector regulator for health services in England. Details of how to complain about a healthcare provider are on its webpages.

The Financial Conduct Authority (FCA) deals with enquiries about the regulation of consumer credit.

Businesses agreeing not to compete with one another (‘cartels’)

This is one of the major types of anti-competitive activity by businesses that you can report to the CMA. A cartel is where 2 or more businesses agree not to compete with each other. It covers the following types of activities:

  • Price-fixing - businesses must not discuss the prices they’re going to charge their customers with their competitors.
  • Bid-rigging - businesses can’t discuss bids for a contract tender with their competitors.
  • Market-sharing - businesses can’t agree to share markets or customers.
  • Sharing information - information can’t be shared between businesses that might reduce competition between them (eg information about prices or suppliers).

Find out more about cartels on the stop cartels page.

Contact the CMA about a cartel

Contact the CMA’s cartels hotline if you want to report information about a cartel.


Call: 0800 085 1664 or 020 3738 6888

You may get a financial reward for information that leads to an investigation.

Apply for leniency if you or your company have been involved in a cartel.

Call: 020 3738 6833

Find out about call charges

Businesses abusing their ‘dominant position’

This is another major type of anti-competitive activity by businesses that you can report to the CMA.

A business might have a ‘dominant position’ in the market if:

  • it has more than a 40% market share
  • it’s not affected by normal competitive restraints

It might be abusing a dominant position if it’s unfair to its customers or other businesses.

Complete our notification form and email it to the CMA to tell us about anti-competitive activity that you have concerns about.

Other anti-competitive activities

Other activities that break competition law and can be reported to the CMA, include businesses:

  • buying or selling jointly with their competitors
  • agreeing with their competitors to reduce production of something to raise its market value
  • restricting how much other businesses can sell their product for
  • agreeing with competitors not to sell to certain customers or deal with certain suppliers
  • having long-term exclusive contracts with any customers or suppliers

Complete our notification form and email it to the CMA to tell us about anti-competitive activity that you have concerns about.

Problems in a market sector

We also want to know if you have had issues with a particular market for goods or services.

When markets are working well, firms compete to win business by achieving the lowest level of cost and prices, developing better products and services or exploiting their strengths, skills, and other advantages to meet consumers’ needs more effectively than their rivals.

This encourages innovation and provides consumers with increased choice. Competition is enhanced when consumers are empowered to shop around through access to readily available and accurate information about products and services.

Markets that are not working well can result in negative effects for consumers, businesses and the economy. For example:

  • consumers may be unable to make informed choices about prospective purchases
  • businesses may be deterred from improving their products or entering the market
  • productivity in the sector may be undermined

Complete our notification form and email it to the CMA to tell us about issues in a market sector that you have concerns about.

Report your concerns to an industry regulator

You can also report concerns about anti-competitive activity in certain sectors to a regulator. These are:

What the CMA will do next

Guidance on how the CMA handles information and complaints we receive about businesses and business practices is available.

We’ll review all the information you send us and acknowledge receipt of your completed forms or emails.

Please note that we can’t respond in detail to individual complaints. We won’t normally enter into correspondence about our decisions on whether to give detailed consideration to the complaints we receive.

As a result of your information we may:

  • contact businesses to remind them about complying with competition and consumer protection law
  • investigate and take legal action against businesses we suspect are breaking competition or consumer protection law
  • conduct studies or investigations into markets where there may be competition and consumer problems
  • prosecute people involved in cartels


If you’re worried about your identity being revealed and you’re contacting us to tell us about a competition or market problem, or are concerned about a merger, tell us in writing when you contact us. You can also make a complaint anonymously using a non-name-based email account, a private masked phone number, by post or via a representative (such as a trade association). In any case, we aim to keep your identity private while we look at the information you provided or the issue you have raised and decide on the best course of action to take.

If we decide to open a formal enforcement case, or rely on information you’ve provided in our investigation of a merger we may then need to reveal your identity and the information that you’ve provided (although in a Competition Act case we’ll aim not to reveal a complainant’s identity without their consent until after a ‘Statement of Objections’ is issued). Therefore, if you’re submitting a complaint anonymously, you should avoid including information that could allow someone to guess your identity.

This is to allow the business being investigated to respond properly to the information provided. Before revealing your identity or the information you’ve provided, we’ll contact you and give you an opportunity to comment on this.

If you’re an individual and you want to give us information about cartel activity, you should contact our cartels hotline. We recognise that many individuals may only be prepared to provide information if there’s a guarantee that their identity as a ‘whistle-blower’ will not become known to third parties. If this applies to you, you should mention this when you call and specially trained officers, mostly with a law enforcement background, will work with you. They will very carefully safeguard any information you give to protect your identity from disclosure.

Victims code

When the CMA takes part in criminal enforcement work, it acts in accordance with the duties set out in chapter 5 of the code of practice for victims of crime (victims code)

Published 14 January 2016