How the CMA investigates competition and consumer issues

Guidance about our processes for investigating competition and consumer issues in markets.

The Competition and Markets Authority (CMA) investigates mergers and anti-competitive practices in markets and can enforce a range of consumer protection legislation. We derive most of our powers from the Enterprise Act 2002 (EA02) and the Competition Act 1998 (CA98).

Mergers and markets are investigated initially at phase 1, but can be escalated to more in-depth phase 2 investigations. Decisions on merger and market inquiries referred for phase 2 investigation are taken by independent groups of panel members.

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)


  1. How the CMA handles information and complaints about businesses
  2. CMA Prioritisation Principles
  3. Procedural Officer: raising procedural issues in CMA cases
  4. Administrative penalties - the CMA’s approach: CMA4
  5. Transparency and disclosure - statement of CMA’s policy and approach: CMA6
  6. Concurrent application of competition law to regulated industries: CMA10
  7. Variation and termination of undertakings and orders: CMA11
  8. Transitional arrangements - CMA's proposed approach: CMA14
  9. Rules of procedure for merger, market and special reference groups: CMA17
  10. CMA’s approach to short-form opinions: CMA27

Competition Act 1998 and cartels

Under the CA98, we’re responsible for investigating where there may be breaches of UK or EU prohibitions against anti-competitive agreements and abuses of dominant positions. We’re also responsible for bringing criminal proceedings against individuals who commit the cartel offence under the EA02.


Under the EA02, we conduct market studies and investigations to assess particular markets where there are suspected competition problems. We can require market participants to take steps to address these problems.


Under the EA02, we investigate mergers that could potentially give rise to a substantial lessening of competition. We can specify measures that the merging parties must take to prevent or unwind integration between them while the investigation takes place.

Regulatory appeals and references

We conduct regulatory appeals and references in relation to price controls, terms of licences or other regulatory arrangements under sector specific legislation (gas, electricity, water, post, communications, aviation, rail and health).

  1. Energy code modification rules: CC10
  2. Energy code modification cases appeals: CC11
  3. Energy licence modification appeals rules: CMA70
  4. Energy licence modification appeals guide for participants: CMA71
  5. Postal services price control appeals rules: CC16
  6. Postal services price control appeals: CC17
  7. Airport licence condition appeal rules: CC19
  8. Airport licence condition appeal rules for participants: CC20
  9. National tariff methodology reference rules: CC21
  10. National tariff methodology reference rules for parties: CC22
  11. Telecoms price control appeals guidance for participants: CMA72
Published 25 September 2014