Market Definition
The process by which competition authorities identify the relevant product and geographic market in which competitive effects are assessed, as part of — but not the sole determinant of — a market study, investigation, or merger review.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
Before the CMA can assess whether competition in a market is working well, it typically needs to frame what that market actually is. Its Markets Regime Guidance explains that 'market definition involves identifying the most significant competitive alternatives available to customers of the goods or services under consideration' — in other words, working out which products and which geographic areas are realistically substitutable from a customer's perspective, so that competitive conditions can be properly assessed.
Crucially, the CMA is clear that defining the market is a tool, not an end in itself: 'while market definition can be an important part of the overall assessment, it is not an end in itself.' The evidence gathered as part of the wider competitive assessment can be at least as important as the formal boundaries of the market, and the CMA's guidance elsewhere confirms it is not always necessary to conclude on a single, formal market definition before reaching a view on competition concerns — the exercise exists to inform the analysis, not to constrain it artificially.
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Official sources
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