Market overview

The United Kingdom’s cash equity market is centred on the London Stock Exchange, which runs two distinct venues: the Main Market, a regulated market for listed securities, and AIM, its market for smaller and growing companies. AIM opened on 19 June 1995 and is regulated by the Exchange itself rather than through the statutory listing regime. The Financial Conduct Authority is the listing authority and the conduct regulator. Its UK Listing Rules sourcebook, UKLR, decides who may be listed and on what continuing terms, and the Exchange’s own rulebooks govern how the resulting securities trade.

Read the full overview and sources

Admission to listing has hard gates. The securities must be admitted to trading on a regulated market for listed securities, must be freely transferable, and shares must be fully paid and free of liens. The expected aggregate market value of the securities at admission must be at least 30 million pounds for shares and 200,000 pounds for debt securities, while shares of a closed-ended investment fund or open-ended investment company must reach 700,000 pounds. The FCA may admit securities of a lower value if it is satisfied there will be an adequate market. A sufficient number of shares is taken to have been distributed to the public when 10% of the shares in issue at admission are in public hands.

Listings sit in categories rather than one undifferentiated pool. The equity shares (commercial companies) category, the equity shares (shell companies) category and the closed-ended investment funds category each carry their own continuing obligations, and the FCA may require an issuer in any of them to appoint a sponsor where it sees a possible breach of the listing rules, the disclosure requirements or the transparency rules.

AIM works on a different principle. An applicant must appoint a nominated adviser and an AIM company must retain one at all times. That adviser is responsible to the Exchange for assessing whether the applicant is appropriate for AIM and for guiding the company on its obligations. If an AIM company ceases to have a nominated adviser, the Exchange suspends trading in its AIM securities, and the company has one month to appoint a replacement. Trading in AIM securities runs under the Rules of the London Stock Exchange.

The benchmark family is the FTSE UK Index Series, run by FTSE Russell under ground rules at version 17.2, July 2026. The FTSE 100 holds the largest 100 UK companies by full market capitalisation, the FTSE 250 the next 250 outside it, and the FTSE 350 combines the two. The FTSE SmallCap takes the FTSE All-Share companies too small for the FTSE 350, and the FTSE All-Share aims to cover at least 98% of the full market capitalisation of all eligible companies. Periodic reviews use buffers rather than a single line: a company enters the FTSE 100 if it has risen to 90th or above and leaves if it has fallen to 111th or below, with the equivalent bands for the FTSE 250 set at 325th and 376th.

GSN covers admissions, cancellations and transfers between the Main Market and AIM, FCA rule changes that move the listing gates, index reviews, and issuer announcements released through a regulatory information service.

Sources

This overview is based on the official documents listed below, last checked 2026-09-03. Figures are as stated in those documents.

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