Market abuse
MARAlso called market Abuse Regulation, UK MAR
Market abuse covers insider dealing, unlawful disclosure of inside information and market manipulation. The EU Market Abuse Regulation, and its UK equivalent, prohibit these behaviours and require issuers to disclose inside information promptly, keep insider lists and report manager transactions, while firms must detect and report suspicious orders and trades.
How it works
Investment firms and trading venues run trade and communications surveillance to spot patterns such as spoofing, layering, front running or trading ahead of announcements. Suspicious activity is reported to the regulator through a suspicious transaction and order report. Issuers maintain insider lists, control disclosure of inside information and enforce closed periods for managers before results.
MAR matters because it applies to anyone dealing in instruments on EU or UK venues, not only regulated firms. Breaches can lead to fines, bans and criminal prosecution under national law. The EU Listing Act changed disclosure rules from 5 June 2026, so issuers no longer disclose intermediate steps of a protracted process, though the information can still be inside information.
The rules
Prohibits insider dealing, unlawful disclosure and market manipulation, and sets disclosure, insider list and suspicious order reporting duties.
Issuers, investment firms, trading venues and all persons trading EU instrumentsKeeps the MAR prohibitions and duties in UK law after Brexit, supervised and enforced by the FCA.
Issuers, firms and persons trading UK instrumentsEnds disclosure of intermediate steps in protracted processes and replaces the not misleading delay condition with consistency with the latest public announcement.
Issuers with instruments on EU venuesCommon questions
What counts as inside information under MAR?
Inside information is precise information that has not been made public, relates directly or indirectly to an issuer or financial instrument, and would be likely to have a significant effect on prices if it were made public.
What is a STOR?
A suspicious transaction and order report is the report that firms and trading venues send to their regulator when they reasonably suspect an order or transaction could amount to insider dealing, market manipulation or an attempt at either.
Does UK MAR still match EU MAR?
Both started from the same text, but they have diverged. The EU amended MAR through the Listing Act, with disclosure changes applying from 5 June 2026. UK changes are made separately by HM Treasury and the FCA.
