Produced with input from Rebecca Cousin of Slaughter and May on market practice. This Practice Note summarises the rules and guidance in relation to parties who are, or may be presumed to be, acting in concert for the purposes of The City Code on Takeovers and Mergers (the Code). In particular the note considers the different relationships that may qualify as acting in concert, the significance of concert parties in relation to Rule 9 of the Code, and disclosures in relation to stakebuilding. Acting in concert is not prohibited by the Code, but can have significant implications. The consequences of being a member of a concert party will generally bite under Rules 4 (Restrictions on dealings), 5 (Timing restrictions on acquisitions), 6 (Acquisitions resulting in an obligation to offer a minimum level of consideration), 8 (Disclosure of dealings and positions), 9 (The Mandatory offer and its terms) and 11 (Nature of consideration to be offered) when any of the relevant parties acquires shares. All persons to whom the Code applies (and their advisers), including parties to a takeover