This Practice Note provides high-level information on the key elements of the UK MiFID II regime, with links to detailed guidance. The UK MiFID II regime is a body of law and regulation derived from Directive 2014/65/EU (MiFID II), and including EU measures which had direct effect in the UK, formed part of UK assimilated law upon the UK’s withdrawal from the EU, and are subject to revocation under the Financial Services and Markets Act 2023 (FSMA 2023). Measures forming part of UK assimilated law include Assimilated Regulation (EU) 600/2014 (UK MiFIR) and, until its revocation on 23 October 2025, Commission Delegated Assimilated Regulation (EU) 2017/565 (the UK MiFID II Organisational Regulation). For information on the revocation of UK MiFIR and other assimilated law forming part of the UK MiFID II regime, see Practice Note: UK MiFID II reforms. Activities and firms which the UK MiFID II regime applies to Investment services and activities, and ancillary services The UK MiFID II regime applies to investment services and activities and, where relevant, ancillary services (referred to in the Financial Conduct Authority