This Practice Note provides an overview of the use of conformity marking in the UK. It explains the purpose and use of conformity markings, the requirements applicable in Great Britain (GB) and Northern Ireland (NI) regarding the use of UK Conformity Assessed (UKCA) and UK Northern Ireland Conformity Assessed (UKNI) marking, the use of Conformité Européenne (CE) marking in the UK, the roles and responsibilities of manufacturers, importers and distributors, the conformity assessment process, marking and labelling requirements, enforcement, and conformity assessment for overseas markets. The main focus of this Practice Note is on conformity marking requirements for products placed on the GB market. Although NI and EU requirements are discussed, this Practice Note does not go into full detail regarding conformity marking requirements in the EU. For a high-level comparison of the conformity marking requirements applicable under the UK and EU product regimes, see Practice Note: Product regulation—UK/EU comparison. What is conformity marking? Conformity marking is a marking placed on a product which shows that the manufacturer believes that the product complies with the applicable legal requirements