This Practice Note outlines the provisions in the Assimilated Registration, Evaluation, Authorisation and Restriction of Chemicals Regulation (EC) No 1907/2006 (UK REACH) that allow a manufacturer of substances, mixtures or articles that are produced outside Great Britain (GB) to appoint an ‘Only Representative’ to assume the registration obligations of customers importing its substances into GB. The note also highlights how a ‘Third Party Representative’ may be appointed by a GB manufacturer, importer or, where relevant, downstream user, to allow them (as a potential registrant or data holder) to remain anonymous vis-à-vis other stakeholders in activities conducted under UK REACH.