CSE2306 - General provisions: can a UK established CSG have members in third countries and can a UK business or organisation belong to a CSG established outside the UK

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No. The exemption only applies to services which a CSG supplies to its members established within the United Kingdom (see CSE4120). With effect from 1 June 2018, the exemption is not permitted where members of a UK established CSG are established in EU Member States.