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HMRC internal manual

VAT Cost Sharing Exemption Manual

How the conditions are to be interpreted: CSGs and VAT groups: How is the 5% test applied to a VAT group member?

If a VAT group member wishes to become a member of a CSG it is that member who must meet the test and not the whole VAT group collectively, that is, the nature of the third party supplies made by the VAT group member determine its eligibility not the aggregated third party supplies of the VAT group. Supplies within VAT groups are outside of the scope of VAT rather than being exempt or non-business supplies so cannot be treated as exempt or non-business by the VAT group member to determine whether or not it is eligible to join a CSG.