CSE1150 | Introduction: What is meant by ‘members’ of a CSG?
From HM Revenue & Customs · VAT Cost Sharing Exemption Manual
A member of a CSG is a business or organisation that:
is capable of jointly owning and controlling a CSG;
receives ‘qualifying supplies’ from the CSG
A cost share group A can be a member of another cost share group B, provided that B itself makes supplies to A that fall within the exemption groups in CSE1030.