https://www.gov.uk/government/publications/corporation-tax-group-and-consortium-ct600c-2006-version-2
Corporation Tax: group and consortium (CT600C (2006) Version 2) - GOV.UK
Use supplementary pages CT600C (2006) Version 2 if you are claiming or surrendering relief under group or consortium or unrelieved foreign tax provisions.
corporation taxgroupconsortium