Inter-office service taxability: head office may use ISD or invoice branches to enable input tax credit claims. Head office and branch office inter office service supplies: head office may either distribute input tax credit via the Input Service Distributor mechanism (registration required if used) or issue tax invoices to branches for third party input services attributable to them; distribution or invoicing is allowed only if services are attributable to or actually provided to the branch. For internally generated services, invoice value is deemed open market value where recipient is eligible for full ITC irrespective of included cost components; salary cost need not be mandatorily included where recipient is not eligible for full ITC.