Inter-office service taxation: invoice value deemed open market value when recipient is eligible for full input tax credit. The circular clarifies that a Head Office may either distribute ITC for common input services through the ISD mechanism (requiring ISD registration) or issue tax invoices to Branch Offices so BOs can claim ITC; ISD distribution is optional and limited to services attributable to or actually provided to BOs. For internally generated services, where the recipient BO is eligible for full ITC the invoice value is deemed the open market value regardless of inclusion of cost components; absence of an invoice may result in a deemed nil declared value treated as open market value. Salary cost need not be mandatorily included when BOs lack full ITC eligibility.