Inter-state service taxation between distinct persons: choice of invoice or ISD determines input tax credit distribution and valuation. Where a head office procures common input services from a third party attributable to both head and branch offices, the head office may either distribute ITC via the ISD mechanism (subject to mandatory ISD registration and attribution to the recipient) or issue tax invoices to branch offices so they may claim ITC. For internally generated services, if the recipient is eligible for full ITC the invoice value declared by the supplier is deemed to be the open market value regardless of whether specific cost components like employee salary are included; omission of salary cost is not fatal, and where full ITC exists a nil invoice may be deemed open market value. If full ITC is not available to the recipient, inclusion of HO employee salary cost in taxable value is not mandatory.