Exemption of State tax on specified used vehicle supplies limited to the supplier's margin and subject to credit restrictions. Exemption reduces State tax on intra state supplies of specified old and used motor vehicles to the extent the tax in Notification No.1/2017 exceeds the notified rates, applying only to the supplier's margin. Margin for depreciated assets is consideration less depreciated value; otherwise it is selling price less purchase price; negative margins are ignored. Exemption is inapplicable if input tax credit, CENVAT or VAT credit has been availed.