State tax exemption on used vehicle supplies where tax applies only to the supplier's margin, subject to credit exclusions. Exempts state tax on intra-state supplies of specified old and used motor vehicles by taxing only the supplier's margin. Vehicle categories are defined by engine, fuel type and dimensions, with margin calculated as consideration minus depreciated value for depreciated goods or as selling price minus purchase price otherwise; negative margins are ignored. The exemption is inapplicable where the supplier has availed input tax credit, CENVAT, Bihar VAT credit or other tax credits on the goods, and the notification prescribes specified tax rates and effective commencement.