A review of definitions provided in respective State VAT Acts will make it clear that those statutes will be applicable to the respective States. The statutes will provide that the provisions are extended to whole of state of ........
Imagine a situation where tax rate is beneficial in one state compare to other States. Here to take benefit of tax, the dealers may register in the State in which the rates are beneficial and deal in goods in other States!!!!! The effect will be that the state in which the goods are purchased are sold will be deprived of tax revenue....
When the resources in the form of men, infrastructure (roads etc.,) are being made use in the state in which the transactions are effected, the relevant revenue should also be earned by the State in which purchase & sale takes place....
In Case of Central levy like Income Tax, the authority will have the jurisdiction to assess the person across the Country. In case of State levy like VAT, the boundaries within the State will be the jurisdiction. So transactions effected beyond the jurisdiction (of Delhi in this case) can not be subjected to tax. Similarily, just coz the dealer is not registered, the levy can not be made ineffective in the state in purchases & sales are being made (Kolkata).