States' largest source of tax revenue: Identify the head through which Indian states earn the maximum revenue. Context: Consider the states' own tax revenue heads in a standard public finance framework. Choose the most appropriate revenue head.

Given data

• Focus: States' own tax revenue heads.
• Task: Identify the largest contributor in the conventional framework.

Concept / Approach
Historically, sales tax / VAT was the single largest state-level tax head. After 2017, State GST (SGST) took over that role in the GST framework; the economic essence remains the same: tax on sales/consumption within the state.

Option analysis
Sales tax / VAT (now SGST): Dominant own-tax revenue source for most states. Stamp duty: Important but smaller than sales tax/SGST in most states. State excise (alcohol): Significant for several states but typically below sales tax/SGST. Motor vehicle tax: Smaller share compared to the above.

Final Answer
Sales tax / VAT historically (now State GST share).