To enable this option
1. Go to Gateway of Tally > F11: Features > Statutory & Taxation.
2. Set the option Enable Value Added Tax (VAT)? to Yes.
3. Set the option Enable VAT on quantity to Yes, in the Company VAT Details screen, as shown below:
To configure stock item for VAT on quantity calculation
1. Go to Gateway of Tally > Inventory Info. > Stock Items > Create or Alter.
2. Specify the required details in fields Name, Under, and Units.
3. Set the option VAT Applicable to Applicable.
4. Enable the option Set/alter VAT details? to open VAT Details screen.
o Specify the Classification, Type of Goods, Commodity Name, Commodity Code, Tax rate, and Tax type.
o Set the Calculation Type as On Quantity.
o Specify the Tax rate of the item per quantity.
o Press Ctrl+A to accept the VAT Details screen.
5. Press Ctrl+A to accept the Stock Item Creation screen.