https://help.tallysolutions.com/docs/te9rel60/Tax_India/VAT/Tamil_Nadu/Sales_with_MRP.htm

Recording Sales at MRP (Tamil Nadu)

You can record a sales voucher such that VAT is calculated on the MRP.

To record sales transaction with tax on MRP

1.    Go to Gateway of Tally > Accounting Vouchers > F8: Sales.

2.    Select the customer name in the Party’s A/c Name field.

3.    Click F12: Configure.

4.    Select the required Sales Ledger.

5.    Select the stock item for which Calculate VAT on MRP is enabled and enter the Quantity, and Rate.

6.    Select the common VAT ledger. The rate will be calculated automatically based on MRP defined for the item.

7.    Enter Narration, if required.

The sales invoice appears as shown below:

8.    Press Enter to save.