You can record purchase of exempt works contract by selecting the nature of transaction Purchase Exempt - Works Contract.
This nature of transaction is provided for West Bengal.
To record an invoice for exempt works contract
1. Go to Gateway of Tally > Accounting Vouchers > F9: Purchase.
2. Enter the Supplier invoice no. and Date.
3. Select the party ledger in the field Party's A/c Name.
4. Select the purchase ledger grouped under Purchase Accounts with the Nature of transaction set to Purchase Exempt - Works Contract.
5. Select the stock item. Enter the amount. The purchase invoice appears as shown below:
6. Press Enter to save.
The value of this transaction gets captured in the relevant fields of state-specific VAT/CST forms and annexures.