This error is displayed when the nature of adjustment is not selected in the voucher.
To resolve the exception Unable to determine Nature of adjustment
1. Go to Gateway of Tally > Display > Statutory Reports > Service Tax Reports.
2. Click the category Unable to determine Nature of Adjustment.
3. Select a voucher that does not have nature of adjustment defined.
4. Click S: Set nature of Adj.
5. Select the required Nature of Adjustment, as shown below:
6. Press Ctrl+A to accept.