You can give lumpsum discount in Rs. or Percentage. It’ll update that percentage in all items. NOTE: This lumpsum discount will not applicable on Locked Discount items.
Lock GST in Sales bill.
If you lock GST in Sales settings, you can’t edit GST% at time of creating Sales Bill
Go to Profile > Settings > Sales.
Lock Item Discount in Sales to avoid hassle.
If you set discount in item and lock that discount, You can’t not override item discount in Sale Bill. You can Lock Discount from Inventory Listing Page, Item Details Page & Save Set Location Page too.