For some items like cigarette/tobacco, government has added additional cess on per unit basis. To add additional cess in Book Keeper, follow these steps:
1. You need to first create CESS account and Tax Group for GST@40% and IGST@40% or whatever tax group you need. Check out this video, how to create CESS account and Tax Group: https://www.youtube.com/watch?v=ks45b6jrjEg
2. Create new item, select default tax account and add additional CESS.
3. Create new invoice on PER ITEM mode, add item and apply tax. Please note that additional cess won't be computed in ON TOTAL mode.
4. Book Keeper will automatically calculate proper CESS and will display in invoice as well as in HSN Summary.
5. This is also reflected in GSTR3B and GSTR1 reports