. How to configure taxes, discounts etc in sales transactions?

The Tax applied on the Sales invoice in BUSY depends on the sale type that you choose while entering the voucher. For example, if you select I/GST-12% as the sale type, the invoice will have 12% GST for inter-state transactions. Similarly, if you select L/GST-18% as the sale type, the invoice will have 18% GST for intra-state transactions and so on. You can choose from different sale types according to your business needs and GST rules. 
Furthermore if you choose Item-wise, Multirate & Tax inclusive as the sale type, the GST rate will be taken from the item masters. This means that you can have different GST rates for different items in the same invoice.
BUSY offers two methods to apply discounts to your invoices. These are:
Item-wise Discount: This method allows you to apply a discount percentage or amount for each item in the invoice. You can use this method if you want to give different discounts for different items. To enable it follow these steps:
Step 1: Go to Administration and click on configuration.
Step 2: Choose the Voucher Series Configuration option and select the voucher type that you want to apply the discount for, such as sale, purchase, etc. Then, select the voucher series and click on Voucher Configuration.
Step 3: You will see the "Item-wise Discount feature". Set it to Y to enable it and choose the discount structure from the drop-down list. Then, click on Save.
Step 4: Now, when you create an invoice, you can enter the discount percentage or amount for each item after entering the item details.
Bill-wise Discount: This method allows you to apply a discount percentage or amount for the whole invoice. You can use this method if you want to give a uniform discount for the entire bill. For apply this you can use the Bill Sundry option in the voucher. There is a bill sundry already created with the name Discount You can select this option and enter the percentage or amount of the Discount. This will deduct the Discount from your invoice.