Select the line item that you would like to apply a discount
In the Discount field enter the amount of the discount
Select the currency symbol button if the discount is in currency or the percentage % button if the discount is a percentage
Tap the Accept button to apply.
Tap the plus icon (+) located at the left side of the Discount line in the subtotal section. A discount box will appear.
Enter the discount amount or percentage that will be applied to the sales document
Set the Tax Before Discount option depending on your local tax laws. Enable this option to calculate the tax before any discount is applied. Disable it to calculate the tax after the discount is applied.