Percentage Discounts are for variable amounts you want to reduce the order by. You would use a Percentage Discount to reduce the invoice total by 10%, for instance.
Create Percentage Discounts just like you would Percentage Fees but use a negative number in the "Rental Price" field. In our example, for 10% off, you'd enter "-10."
On Orders, Percentage Discounts will calculate based on everything above them in the list of Line Items.
Keep in mind that any Percentage Discounts will modify the Adjusted Line Item Prices of your other Line Items.
You can change the unit price of any of these Percentage Discount as you need to on a particular invoice.
Also see: Percentage Fees & Discounts