However, you can also specify percentages manually when editing an invoice line item. To do this simply put a percentage into the price column when editing the invoice. You can either enter a positive amount, e.g. 12% to add 12% or enter a negative amount, e.g. -12% to deduct from the invoice.
Note that when entering a percentage as a line item, the percentage always applies to the previous item on the invoice. If you want the percentage to apply to ALL previous items on the invoice, enter a subtotal first then enter a new line item below the subtotal to include your percentage value.
For more help, see: