If you want to give your customer a discount, you can do this directly from the application. On the one hand, there is no need to calculate the discount by hand; on the other hand, you can better highlight a promotional discount on the invoice.
All you have to do is to check the ‘Discounts’ box, which is under the invoices fields:
– then write down the discount (loyalty discount, for example)
– and write the percentage that is reduced from the total invoice amount