To apply a credit to a partially paid invoice, click on the invoice and then click ‘Credit memo.’
OR, you may click on the ellipsis menu and click ‘Credit memo.’
There you will be able to add a credit memo up to the outstanding balance of the invoice. You may enter any optional internal notes or files. Then click ‘Apply credit memo.’
When creating an invoice, you have the option to apply a discount, either as a monetary number or percentage. You may also edit an invoice against which no payment has processed.