Adding custom internal notes to an invoice.
I am trying to add additional notes to an invoice after I have received payment. For instance: Check number, last four of the Credit card used, etc. I do not want to save this and have it sent to the customer. I have tried to just "Save" after I have typed in what I want saved and it will not save it. How can I save my necessary info without saving and sending it to the customer?
(Title has been edited by moderator for clarity)