You can make any changes necessary for existing Invoices. To call the form for edit of Invoice click " Invoices" button on the main form. From the Invoices List form, you have to choose the Invoice and click on the "Edit" button( or double click on the Invoice row). You can change, add and remove Invoice information using any functions of the Invoice form . We don't recommend you to make any changes in the Invoice after it has been sent to your customer. You can prepare another Invoice for the required adjustment.