Notes: Many people overlook it, but the notes section on the invoice can be invaluable. A simple phrase like "Thank you for your business" will leave a good impression to the customer and increase the chance of an invoice getting paid faster. You can also include Payment Instructions, Warranty Information or even a personalized message in this section to make them feel really special.
Discount: If you are offering a discount to your valued customer, include the number here. They will appreciate it and remember good things about doing business with you.