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.
A professional header: The first item on your freelance invoice should be your business name, or your full name, in professional (and easy to read) font. The font size should be a little bigger than the rest of the text on the invoice, and possibly even bolded for emphasis. Next you'll want to include your contact information: your mailing address, phone number, email address, website, etc., right underneath your business name.