What should your invoice include? - 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.
Keep in mind whether your industry is one where you invoice upfront before any work has been completed. In this case you'll be detailing the progress of the project as opposed to doing a monthly invoice.