The best thing about using an invoice system is that you can track your time against the amount you're getting paid for each task. In order to run a successful business, you want your hourly rate to be profitable so you're not losing time and money. Another benefit of using an invoicing system is that you'll never save over an invoice and lose the work you've calculated for another client.
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.