Invoice: This indicates the purpose of the commercial document and should be placed near the top of the page. Name of your business: Format in bold and place at the top of the page. Include your company logo for a branded look. Seller contact information: This not only lets your customer know how to contact you if they have any questions about the invoice, but could also lead to future business; if they are happy with their experience working with you, they might use the information to contact you again or refer you to a friend.
When you work out the contract with each client (and yes, you should have a contract in place!), you'll list out the terms of how often you plan to invoice and when you should be paid. For instance, you can agree to bill on the first of each month, or biweekly so you get paid every other Friday. 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.