Use a digital format – Using a digital format is one way to ensure your invoice is professional, and to indicate that you're likely to use the latest tools, and follow best practices, on the job. Simple mobile apps like Invoice2go will allow you to create and send professional estimates and invoices on site when the project is still fresh in your client's mind. These apps can even store receipts so you have a real-time way to keep your expenses organized for easy presentation to your clients.
Accurate billing is extremely important when it comes to independent contractors and small business owners. You can't afford to lose a customer over something that should be done right the first time. Business owners who provide detailed, prompt invoices straight to the customer's inbox come out way ahead in the credibility stakes.