You can attach files—such as a detailed time report, design drafts, or additional project information—to an invoice before sending it to your client. You can also attach an Expense Report, which will contain receipt images entered with your expenses.
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.