An email invoice should include key details such as the sender’s name, contact information, company information, itemizations of goods or services provided, total cost, and payment due date. A clear description of how to pay the invoice should also be included. To facilitate easier processing, include an invoice number for the product/service offered, and consider using invoicing software or accounting software. In order to ensure timely payment, an informative yet polite tone should be maintained in the email body.