Here's a standard format you can follow: 1> Subject Line: Make it clear and concise. Want to know how to write an email with an invoice attached?Read on for our top tips, as well as a sample invoice email you can use for your customers. You'll learn essential tips to write the best invoice emails and provide 6 invoice business email templates and a template for you to use. Use this invoice email template to write and send invoices that are straightforward and easy to understand, making it easier for you to get paid on time. Easily create and send professional invoices with our free customizable template and samples. Get paid faster and streamline your billing process. We have created two invoice message templates for various situations so that you can fill in the essential details, upload a file, and send your message. Invoice emails should be clear, concise, and easy for the client to understand. Here are seven ways to ask for your payment while keeping communication professional.