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. Reference to the invoice number: Clearly state the invoice number and amount. Due date: Ensure the recipient knows when payment is due. In this article, we'll outline what you need to include to write a strong invoice email. Let's take a look at 18 email invoice templates for various situations and needs. You can customize as you see fit. Investigator Name: Address: City, State, ZIP: Phone: Email: Fax: Invoice Date: Case Name: Case Number: Invoice period: __________to ______.