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. You should be courteous and specific. Also, submit your invoices in a timely fashion. The Queen's Invoice Template. ▫ The Queen's Invoice Template is a legal business document. Discover how to craft effective invoice email templates that ensure quicker payments and keep clients uptodate with their account status. Below is a template for how to write an email with invoice attached separately.