Dear …

Just a friendly reminder to you that your account with __(Name of Organization)__ is currently overdue. Please refer to invoice __(#(s)__, dated __(date(s)__. Feel free to contact us if you have any questions about__(this/these)__ invoice(s). We’d be happy to discuss the details with you. If you’ve already sent in your payment, please accept our thanks and disregard this notice. We appreciate your continued business and look forward to hearing from you soon.

Sincerely,