Subject: Quick reminder about invoice Invoice number
Hi Who you are writing to,
I hope all is well. This is a quick reminder that invoice Invoice number for Amount due was due on Due date, and I have not received payment yet.
If you have already paid, thank you, and please ignore this message. If not, you can pay by:
How to pay you
I have attached the invoice again in case it is useful. Could you let me know when I can expect payment? If there is a problem with the invoice, just reply and I will sort it out.
Many thanks,
Your name