How To Write A Letter Reminding Payment . Hi john doe, this is just a reminder that payment on invoice #10237 (total $5,400), which we sent on march 25th, is due today. A reminder letter is important because without it, the bill may never get paid. 5+ Payment Reminder Letters Find Word Letters from www.findwordletters.com Name, address, and contacts of the recipient. [ their business name] invoice outstanding [ #reference number] hi, [ their name ] i hope you’re well. You can make payment to the bank account specified on the invoice.