How To Write A Gentle Reminder Letter For Payment . Dear sarah johnson, this is a payment reminder letter to formally inform you that your payment of [$167.44] is now past due. This client is on the verge of being problematic. 50 Polite Reminder Email Samples & Templates ᐅ TemplateLab from templatelab.com This client is on the verge of being problematic. For instance, if the customer is one week late with the payment, regpack can automatically send a prepared email. Dear (receivers name) this is a letter to notify you that the payment you owe, of (amount of money) was due on (date).