The Notice of Past Due Payment is simply a communication to another person or business informing them that they have failed to meet their obligation to make a payment and that it is now past due. This is usually done by way of sending two notices. The first one is a gentle reminder that the payment is past due and is probably more appropriate as a first notice. The second notice has a somewhat more confrontational tone and basically communicates that other, more serious recourse is available to the debtor and will be taken if payment isn’t made.
Definition of Notice of Past Due Payment.
You can find various examples of Notices of Past Due Payment here.