This notice is sent by a service provider to its customer in case payment is not yet made for the service provided despite having the bill sent.
It is needed if you as a service or goods provider have rendered service or goods and the payment is still due from the customer's side.
To make it legally binding, the notice must be sent by the service provider to the customer through a lawyer. The notice must be duly signed by the lawyer on his/her letterhead.
You as a goods or service provider may use it if you have delivered service to a customer and the payment is still due despite having the bill sent already. In such cases, this notice can be used.