Final answer:
The store can use a payment notification tool or reminder system to tell when a customer's payment is due. They can also utilize a due date alert service and maintain a customer payment schedule to keep track of due dates and send reminders to customers.
Step-by-step explanation:
The store can tell when a customer's payment is due by utilizing a payment notification tool or reminder system. These tools are designed to send automated reminders to customers regarding their pending payments. One such example is a Payment Reminder System which sends notifications to customers when their payment is due.
In addition to this, stores can also use a Due Date Alert Service to inform customers about their upcoming payment due dates. This service helps customers stay on top of their payment obligations and avoid late fees.
Furthermore, a store can also maintain a Customer Payment Schedule to keep track of when customers' payments are due. By having a systematic record of due dates, the store can proactively follow up with customers who have missed their payments.