Ambiguous: "Please settle the outstanding balance as soon as possible. Writing and sending the letter provides proof that you have notified the other person of this Outstanding Debt and have Requested Payment.Follow these 10 tips to write overdue payment letters for requesting outstanding payments from your late paying customers. Recovering overdue funds from customers is frustrating. These overdue invoice letter templates show you the right tone and language to use. Do You Owe Taxes on Settled Debt? Recovering overdue funds from customers is frustrating. These overdue invoice letter templates show you the right tone and language to use. In some cases, you may also have to pay taxes on the debt that is canceled out in your settlement. "Deferred Payment Notice.