As the payment is now overdue, we kindly request your immediate attention to settle the outstanding balance. Need to write a strong Demand Letter for payment Oakland?Below, we've created an example of a debt settlement proposal letter that you can use as a guide. Your letter can be sent via your preferred contact method. Follow these 10 tips to write overdue payment letters for requesting outstanding payments from your late paying customers. Mention the invoice number, date, and amount due. 6 demand letter templates to recover unpaid invoices. We've created ready-to-use collection letter templates. Read on below to find out what every letter should say in order to collect payment as soon as possible. Recovering overdue funds from customers is frustrating.