2) MAKE A COPY OF EACH CERTIFIED MAIL RECEIPT which you received back indicating. How do I pay back my overpayment?Overpayments happen for various reasons. For example, DES may not budget your correct income or resources. If you have questions regarding paying your bill, payment plans, payment options, or anything else related to your Pima student account, we're here to help. The salary overpayment resulted because . Notice Regarding Appeal Rights.