In most cases, overpayments must be paid back even if you have already spent the money and in some cases, a penalty may be applied. The salary overpayment resulted because .Make sure to fill out Annex B in your overpayment letter within the deadline provided even if you file a grievance. On Question 2, check the first box. Also write on the form: "I want all overpayments on my record to be waived, even the amounts you have already collected." Members receiving overpayment letters must respond promptly, as they are given four weeks to do so.