The salary overpayment resulted because . Notify Employee: The Agency must immediately notify the employee, in writing, of the amount overpaid and the method of recovery.In the event I leave employment with this agency, I authorize the overpayment balance to be deducted from my final payroll payment or terminal leave cashout. OPM explained its decision in a letter to Mr. Harris dated August 11, 2005. You're correct, forgiveness for payments over 120 are automatically refunded.