Best practice in my opinion is to void the overpaid paycheck and reissue corrected amount in your payroll system. My former employer, the NYC Department of Education, kept paying me for three and a half months after I tendered my resignation.If you were paid money that is not rightfully yours (an overpayment), it doesn't matter that it occured after the employment relationship ended. If you pay an employee more than they should have received in a pay period, you need to know how to correct a payroll overpayment. For social security and medicare tax, you need to file a separate form 843. The Overpayment Worksheet provides the Payroll Office with the information needed to process the overpayment and recover the overpaid funds. It's a Form 941 for reporting payroll taxes.