I'm concerned because my check payment to the IRS has not been cashed
                        yet. What should I do?
                     
You can call (800) 829-1040 and ask an IRS representative if the payment
                        has been credited to your account. If it has not and the check has not cleared
                        your financial institution, you may choose to place a stop-payment on the
                        original check and send another payment.