I have a very difficult time telling a new client that I am all scheduled and completely filled up to a response to an inquiry for income tax prep to something like. Thank you for contacting me regarding your income tax preparation needs.  I would be happy to take care of your tax filing needs but I am totally booked from now until April 18.  If you would like me to e-file the extension for you please let me know and we can then meet later in April or early May... something like that. anyway.. tried it for the first time and they wrote back, sure.