The Serial # and PIN can be found on the back of your ID plate. For the Wrist ID Elite and Wrist ID Slim, you can simply take the ID off your wrist and look at the inside of the plate. For the Shoe ID, however, a bit more work is necessary. The following link will show you some simple animations that will explain how the ID plates can be disengaged from the band/strap.http://www.myroadid.com/SerialPinHelp.aspx