Each thermostat has a unique MAC ID and MAC CRC which is unique to your device. You’ll need to know these numbers in order to register your thermostat or to perform some troubleshooting activities. The MAC ID and MAC CRC represent the alphanumeric code displayed on the thermostat screen during the registration process. It is also located on the thermostat registration card inside the thermostat packaging. You can also find it on the back of the thermostat simply by taking the thermostat off the wall plate.
For more information, please watch this instructional video: