The serial number of your tado° devices can be found:
In the app:
Go to Settings > Rooms & Devices. The serial number appears just below the device name on the list. If one room has multiple Smart Radiator Thermostats, tap on Blink Display and the corresponding Smart Radiator Thermostat’s display will flash 'Hi' helping you identify the device.
On the side, back or under the cover of the device as shown.
You can also find other registration information like auth code and QR code here.
Wireless Temperature Sensor
Smart Radiator Thermostat
The Wireless Receiver - Programmer with Hot Water Control (UK)
The Wireless Receiver (EU)
Smart AC Control
Storing registration information on the Setup Guide
Every tado° device comes with
a removable sticker containing the registration information, and
a Setup Guide.
Paste this sticker onto the Setup Guide to keep your registration information handy.