Dell XPS 18 (1820, Early 2014) - Manual (Page 39)

Troubleshooting │ 39
Locating Your Service Tag and Express
Service Code
You need your computer’s Service Tag/Express Service Code when
you contact Dell for technical support or other queries. The Express
Service Code helps the automated telephone support system redirect
your call to the appropriate support department.
The Service Tag and Express Service Code for your computer are
located on a label at the back of your computer.
CAUTION: Lay your computer face-down on a soft, clean
surface down before you look for the Service Tag and
Express Service Code.