These days, the telephone number of the caller travels ahead of most calls. This is known as Calling Line Identity (CLI) or by BT as Caller ID.
You will probably most often see this when someone calls your mobile phone. This is also known in the USA as Automatic Number Identification or ANI.
This number can be used by CTI software to match up to a computer record for that caller.
Author: Robyn Coppell
Reviewed by: Megan Jones
Published On: 2nd Feb 2023 - Last modified: 25th Sep 2025
Read more about - Definitions, Terminology
