Ofcom Statement: Guidelines for Calling Line Identification Facilities

Telecoms /

Guidelines for Calling Line Identification Facilities

On the 26th April 2018 OFCOM published a statement in relation to the guidelines for Calling Line Identification facilities

What is Caller Line Identification (CLI)?

Caller Line Identification (CLI) data consists of a number that identifies the caller and a privacy marking, which indicates whether the number can be shared with the recipient of the call.

Simply put it means you will see the callers number on your phone display when they call.

What can it be used for?

CLI can give the recipient of a call information about the party making that call.

CLI Data can also be used for other functions, such as call tracing to identify the sources of nuisance calls or as a reference to help identify the location of a caller in emergency situations.

For this to work effectively, the CLI Data must be accurate.

What we must provide?

In Autumn 2017 Ofcom introduced a new regulation which required communications providers to provide CLI facilities and ensure that the CLI data provided with a call includes a valid, dial-able telephone number which uniquely identifies the caller.


Ofcom updated the guidelines and clarified the definition of a valid and dial-able CLI for communications providers in different parts of a telephone call, based on what is possible today.

We are responsible for ensuring accurate CLI data is provided with a call.

Transit and terminating providers are expected to check that the number provided with a call is from a valid number range.

For calls that originate on a network outside the scope of these requirements, the CP at the first point of ingress is responsible for ensuring that the call is populated with valid CLI Data, replacing the information with a number that has been allocated to them for this purpose where the original number is not valid or is missing.

The updated guidance also clarifies the options available to CPs to prevent calls with invalid or non-dial-able CLI from being connected to the end user.

The revised guidance will apply from 1 October 2018, the same date that the new General Conditions come into effect.

The full report and guidelines can be downloaded here:


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