The Regulations deal with the prevention and restriction of calling or CLI, for both incoming and outgoing calls.

The Regulations cover ‘call return’ and ‘call display’ facilities, such as the display on certain telephone equipment that alerts the subscriber to the identity of the caller before the connection is made, and the 1471 service. CLI services are governed by an Ofcom-published code (the Code of Practice for Network Operators in relation to Customer Line Identification Display Services and Other Related Services). Following the Code will help ensure compliance with the Regulations.

Outgoing calls

The communications service provider must ensure that:

  • a user originating a call, has a simple way of preventing the identity of the calling line for that call appearing on the connected line;
  • a subscriber has, in relation to their line and all calls originating from that line, a simple way of preventing the identity of their line appearing on any connected line.


You should note the distinction between the user and the subscriber: User only have the right to block their identity in relation to a particular call, whereas subscribers have the right to block their identity in relation to their line and all calls originating from that line. In either case, users or subscribers must not be charged for this facility.

Incoming calls – preserving the anonymity of the caller

For incoming calls, the communications service provider must ensure the called subscriber has a simple way of preventing the identity of a calling line appearing on the connected line. There must be no charge for reasonable use of the facility.

This is particularly likely to be used where the caller’s anonymity is guaranteed, such as on helplines like the Samaritans, Alcoholics Anonymous or police information lines.

Incoming calls – preserving the anonymity of the called line

Under the Regulations, the relevant telecommunications service provider must ensure the subscriber to whose line a call is forwarded has a simple way of preventing, without charge, the identity of the connected line appearing on any calling line.

This facility preserves the privacy of someone to whose line a call is forwarded, where the connected line has a different number from the number called. This is a facility used by many businesses and medical practices; for example, a call to a doctor’s surgery after hours may be forwarded to the number of a doctor or locum service. This facility will enable the number of the line to which the call is forwarded to remain private.

Anonymous incoming calls – call rejection

If a caller has prevented the identity of the calling line appearing on the connected line, the called subscriber must be given a simple way of rejecting those calls. The Regulations do not mention charging for this facility.

The current technical standards do not distinguish between a situation where CLI has been deliberately withheld and where CLI is unavailable, for example, for incoming international calls. So a subscriber who chooses not to receive calls with CLI withheld may also not receive all international calls. If calls are rejected because the CLI has been withheld, the caller should receive an automatic message explaining why the call has not been connected and how to lift the block on CLI to enable the call to go through.

The Telecommunications (Data Protection and Privacy) Regulations 1999 obliged service providers to give called parties a simple way of rejecting a call where the CLI has been withheld. The Commissioner understood at that time that there were technical problems associated with offering a fully automatic call-rejection system to all subscribers. In the case of most mobile phone subscribers, the only way to reject a call made with CLI withheld was not to answer, or to press ‘line busy’. On some networks this resulted in the call being transferred to the subscriber’s voice mail.

The Privacy and Electronic Communications (EC Directive) Regulations 2003 contain a clearer requirement to provide automatic call rejection. The Commissioner’s current understanding, based on Ofcom’s advice, is that as the relevant Regulation applies to the automatic rejection of voice calls only, automatic call rejection can be implemented relatively simply by using a recorded voice message to explain what has happened.

Duty of an electronic communications service provider to advise that CLI is available

A communications service provider who offers CLI facilities must take all reasonable steps to publicise that they do so and to explain the consequences of the Regulations about CLI.

Malicious or nuisance calls

There are provisions to help trace malicious or nuisance calls where a subscriber has notified the relevant communications service provider that such calls on their line should be traced.

In these situations, the communications service or network provider, as appropriate, may override anything done to prevent the identity of the calling line appearing on the subscriber’s line, if the provider in question thinks it necessary to trace malicious or nuisance calls.

For these calls, the provider, as appropriate, may hold and make available to a person with a ‘legitimate interest’ in this information, data containing the identity of a calling subscriber. Sometimes the service or network provider may not be able to reveal the identity of the person making the call, but merely the location from which the calls were made. For example, it would be difficult for a telecommunications service provider to provide the identity of a caller using a number attached to an unregistered pre-paid mobile.

It is important to distinguish a person with a ‘legitimate interest’ under the Regulations, from the reference to ‘legitimate interests’ referred to in paragraph 6 of Schedule 2 of the Act. The Commissioner has given a wide interpretation to ‘legitimate interests’ under the Act. It relates to the ‘legitimate interests pursued by the data controller or by the third party ... to whom the data are disclosed’. In the Regulations ‘a person with a legitimate interest’ is not defined, but it probably includes the police or other law enforcement body and even the subscriber himself or herself.

However, there may be cases where a service provider would wish to exercise some caution with a request for information about the identity of a calling subscriber. For example, if the service provider is not satisfied that the calling subscriber has abused the service in the way referred to in Regulation 15, it may choose not to release that information to the called subscriber. However, it may not rule out releasing it to the police if any further request provides an extra level of reassurance.

Calls to emergency services

CLI cannot be excluded from all outgoing calls using the national emergency call number 999 or the single European emergency call number 112. This is to enable the emergency services to deal with such calls and easily identify the caller’s location.

The restriction on processing of location data under Regulation 14(2) shall be disregarded.

Termination of unwanted automatic call forwarding

If calls are being forwarded as outlined in incoming calls – preserving the anonymity of the called line, the subscriber has the right to ask the relevant communications service provider to stop that service without unavoidable delay. Any other network or service provider must also comply with all reasonable requests for this.


Some of the Regulations require a facility to be provided free of charge. Where the Regulations do not mention that a charge may be made for a service, then if a person must provide a facility, or ensure it is provided, they can ask for a reasonable charge unless there is an indication to the contrary.