- Anonymous call rejection turns away incoming calls where the caller has withheld their Calling Line Identification (CLI), a presentation control defined in Ofcom's CLI guidelines.
- On many BT-based lines the feature is enabled by dialling 1227 and disabled by dialling 1228, though codes vary by provider.
- Rejected callers typically hear a recorded announcement explaining the call has not been connected and inviting them to redial with their number shown.
- The feature relies on the network passing CLI, so it cannot judge whether a withheld call was a wanted contact or a nuisance caller.
- Ofcom's General Conditions require communications providers to offer CLI facilities and to allow callers to withhold their number, which is why some legitimate callers appear as anonymous.
Anonymous call rejection blocks incoming calls from numbers that have been withheld. On BT lines it is usually switched on by dialling 1227 and off by dialling 1228, and rejected callers hear a recorded message.
Last reviewed: June 2026
What anonymous call rejection actually does
Every standard landline call carries a piece of signalling information known as the Calling Line Identification, or CLI. This is the data that tells the receiving exchange, and ultimately the handset display, which number is calling. Anonymous call rejection is a network feature that inspects this signalling before the phone rings. If the caller has chosen to withhold their CLI, the network refuses to connect the call and the handset stays silent.
The important distinction is that the feature does not block specific numbers it dislikes. It blocks the absence of a number. A caller who has dialled the prefix to withhold their CLI, or whose line is configured to present no number, will be turned away regardless of who they are. A caller whose number is presented normally will get through, even if that number belongs to a nuisance operation. The feature is therefore a blunt instrument aimed squarely at the category of callers who deliberately hide their identity.
Ofcom's General Conditions of Entitlement require communications providers to make CLI facilities available and to allow callers the option to withhold their number. That regulatory balance is the reason anonymous calls exist at all: withholding a number is a legitimate privacy choice, used by businesses, helplines and individuals alike. Anonymous call rejection simply lets the receiving customer decline calls that exercise that choice.
How to switch anonymous call rejection on and off
On the most common BT-based network arrangement, the feature is controlled with short dialling codes from the handset. Dialling 1227 enables anonymous call rejection, and dialling 1228 disables it again. After dialling, the line usually plays a confirmation announcement stating that the feature has been turned on or off. No additional equipment is required, because the screening happens inside the network rather than in the phone itself.
These codes are not universal. Providers that run their own platforms, or that resell access over Openreach lines, may use different short codes or may require the feature to be activated through an online account or by contacting customer service. Anyone unsure of the correct code should check the provider's published feature guide rather than assume the BT codes apply. VoIP services in particular often expose the setting as an on-screen toggle instead of a dialled code.
Because the control is per-line, switching the feature on affects every handset connected to that line. There is no way to apply it to one extension and not another using the dialled codes alone. Households that share a line should agree before enabling it, since any wanted caller who routinely withholds their number will be turned away for everyone.
Anonymous call rejection setup and limitations
The table below summarises how the feature is typically set up and where its limits lie. Exact codes and charges depend on the provider, so treat the BT codes as the common default rather than a guarantee.
| Aspect | Typical behaviour | Limitation |
|---|---|---|
| Enable code | Dial 1227 on BT lines | Codes differ on other providers and VoIP |
| Disable code | Dial 1228 on BT lines | Setting applies to the whole line |
| What it blocks | Calls with withheld CLI | Cannot block calls that show a number |
| Rejected caller experience | Hears a recorded announcement | Wanted withheld callers also turned away |
| Cost | Free or bundled on many tariffs | Some providers charge a monthly fee |
Whether anonymous call rejection is free
The cost picture is not uniform. Several providers include anonymous call rejection as a standard part of the package at no extra charge, while others treat it as a chargeable add-on or bundle it within a wider calling-features pack that carries a monthly fee. Because Ofcom does not set a fixed price for the feature, the only reliable way to know is to read the provider's published price list or call-features page.
Where a charge does apply, it is generally a small recurring amount rather than a per-use cost, since the screening happens automatically once the feature is switched on. There is normally no charge for dialling the enable or disable codes themselves. Anyone reviewing their bill who finds an unexpected line item for call features can usually identify it from the provider's tariff documentation.
What happens to the calls that get rejected
When a withheld call is rejected, it never reaches the handset, so there is no missed-call record on the phone and no ringing. Instead, the caller hears a recorded announcement on the network. The exact wording varies, but it generally explains that the person being called is not accepting withheld numbers and suggests the caller redial showing their number. A caller who wants to get through can usually do so by dialling the prefix that presents their CLI, commonly 1470 on BT lines, before the destination number.
Because rejected calls are stopped inside the network, the receiving customer has no log of who tried to call. This is the trade-off at the heart of the feature: it removes the nuisance of withheld calls entirely, but it also removes any chance of seeing that a withheld call was attempted. For most households the silence is the point, but anyone expecting an important call from a withheld number, such as certain medical or official lines, should weigh that before switching it on.
Anonymous call rejection alongside other protections
Anonymous call rejection is most effective when treated as one layer among several. It cleanly removes withheld calls, but it does nothing about the large volume of nuisance traffic that presents a visible number, including spoofed numbers that display a fake but valid-looking CLI. For that reason many households combine it with network-level screening services and with last-number recall to identify callers who do present a number.
It is also worth remembering that the all-IP migration is changing how these features are delivered. As the traditional PSTN is retired and the network completes its move to all-IP by 2027, calling features that were once exchange functions are increasingly handled by the broadband router or the provider's VoIP platform. The feature itself persists, but the method of switching it on may shift from a dialled code to an account setting.
Frequently Asked Questions
What is anonymous call rejection?
It is a network feature that turns away incoming landline calls whose caller has withheld their number. The phone does not ring, and the caller hears a recorded message. It blocks the absence of a presented number rather than any specific phone number.
How do I turn on anonymous call rejection?
On many BT-based lines you switch it on by dialling 1227 and off by dialling 1228, with a confirmation announcement after each. Other providers and VoIP services may use different codes or an online account toggle, so check the provider's feature guide if the BT codes do not work.
Is anonymous call rejection free?
It depends on the provider. Some include it at no extra cost, while others charge a monthly fee or bundle it within a calling-features pack. There is no Ofcom-set price, so the provider's published tariff is the only reliable guide.
What happens to calls I reject as anonymous?
The call never reaches your handset, so there is no ring and no missed-call record. The caller hears a recorded announcement explaining the call was not connected and is usually invited to redial showing their number, often by dialling 1470 first on BT lines.
Does anonymous call rejection work on VoIP?
Many VoIP services offer an equivalent, but it is usually controlled through an app or online account rather than a dialled code. As the network completes its all-IP migration by 2027, withheld-call screening is increasingly delivered by the provider's platform, so the exact method varies between services.
