United Kingdom voice guidelines
Voice calling guidelines for United Kingdom (GB), covering reachability, caller ID formats, DTMF support, and emergency services.
Locale overview
| Field | Value |
|---|---|
| Country | United Kingdom |
| ISO code | GB |
| Region | Europe |
| Dialing code | +44 |
Reachability
United Kingdom supports inbound and outbound calls for domestic, international, and toll-free number types.
| Call type | Inbound | Outbound |
|---|---|---|
| Domestic | Supported | Supported |
| International | Supported | Supported |
| Toll-free | Supported | Supported |
Outbound caller ID restriction
Starting May 15, 2023, Ofcom regulations require that outbound caller IDs be valid and uniquely identify the caller, or contain a dialable telephone number. Outbound calls using invalid or non-compliant caller IDs will be blocked by the carrier network.
Caller ID
| Call type | Direction | Format |
|---|---|---|
| Domestic | Inbound | +E.164 |
| Domestic | Outbound | Local format |
| International | Inbound | E.164 (non-guaranteed) |
| International | Outbound | +E.164 |
| Toll-free | Inbound | +E.164 |
| Toll-free | Outbound | Local format |
DTMF support
RFC 2833 DTMF format is supported for both inbound and outbound calls in the United Kingdom.
Emergency services
Calls to emergency services numbers in the United Kingdom are supported.
Compliance note
These guidelines summarize carrier requirements at the time of publication and do not constitute legal counsel. Verify that your implementation complies with all applicable telecommunications regulations in United Kingdom.