Telephone numbers in the United Kingdom

Number format and dialing

Most UK numbers are dialled domestically with an initial 0 (the trunk prefix) and written with spaces for readability. For international use the leading 0 is omitted and the number is prefixed by +44 (for example +44 20 7xxx xxxx for a London number). Area codes and subscriber numbers vary in length, so common national lengths are ten or eleven digits including the trunk 0. The international E.164 form (+44...) is used for cross‑border routing.

Major categories

• Geographic numbers — usually begin with 01 or 02 and identify a town or region (London uses the 020 area code).
• Mobile numbers — begin with 07 and are used by mobile operators; numbers are generally portable between providers.
• Freephone — 0800 and 0808 are commonly free to call from landlines and, increasingly, from mobiles.
• National‑rate non‑geographic — 03 numbers charge the same as geographic calls and are used by charities, public bodies and businesses.
• Service and business numbers — ranges such as 084 and 087 have specific charging arrangements; callers should check charges before calling.
• Premium‑rate — 09 numbers are used for paid services and attract higher tariffs.
• Short codes and emergency services — three‑digit numbers such as 999 and 112 for emergencies and 111 for non‑urgent health advice.

History and regulation

Numbering in the UK moved from many local exchanges to Subscriber Trunk Dialling and later national planning to support growth and new services. A major renumbering in the 1990s (commonly known as PhONEday) reorganised ranges to increase capacity. The communications regulator oversees allocation, number portability and public information on charging; the current regulator publishes the national numbering plan and assigns blocks to operators.

Calling practices, billing and portability

Call cost depends on the prefix and the caller's provider. Regulations require providers to make call charges clear and to allow customers to keep numbers when switching operators in most ranges. Presentation of caller identity can be withheld by the caller, and voicemail, call barring and diversion services are widely available.

Practical considerations and future developments

When giving a UK number for international use, supply it in E.164 form with +44 and without the leading 0. Services such as VoIP and mobile data continue to change demand for numbering resources, and the plan is periodically updated to introduce new ranges or change rules. Consumers are advised to check their provider's charging information for non‑geographic and premium numbers before calling.