Geographic telephone numbers in the UK always have nine or ten digits after the 0 trunk code or +44 international dialling prefix.

The Big Number Change removed many, especially in Northern Ireland, and by July 2005 there were only 329 ranges in 42 codes.

Three-digit area codes are generally used for the UK's largest cities and conurbations (with the obvious exception of London) and always have seven-digit subscriber numbers and always begin 011x or 01x1.

This is the geographic number format for the first round of five large cities moved to all figure dialling in the 1960s, and subsequently also used in the metropolitan county of Tyne and Wear, eastern County Durham and south-eastern Northumberland from the 1980s onwards.

This is the geographic number format for the second round of large cities and towns moved to brand-new three-digit area codes.

The former Reading area code had already been changed once, by adding a "1" directly after the initial zero as a part of PhONEday in 1995.

The first four digits of the local number identifies a small area within the town, city or region.

All of these areas were also subject to a previous code change, one that added a "1" directly after the initial zero as a part of PhONEday in 1995.

[11] Recently, the carrier TalkTalk have inadvertently released parts of the 020 0011 range to the general public,[12] with these numbers currently being in use.

Until July 2017, the 0500 range was used for some freephone services which were originally provided by Mercury Communications Ltd (now Cable & Wireless Worldwide).

These numbers were different from the rest of the 05 range in that they are only 9 digits in length after the 0 trunk code, e.g. 0500 007 007 (National Savings and Investments), 0500 2 88 2 91 (BBC Radio 2, 88 to 91 FM), 0500 600 600 (Crimewatch), 0500 600 700 (Watchdog[clarification needed]) and 0500 909 693 (BBC Radio 5 Live, 909 and 693 kHz).

Additionally, numbers in the range 0808 80x xxxx are reserved for not-for-profit helplines and as such are usually free to call from most mobile telephones.

They often do not qualify for discounts and bundled minutes, and can be prohibitively expensive when called from mobiles and payphones.

[43] Telecoms companies must inform their customers about their access charge for calling each number range.

The EU Consumer Rights Directive requires that many entities that held 084 and 087 numbers will no longer be allowed to use them.

[44][45] Since Britain left the EU the Directive as such no longer applies, but its provisions may have been incorporated into British law.

[needs update] Numbers in the 09xx range are charged at the highest rates of any calls within the United Kingdom, and are controlled by various regulations regarding their use.

[46] On the Isle of Man, both fixed (01624) and mobile phone (07624) numbers can be dialled locally in the six-digit format.

Ofcom has also reserved certain number ranges for use in media productions, such as radio and television dramas and films; so as to avoid the risk of people having genuine telephone numbers displayed and receiving unwanted calls.

[47][48] The Post Office even produced dial centre labels for use in advertisements and film / TV with a mythical exchange called VINcent plus four digits.

In Coronation Street, the fictional Manchester suburb of Weatherfield uses the unallocated range 0161 715 xxxx.

[51][52][53]) Both numbers can be called from mobile phones with the keylock on or without entering the PIN where that would otherwise be required.

The chargeable number 101 was introduced for non-urgent crime and community safety calls on a trial basis in 2006.

In Wales, the scheme was taken forward by all four police forces, who adopted the number for non-emergency calls on a permanent basis in early 2009.

The operator is obtained via 100 from landlines, while directory enquiries, formerly 192, is now provided in the 118xxx range, (not to be confused with 0118, the area code for Reading.)

The National Health Service (NHS) can be reached on 111 for non-emergency calls (from landlines and mobiles only).

[55] Two telephone helplines within the regular code space have only eight digits: 0800 11 11 for ChildLine and 0845 4647 for NHS Direct in Wales.

Before this, exchanges in "Director" areas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) dialled 846 (TIM), later changing to 123; main exchanges in "non-Director" areas originally used "952", later changing to "80" with the introduction of STD and eventually to "8081" as other recorded services were introduced on 80X1 codes.

Short codes beginning with 1 are reserved for telecom service providers' own functionality; some of the most well-known are codes for use with Caller Display: Many fixed-line telephone subscribers, e.g. of BT,[57] Virgin Media,[58] SkyTalk, TalkTalk, and PlusNet, have the opportunity to use an automated messaging service which takes messages when the called number is either engaged ("busy") or not answered within a given time.

For fixed-line users, it is possible to override the carrier pre-selection (CPS) on a per-call basis, dialling a special code before the number, e.g. 1280 for BT, 1664 for LowerCall, or 1844 for Daisy.