Postcodes in the United Kingdom

AB postcode areaAL postcode areaB postcode areaBA postcode areaBB postcode areaBD postcode areaBH postcode areaBL postcode areaBN postcode areaBR postcode areaBS postcode areaBT postcode areaBT postcode areaCA postcode areaCB postcode areaCF postcode areaCH postcode areaCM postcode areaCO postcode areaCR postcode areaCT postcode areaCV postcode areaCW postcode areaDA postcode areaDD postcode areaDE postcode areaDG postcode areaDH postcode areaDL postcode areaDN postcode areaDT postcode areaDY postcode areaE postcode areaEC postcode areaEH postcode areaEN postcode areaEX postcode areaEX postcode areaFK postcode areaFY postcode areaG postcode areaGL postcode areaGU postcode areaGY postcode areaHA postcode areaHD postcode areaHG postcode areaHP postcode areaHR postcode areaHS postcode areaHU postcode areaHX postcode areaIG postcode areaIM postcode areaIP postcode areaIV postcode areaJE postcode areaKA postcode areaKA postcode areaKT postcode areaKW postcode areaKW postcode areaKY postcode areaL postcode areaLA postcode areaLD postcode areaLE postcode areaLL postcode areaLN postcode areaLS postcode areaLU postcode areaM postcode areaME postcode areaMK postcode areaML postcode areaN postcode areaNE postcode areaNG postcode areaNN postcode areaNP postcode areaNR postcode areaNW postcode areaOL postcode areaOX postcode areaPA postcode areaPA postcode areaPA postcode areaPE postcode areaPH postcode areaPH postcode areaPH postcode areaPH postcode areaPL postcode areaPO postcode areaPR postcode areaRG postcode areaRH postcode areaRM postcode areaS postcode areaSA postcode areaSE postcode areaSG postcode areaSK postcode areaSL postcode areaSM postcode areaSN postcode areaSO postcode areaSP postcode areaSR postcode areaSS postcode areaST postcode areaSW postcode areaSY postcode areaTA postcode areaTD postcode areaTF postcode areaTN postcode areaTQ postcode areaTR postcode areaTR postcode areaTS postcode areaTW postcode areaUB postcode areaW postcode areaWA postcode areaWC postcode areaWD postcode areaWF postcode areaWN postcode areaWR postcode areaWS postcode areaWV postcode areaYO postcode areaZE postcode areaZE postcode areaZE postcode areaZE postcode areaAL postcode areaBR postcode areaCM postcode areaCR postcode areaDA postcode areaE postcode areaEC postcode areaEN postcode areaGU postcode areaHA postcode areaIG postcode areaKT postcode areaN postcode areaNW postcode areaRM postcode areaSE postcode areaSL postcode areaSM postcode areaSW postcode areaTN postcode areaTW postcode areaUB postcode areaW postcode areaWC postcode areaWD postcode areaWD postcode areaBB postcode areaBD postcode areaBL postcode areaCH postcode areaCW postcode areaDE postcode areaDN postcode areaFY postcode areaHD postcode areaHG postcode areaHX postcode areaL postcode areaLA postcode areaLL postcode areaLL postcode areaLS postcode areaM postcode areaNG postcode areaOL postcode areaPR postcode areaS postcode areaSK postcode areaST postcode areaWA postcode areaWF postcode areaWN postcode areaYO postcode areaMap of the United Kingdom and Crown dependencies showing postcode area boundaries
Map of postcode areas in the United Kingdom and Crown dependencies, with links to each postcode area

Postal codes used in the United Kingdom are known as postcodes (originally postal codes).[1] They are alphanumeric and were adopted nationally between 11 October 1959 and 1974, having been devised by the GPO (Royal Mail).[2] A full postcode is known as a "postcode unit" and designates an area with a number of addresses or a single major delivery point.[1]

The structure of a postcode is that of two alphanumeric codes each made up of three (or four) characters. First, one or two letters indicate the city or region, followed by one or two digits signifying a locality/ area or neighbourhoods in that city/ region. This is followed by a space and then a number and two letters which are allocated to streets, and sides of the street. The central part of the city or region a.k.a the city centre/ town centre will have the number 1 designation alongside the city code e.g B1 (Birmingham), LS1 (Leeds), M1 (Manchester) - all central addresses. As a general rule, a higher number indicates distance from that centre.See postcode area

Postcodes have been adopted for a wide range of purposes in addition to aiding the sorting of the mail: for calculating insurance premiums, designating destinations in route planning software and as the lowest level of aggregation in census enumeration. The boundaries of each postcode unit and within these the full address data of currently about 29 million addresses (delivery points) are stored, maintained and periodically updated in the Postcode Address File database.[1]

The initial system of named postal districts, developed in London and other large cities from 1857, evolved towards the present form: in 1917 London was split into broad numbered subdivisions, and this extended to the other cities in 1934. After the reorganisation of London in the 1960s, many parts of the city now lie outside the traditional postcode zone. This includes, but is not limited to, large parts of the "TW" "KT" "SM" "CR" "HA" and "UB" postcode areas, among a few others.

The postcode of GCHQ is GL51 0EX, where GL signifies the postal area of Gloucester. The postal town refers to a wide area and does not relate to a specific town, county or region. GL51 is one of the postcodes for the town of Cheltenham (in Gloucestershire) which is where GCHQ is located.

Theoretically, deliveries can reach their destination using the house number and post code alone, however this is against Royal Mail guidelines who request a full address at all times.

History

Earlier postal districts

London

The London post town covers 40% of Greater London. On inception (in 1857/8) it was divided into ten postal districts: EC (East Central), WC (West Central), N, NE, E, SE, S, SW, W, and NW. The S and NE sectors were later abolished. In 1917, as a wartime measure to improve efficiency, these were subdivided with a number applied to each sub-district, with the area served directly by the district head office as "1" with the others allocated alphabetically by delivery office, leading to N2 East Finchley delivery office, N3 Finchley delivery office, N4 Finsbury Park delivery office. These divisions changed little, usually only changed for operational efficiency.

Some older road signs in Hackney still indicate the North East (NE/N.E.) sector/district.

Other large towns

Street name signs on Birdbrook Road, Great Barr, Birmingham, showing old "Birmingham 22" (top) and modern "B44" postcodes.

Following the successful introduction of postal districts in London, the system was extended to other large towns and cities. Liverpool was divided into Eastern, Northern, Southern and Western districts in 1864/65, and Manchester and Salford into eight numbered districts in 1867/68.[3]

In 1917, Dublin – then still part of the United Kingdom – was divided into numbered postal districts. These continue in use in a modified form by An Post, the postal service of the Republic of Ireland. In 1923, Glasgow was divided in a similar way to London, with numbered districts preceded by a letter denoting the compass point (C, W, NW, N, E, S, SW, SE).[3]

In January 1932 the Postmaster General approved the designation of some predominantly urban areas into numbered districts.[3] In November 1934 the Post Office announced the introduction of numbered districts (short postal codes) in "every provincial town in the United Kingdom large enough to justify it". Pamphlets were issued to each householder and business in ten areas notifying them of the number of the district in which their premises lay. The pamphlets included a map of the districts, and copies were made available at local head post offices. The public were "particularly invited" to include the district number in the address at the head of letters.[4] A publicity campaign in the following year encouraged the use of the district numbers. The slogan for the campaign was "For speed and certainty always use a postal district number on your letters and notepaper". A poster was fixed to every pillar box in the affected areas bearing the number of the district and appealing for the public's co-operation. Every post office in the numbered district was also to display this information. Printers of Christmas cards and stationery were requested to always include district numbers in addresses, and election agents for candidates in the upcoming general election were asked to ensure they correctly addressed the 100 million items of mail they were expected to post. Businesses were issued with a free booklet containing maps and listings of the correct district number for every street in the ten areas.[5]

The ten areas were:[5]

For example, Toxteth was Liverpool 8. A single numbering sequence was shared by Manchester and Salford: letters would be addressed to Manchester 1 or Salford 7 (lowest digits, respectively). Some Birmingham codes were sub-divided with a letter, such as Great Barr, Birmingham 22 or Birmingham 22a,[6] as can still be seen on many older street-name signs.

Modern postcode system

The Post Office experimented with electromechanical sorting machines in the late 1950s.[7] These devices presented an envelope to an operator, who would press a button indicating which bin to sort the letter into. Postcodes were suggested to increase the efficiency of this process, by removing the need for the sorter to remember the correct sorting for as many places.[8] In January 1959 the Post Office analysed the results of a survey on public attitudes towards the use of postal codes, choosing a town in which to experiment with codes. The envisaged format was a six-character alphanumeric code with three letters designating the geographical area and three numbers to identify the individual address.[9] On 28 July Ernest Marples, the Postmaster General, announced that Norwich had been selected, and that each of the 150,000 private and business addresses would receive a code by October. Norwich had been selected as it already had eight automatic mail sorting machines in use.[10] The original Norwich format consisted of "NOR" followed by a space, then a two-digit number (which, unlike the current format, could include a leading zero) and a single final letter (instead of the two final letters in the current format).[11]

In October 1965, Tony Benn as Postmaster General[12] announced that postal coding was to be extended to the rest of the country in the next few years.[13]

On 1 May 1967 postcodes were introduced in Croydon. The many postcodes for central Croydon began with "CRO", and those of the surrounding post towns with outward codes (the characters before the space) CR2, CR3 and CR4. The uniform system of a set of three final characters, after the space, such as 0AA, known as the inward code, was adopted. This was to be the beginning of a ten-year plan, costing an estimated £24 million. Within two years it was expected that full coding would be used in Aberdeen, Belfast, Brighton, Bristol, Bromley, Cardiff, Coventry, Manchester, Newcastle upon Tyne, Newport, Reading, Sheffield, Southampton and the Western district of London.[14] By 1967, codes had been introduced to Aberdeen, Southampton, Brighton and Derby.[15] In 1970, codes were introduced to the London W and North Western postal districts.[16] In December 1970 much Christmas mail was postmarked with the message "Remember to use the Postal Code", although codes were used to sort mail in only a handful of sorting offices.[17]

During 1971, occupants of addresses began to receive notification of their postcode. Asked in the House of Commons about the completion of the coding exercise, the Minister of State for Posts and Telecommunications (whose role superseded that of Postmaster General in 1969), Sir John Eden, stated that it was expected to be completed during 1972.[18] The scheme was finalised in 1974 when Norwich was completely re-coded but the scheme tested in Croydon was sufficiently close to the final design for it to be retained, with CRO standardised as CR0 (district zero), thus removing the need to create a CR1 district.[3]

A quirk remained: the central Newport area was allocated NPT, at a similar time to Croydon becoming CRO, and surrounding areas were, as today, allocated NP1–NP8. NPT lasted until the end of 1984 when it was recoded NP9.[19]

Girobank's GIR 0AA, the last domestic postcode with a fully alphabetical outward code, no longer exists in the Royal Mail's PAF system,[20] but remains in active use by the bank's owners, currently Santander UK.[21]

Adaptation of earlier systems into national system

When the national postcode system was introduced, many existing postal districts were incorporated into it, so that postcodes in Toxteth (Liverpool 8) start with L8. The districts in both Manchester and Salford gained M postcodes, so Salford 7 became M7 and so on (and similarly in Brighton and Hove, both using the prefix BN). The old coding lives on in a small number of street signs with (for example) "Salford 7" at the bottom. In other cases, the district numbers were replaced with unrelated numbers. In Glasgow many of its G-prefixed numbers are not used as C1 became G1, W1 became G11, N1 became G21, E1 became G31, S1 became G41, SW1 became G51, and so on. In London (as postally defined) 1917-created postal districts are mapped unchanged to those of today but its much enlarged administrative area, Greater London was created in April 1965. From that month the remaining 60% of Greater London's area has postcodes referring to 13 other post towns. Additionally, there were too few postcodes to adequately cover districts in central London (particularly in the WC and EC areas), so these were subdivided with a letter suffix rather than being split into new numbered districts, so as to retain the familiar codes.

GB postcodes available as OpenData

Prior to 1 April 2010 the Royal Mail licensed use of the postcode database for a charge of about £4000 per year.[22] Following a campaign and a government consultation in 2009[23] the Ordnance Survey released Code-Point Open, detailing each current postcode in Great Britain together with a geo-code for re-use free of charge under an attribution-only licence Open Government Licence as part of OS OpenData.

Postcodes linked to a variety of UK geographies

The Office for National Statistics (ONS Geography) maintains and publishes a series of freely available, downloadable postcode products that link all current and terminated UK postcodes to a range of administrative, health, statistical and other geographies using the Code-Point Open grid reference.

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