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{{Short description|none}}
{{Use British English|date=October 2019}}
{{Use dmy dates|date=May 2024}}
{{Postcode areas imagemap|___location=right}}
[[Postal code]]s used in the United Kingdom, [[British Overseas Territories]] and [[Crown dependencies]] are known as '''postcodes''' (originally, postal codes).<ref name=guide>{{Cite book| author=[[Royal Mail]] | publisher =Royal Mail Group | edition=4 | title =Address Management Guide |date=October 2004}}</ref> They are [[alphanumeric]] (the UK is one of only 11 countries or territories to use alphanumeric codes out of the 160 postcode-using members of the ICU) and were adopted nationally between 11 October 1959 and 1974, having been devised by the [[General Post Office]] ([[Royal Mail]]).<ref name="Short history">{{Cite news|url=https://www.independent.co.uk/money/mortgages/a-short-history-of-the-postcode-751884.html|title=A short history of the postcode|date=1 January 2005|work=The Independent|access-date=3 October 2009}}</ref>
The system was designed to aid in sorting [[mail]] for delivery. It uses alphanumeric codes to designate geographic areas. A full postcode identifies a group of addresses (typically around 10) or a major delivery point. It consists of an outward code and an inward code. The outward code indicates the area and district, while the inward code specifies the sector and delivery point.
The initial postcode system evolved from named postal districts introduced in London and other large cities from 1857. Districts in London were then subdivided in 1917, with each allocated a distinct number. This had extended to other cities by 1934. The territory of the UK is broken down into 121 postcode areas. Each postcode area contains multiple post towns and districts. Postcode areas are mnemonically named after the area's major post town (such as TR for '''TR'''uro) although some are named after smaller towns or regional areas.
Postcodes have since been additionally used in various applications. Postcodes help calculate [[insurance]] premiums, designate destinations in route planning software, and serve as aggregation units in [[census]] enumeration. The Postcode Address File (PAF) database stores and updates the boundaries and address data for around 29 million addresses, ensuring accurate delivery and extensive utility beyond postal services. The PAF is managed by Royal Mail and its use is overseen by the independent PAF Advisory Board.
== Overview ==
=== Structure ===
A full postcode is known as a "postcode unit" and designates an area with several addresses or a single major delivery point.<ref name=guide/> The structure of a postcode is two alphanumeric codes that show, first, the post town and, second, a small group of addresses in that post town. The first alphanumeric code (the outward code or outcode) has between two and four characters and the second (the inward code or incode) always has three characters. The outcode indicates the postcode area and postcode district. It consists of one or two letters, followed by one digit, two digits, or one digit and one letter. This is followed by a space and then the incode which indicates the postcode sector and delivery point (usually a group of around 10-15 addresses,{{citation needed|date=December 2024}} but can vary). The incode (always three characters), starts with a number (denoting a sector within the district), and ends with two letters (denoting delivery points which are allocated to streets, sides of a street or individual properties).
=== Postcode area names ===
Postcode areas are usually, but not always, named after a major town or city – such as B for Birmingham. Some are named after a smaller town (e.g. Southall postcode area is UB after Uxbridge) or a combination of towns (e.g. SM appears to be named after '''S'''utton and '''M'''orden). A small number are regional – such as HS for the Outer '''H'''ebride'''s''', FY for '''Fy'''lde (the region around Blackpool) and ME for the '''Me'''dway conurbation, with Rochester as its main post town. In the case of London (a Post Town), there is not a single "London" postcode area (such as "LO"); rather there are eight (N, E, EC, SE, SW, W, WC and NW) reflecting the preceding system for coding London based on compass points. In the case of Northern Ireland, the entire province has a single postcode area BT (named for '''B'''elfas'''t'''). The mnemonic features various combinations - most commonly, first two letters (CH for '''CH'''ester); first and last letters (BH for '''B'''ournemout'''H'''); first and key syllable letters (IV for '''I'''n'''V'''erness). Postcodes generally do not align with historical county or local authority boundaries, and can also cross national boundaries (e.g. the CH and TD postcode areas).
=== Postcode districts and numbering ===
Each postcode area contains a number of post towns and postcode districts. All districts are defined by either one or two digits (AA9 or AA99); in London (only), some districts are additionally defined by one digit and one letter (A9A or AA9A).
As a general rule, postcode districts are numbered consecutively from 1, with the exceptions of:
* numbering from 0: BL, BS, CM, CR, FY, HA, PR, SL and SS
* numbering from 10: AB, LL, SO
In most postcode areas, the central part of the post town for which the postcode area is named will have the district number 1 e.g. B1 (central Birmingham). In addition, the postcode "aa1 1AA" was often allocated to the crown or principal post office in the central postcode district.
The allocation of postcode district numbers, in most cases, is from the main post town outward e.g. Halifax which has seven districts numbered consecutively HX1 to HX7, but this is not universal. There are a number of different numbering allocations and exceptions:
*'''geographical direction:''' e.g. the Outer Hebrides postcode area HS, where the districts are numbered from north to south
*'''geographic reality''': particularly in larger postcode areas, the scale of the districts discourages consecutive numbering e.g. in the NE postcode area, NE50 to NE60 are not allocated due to the substantial distance between NE49 (Haltwhistle) and the next district to be numbered (Morpeth, which was numbered NE61 rather than NE50), recognising the geographic separation of districts in the west (up to NE49) from those to the north (NE61 upwards).
*'''clusters:''' particularly if the postcode area encompasses several major towns or cities (e.g. S postcode area with Sheffield S1–S36, Chesterfield S40–S49, Rotherham S60–S65, Barnsley S70–S75 and Worksop S80–S81)
* '''alphabetical order''' of district sub-offices: used only in London postcode areas (e.g. E2 is Bethnal Green, E3 is Bow, E4 is Chingford etc., which results in intuitive anomalies such as SE1 and SE2 being far from neighbours, with SE1 being large part of Central London south of the Thames (Waterloo and the borough of Southwark) and SE2 covering Abbey Wood at the far eastern end of the Elizabeth Line (in the boroughs of Greenwich and Bexley).
* '''earlier districts:''' where preceding postal districts have been adopted into the current system (such as Glasgow's "compass points") or translated from the postcode pilot phase (such as Croydon's CRO becoming CR0 rather than CR1).
* '''new postcode districts:''' new postcode districts are occasionally created, usually due to increased demand for addresses following housing/business development and exhaustion of available postcodes for the existing district. There appear to be no clear rules for numbering new districts. If no sequential numbers are available, then new non-consecutive numbers are allocated. For example, in the [[CV postcode area]], the CV47 district was formed in 1999 from parts of the CV23 and CV33 districts, where the highest numbered district then allocated was CV37.
* '''transfer of postcode districts''': postcode districts can be transferred for operational reasons e.g. PH49 and PH50 postcode districts which resulted from the transfer and recoding of PA39 and PA40 districts (PH39 and PH40 were already allocated although PH45–PH48 were not allocated). This also occurred with the creation of the HS postcode area, the only new geographic postcode area created since 1973, from the previous PA80 to PA87 districts.
London uniquely uses letters for subdivisions of some of its postcode districts (E1, N1, W1, WC1, WC2, EC1–EC4, NW1, SE1, SW1) with letters used substantively in three areas: W (W1), WC (WC1 and WC2) and EC (EC1–EC4), these being the most central areas with the densest concentration of addresses. These are effectively postcode districts in their own right, and could have been given double digit numbers (e.g. for WC in the range WC10-WC19 and WC20-WC29). The districts are geographically extremely small. Using double-digit numbering might have encountered resistance due to their "micro-size" and also due to the long-standing use of "WC1" etc. which signified in some cases a cultural or wealth status which may have been diluted or lost if re-coded from WC1 to, say, WC15. Even if London had dropped the initial compass points systems to create a single post code area, the challenge of the large number of districts (169) would have required a bespoke numbering system:
{| class="wikitable"
!Area
!Geographic<br>districts<br>(total N/NN/aN)
!(aN combination)<br>{{clarify|date=July 2025}}
!Non-geographic<br> districts<br>(total)
!(aN combination)
|-
|E
|20
|1
|2
|0
|-
|EC
|23
|23
|4
|3
|-
|N
|23
|1
|2
|1
|-
|NW
|11
|0
|2
|1
|-
|SE
|28
|0
|1
|1
|-
|SW
|27
|8
|0
|0
|-
|W
|25
|12
|1
|1
|-
|TOTAL
|157
|45
|12
|7
|}
Accordingly, many postcode districts are not physically contiguous, despite the inference from their numbering. Likewise, the centrality of a postcode district within a postcode area cannot be reliably inferred from the postcode alone. See [[postcode area]].
=== Postcode use ===
Postcodes have been adopted for a wide range of purposes in addition to aiding the sorting of 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.<ref name=guide/>
Theoretically, deliveries can reach their destination using the house number (or name if the house has no number) and postcode alone; however, this is against Royal Mail guidelines, which request the use of a full address.<ref>{{Cite web|url=https://personal.help.royalmail.com/app/answers/detail/a_id/81/~/how-to-address-your-mail-(clear-addressing)|title=How to address mail clearly, guide to clear letter addressing|website=personal.help.royalmail.com}}</ref>
==History==
===Earlier postal districts===
====London====
{{main|London postal district}}
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, each postal district was subdivided into sub-districts each identified by a number; the area served directly by the district head office was allocated the number 1; the other numbers were allocated alphabetically by delivery office, e.g. N2 East Finchley delivery office, N3 Finchley delivery office, N4 Finsbury Park delivery office etc. Since then these sub-districts have changed little.
Some older road signs in Hackney still show the North East (NE) sector/district.
====Other large cities and towns====
[[Image:BirdbrookRoadSigns.jpg|thumb|right| Street name signs on Birdbrook Road, Great Barr, Birmingham, showing old "Birmingham 22" postal district (top) and modern "B44" postcode.]]
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.<ref name=bpma/>
In 1917, [[Dublin]]—then still part of the United Kingdom—was divided into [[List of Dublin postal districts|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).<ref name=bpma/>
In January 1932 the Postmaster General approved the designation of some predominantly urban areas into numbered districts.<ref name=bpma/> 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.<ref name=times1934>{{Cite news|title=Numbered P.O. Districts in Country Towns. Aid To Accurate Delivery |work=[[The Times]] |page=14 |date=20 November 1934 }}</ref>
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 agent]]s for candidates in the upcoming [[1935 United Kingdom general election|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.<ref name=times1935>{{Cite news|title=Postal District Numbers Appeal For Use in Addresses|work=[[The Times]] |page=14 |date=29 October 1935}}</ref>
The ten areas were:<ref name=times1935/>
*[[Birmingham]]
*[[Brighton]]/[[Hove]]
*[[Bristol]]
*[[Edinburgh]]
*[[Glasgow]]
*[[Leeds]]/[[Bradford]]
*[[Liverpool]]
*[[Manchester]]/[[Salford]]
*[[Newcastle upon Tyne]]
*[[Sheffield]]
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'',<ref name=Will>{{Cite web |url=http://www.jacomb.com/w1951_1960.htm |archive-url=https://web.archive.org/web/20070208065042/http://www.jacomb.com/w1951_1960.htm |url-status=dead |archive-date=8 February 2007 |title=1951 will, using address in "Birmingham 22a" |publisher=Jacomb.com |access-date=1 September 2010 }}</ref> 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.<ref>[http://news.bbc.co.uk/1/hi/uk/8288148.stm "Modern postcodes are 50 years old"], [[BBC News]], 2 October 2009</ref> 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.<ref name=new_scientist>''New Scientist'', 21 July 2007, p16</ref> 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.<ref name=times_150189>"Postal codes to speed up mail", ''The Times'', 15 January 1959</ref> On 28 July [[Ernest Marples]], the [[Postmaster General of the United Kingdom|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.<ref name=times_290659>"Norwich to use postal codes – Experimenting in automation", ''The Times'', 29 July 1959</ref> 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 finally a single letter (instead of the two final letters in the current format).<ref name="norexamples">Examples of Norwich NOR postcodes in the old format: "NOR 03Z", "NOR 66F", "NOR 83B", "NOR 05S". {{London Gazette |issue=45542 |date=13 December 1971 |page=13658}}</ref>
In October 1965, [[Tony Benn]] as Postmaster General<ref>{{cite web |url = https://www.bbc.co.uk/news/blogs-magazine-monitor-26575843 |title = Five lesser-spotted things Tony Benn gave the UK |date = 14 March 2014 |publisher = BBC News |access-date= 13 May 2014 }}</ref> announced that postal coding was to be extended to the rest of the country in the next few years.<ref name=times_051065>"G.P.O. robot postman sorts 20,000 letters an hour", ''The Times'', 5 October 1965</ref>
On 1 May 1967 postcodes were introduced in [[Croydon]]. The many postcodes for central Croydon began with "CRO", while those of the surrounding [[post town]]s with 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, Wales|Newport]], [[Reading, Berkshire|Reading]], [[Sheffield]], [[Southampton]] and the [[W postcode area|Western district]] of London.<ref name=times_121066>"Someone, Somewhere in postal code", ''The Times'', 12 October 1966</ref> By 1967, codes had been introduced to Aberdeen, Southampton, Brighton and [[Derby]].<ref name=times_040767>"Post Office plans faster service", ''The Times'', 4 July 1967</ref> In 1970, codes were introduced to the London Western and [[NW postcode area|North Western]] postal districts.<ref name=times_150870>"London in brief", ''The Times'', 15 September 1970</ref> 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 office]]s.<ref name=times_180171>"Inside the Post Office", ''The Times'', 18 January 1971</ref>
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), [[John Eden, Baron Eden of Winton|Sir John Eden]], stated that it was expected to be completed during 1972.<ref name=times_200472>"Postal code programme", ''The Times'', 20 April 1972</ref> 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.<ref name=bpma>[http://www.postalheritage.org.uk/history/downloads/BPMA_Info_Sheet_Postcodes_web.pdf Information Sheet: Postcodes] {{webarchive|url=https://web.archive.org/web/20090320052708/http://www.postalheritage.org.uk/history/downloads/BPMA_Info_Sheet_Postcodes_web.pdf |date=20 March 2009 }}, British Postal Museum and Archive</ref>
A quirk remained: the central Newport (Gwent) 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.<ref name="nptgazette">{{Cite web|url=http://www.london-gazette.co.uk/issues/49959/pages/17064/page.pdf|title=Borough of Newport (Kingsway) (Business Parking Places) Order 1985|last=Newport Borough Council|date=17 December 1984|work=The London Gazette (No. 49959)|publisher=HMSO|page=17064|access-date=5 October 2009}}</ref>
[[Girobank]]'s GIR 0AA was the last domestic postcode with a fully alphabetical outward code. That code no longer exists in the Royal Mail's PAF system, but was taken over by the bank's current owners, [[Santander UK]].<ref>{{cite news |last1=Manger |first1=Warren |title=40 facts about the postcode to mark 40th anniversary as vital part of daily life |url=https://www.mirror.co.uk/news/uk-news/40-facts-postcode-mark-40th-4113087 |access-date=12 May 2019 |agency=Mirror |date=26 August 2014}}</ref>
====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 following the transposition of the earlier compass point districts to "G" districts: 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 today despite Greater London, created in April 1965, covering a much larger administrative area. The London post town covers 40% of Greater London and 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 £4,000 per year.<ref name="planning">{{cite news|url=https://www.theguardian.com/technology/2009/oct/07/newly-asked-question-royal-mail-postzon|title=newspaper article on postcodes|author=Charles Arthur|date=10 October 2009|newspaper=The Guardian|___location=London|access-date=1 September 2010}}</ref> Following a campaign and a government consultation in 2009,<ref>{{Cite web|url=http://www.communities.gov.uk/publications/corporate/ordnancesurveyconsultation |title=DCLG: Policy options for geographic information from Ordnance Survey: Consultation |publisher=Communities.gov.uk |date=23 December 2009 |access-date=1 September 2010 |url-status=dead |archive-url=https://web.archive.org/web/20091230115507/http://www.communities.gov.uk/publications/corporate/ordnancesurveyconsultation |archive-date=30 December 2009}}</ref> 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.
==Formatting==
===Overview===
The postcodes are alphanumeric, and are (possibly uniquely) variable in length: ranging from six to eight characters (including a space). Each postcode is divided into two parts separated by a single space: the ''outward code'' and the ''inward code'' respectively. The ''outward code'' includes the ''postcode area'' and the ''postcode district'', respectively. The ''inward code'' includes the ''postcode sector'' and the ''postcode unit'' respectively. Examples of postcodes are "SW1W 0NY", "PO16 7GZ", "GU16 7HF", and "L1 8JQ".<ref>{{Cite web |title=SW1W 0NY Postcode - Greater London, England, UK |url=https://trackpostcode.uk/postcode/sw1w/0ny/ |access-date=2024-10-28 |website=trackpostcode.uk}}</ref>
{| class="wikitable" style="text-align: center; margin: 0 auto;"
!style="background:#87cefa; color: black;" colspan=4| POSTCODE
|- style="background:#ff4500; color: white;"
|colspan=2| Outward code
|colspan=2| Inward code
|- style="background:#ff4500; color: white;"
| Area || District || Sector || Unit
|- style="background:#0000cd; color: white;"
| SW || 1W || 0 || NY
|}
===Outward code===
The outward code is the part of the postcode before the single space in the middle. It is between two and four characters long. Examples of outward codes are "L1", "W1A", "RH1", "RH10" or "SE1P". A few outward codes are non-geographic, not divulging where mail is to be sent. These postcodes cannot be used for navigation purposes.
====Postcode area====
The [[postcode area]] is part of the outward code. The postcode area is either one or two characters long and is alphabetical, with there being 121 such areas. Examples of postcode areas are "L" for [[Liverpool]], "RH" for [[RH postcode area|Redhill]] and "EH" for [[Edinburgh]]. A postal area may cover a wide area, for example "RH" covers various settlements in eastern Surrey and north eastern West Sussex, and "BT" ([[Belfast]]) covers the whole of [[Northern Ireland]].
====Postcode district====
The [[postcode district]] is one digit, two digits or a digit followed by a letter.
===Inward code===
The inward code is the part of the postcode after the single space in the middle. It is three characters long. The inward code assists in the delivery of post within a postal district. Examples of inward codes are "0NY", "7GZ", "7HF", or "8JQ".<ref name="Postcodes & Addresses Explained" />
====Postcode sector====
The postcode sector is made up of a single digit (the first character of the inward code). Most postcode areas do not use all of the sectors 0–9 in order to allow for the possibility of more sectors being added in the face of new development. Rather, in the initial allocation of postcodes, neighbouring postcode districts were often assigned to contain the ten sectors between them. For example, across the three postcode districts [[BS postcode area|BS6-8]] (which are next to each other in north west [[Bristol]]), sectors 1-4 were assigned to BS8, sectors 5-7 were assigned to BS6, and sectors 8-9 and 0 were assigned to BS7 (more recent changes have resulted in all three of those areas now having a sector 9).<ref>{{cite web |last1=Bell |first1=Chris |title=BS Postcode Area Bristol |url=https://www.doogal.co.uk/UKPostcodes?Search=BS |website=Doogal |access-date=1 September 2024}}</ref>
====Postcode unit====
The postcode unit is two characters added to the end of the postcode sector. A postcode unit generally represents a street, part of a street, a single address, a group of properties, a single property, a sub-section of the property, an individual organisation or (for instance [[Driver and Vehicle Licensing Agency]]) a subsection of the organisation. The level of discrimination is often based on the amount of mail received by the premises or business.
===Validation===
The format is as follows, where '''A''' signifies a letter and '''9''' a digit:
{| class="wikitable"
|-
! Format !! Coverage !! Example
|-
! style="text-align:left; white-space:nowrap;" | AA9 9AA
| rowspan="2" |All postcodes except those listed below
| style="white-space:nowrap;" | CR2 6XH
|-
! style="text-align:left; white-space:nowrap;" | AA99 9AA
| style="white-space:nowrap;" | DN55 1PT
|-
! style="text-align:left; white-space:nowrap;" | A9 9AA
| rowspan="2" |B, E, G, L, M, N, S, W
| style="white-space:nowrap;" | M1 1AE
|-
! style="text-align:left; white-space:nowrap;" | A99 9AA
| style="white-space:nowrap;" | B33 8TH
|-
! style="text-align:left; white-space:nowrap;" | A9A 9AA
| London postcode districts: E1, N1, W1
| style="white-space:nowrap;" | W1A 0AX
|-
! style="text-align:left; white-space:nowrap;" | AA9A 9AA
| London postcodes: WC postcode area; and districts EC1–EC4, NW1W, SE1P, SW1
| style="white-space:nowrap;" | EC1A 1BB
|}
Notes:
* As all formats end with 9AA, the first part of a postcode can easily be extracted by ignoring the last three characters.
* Areas with only single-digit districts: BL, BR, FY, HA, HD, HG, HR, HS, HX, JE, LD, SM, SR, WC, WN, ZE (although WC is always subdivided by a further letter, e.g. WC1A)
* Areas with only double-digit districts: AB, LL, SO (for AB this arose from decoding of the original five districts AB1-AB5 by adding a second digit, to enable additional postcodes to become available, thus AB1 was divided into AB10-AB16).
* Areas with a district '0' (zero): BL, BS, CM, CR, FY, HA, PR, SL, SS (BS is the only area to have both a district 0 and a district 10)
* The following central London single-digit districts have been further divided by inserting a letter after the digit and before the space: EC1–EC4 (but not EC50), SW1, W1, WC1, WC2 and parts of E1 (E1W), N1 (N1C and N1P), NW1 (NW1W) and SE1 (SE1P).
* The letters ''Q'', ''V'' and ''X'' are not used in the first position.
* The letters ''I'', ''J'' and ''Z'' are not used in the second position.
* The only letters to appear in the third position are ''A'', ''B, C, D, E, F, G, H, J, K, P, S, T, U'' and ''W'' when the structure starts with A9A.
* The only letters to appear in the fourth position are ''A, B, E, H, M, N, P, R, V, W, X'' and ''Y'' when the structure starts with AA9A.
* The final two letters do not use ''C, I, K, M, O'' or ''V'', so as not to resemble digits or each other when hand-written.
* Postcode districts are one of ten digits: 0 to 9, with 0 only used once 9 has been used in a post town, save for Croydon (see above).
* Postcode sectors can also be one of ten digits: 0 to 9, though in some postcode areas the 0 is the beginning of the sequence (for example in LE), while in other areas it is the end of the sequence (i.e. 10, as in CV).
A postcode can be validated against a table of all 1.7 million postcodes in [https://www.ordnancesurvey.co.uk/products/code-point-open Code-Point Open]. The full delivery address including postcode can be validated against the [[Royal Mail]] [[Postcode Address File]] (PAF), which lists 29 million valid delivery addresses,<ref name=bbc_50>[http://news.bbc.co.uk/1/hi/uk/7803267.stm Postcodes to celebrate 50th year] [[BBC News]], 30 December 2008</ref> constituting most (but not all) addresses in the UK.<ref>{{cite web|
title=Falsehoods programmers believe about addresses|
url=http://www.mjt.me.uk/posts/falsehoods-programmers-believe-about-addresses/|
author=Michael Tandy|website=Mjt.me.uk|access-date=8 October 2017}}</ref> A [[regular expression]] for validating UK postcodes is specified in the [[British Standards]] document BS 7666.<ref>{{cite web|url=https://assets.publishing.service.gov.uk/media/632b07338fa8f53cb77ef6b8/WS02_LRS_Web_Services_Interface_Specification_v6.4.pdf|title=LRS Web Services Interface Specification|publisher=[[Education and Skills Funding Agency]]|date=September 2022|at=Appendix D|access-date=17 July 2024}}</ref>
===Post towns===
All or part of one or more postcode districts are grouped into [[post town]]s.<ref name="Guide">{{Cite book |title=Address Management Guide |edition=5th |publisher=Royal Mail Group plc |date=March 2007 |url=http://www.royalmail.com/marketing-services/address-management-unit/address-data-products/address-management-guide |access-date=25 October 2012}}</ref> Larger post towns may use more than one postcode district, for example Crawley uses RH10 and RH11. In a minority of cases, a single number can cover two or more post towns – for example, the WN8 district includes Wigan and Skelmersdale post towns; and the GL17 district contains five post towns.
==Special cases==
{{anchor|Special Cases}}
===Crown dependencies===
The [[Channel Islands]] and the [[Isle of Man]] established their own postal administrations separate from the UK in 1969. Despite this, they adopted the UK-format postcodes in 1993–94: [[Bailiwick of Guernsey|Guernsey]] using [[GY postcode area|GY]], the Isle of Man using [[IM postcode area|IM]], and [[Jersey]] using [[JE postcode area|JE]].<ref name="newareas">[https://publications.parliament.uk/pa/cm200203/cmhansrd/vo021217/text/21217w16.htm Written Answer <nowiki>[87341]</nowiki>], House of Commons Hansard, 17 December 2002, column 739W.</ref>
The independent jurisdiction of [[Sark]] was assigned a unique postcode district GY10 in 2011 to differentiate it from [[Alderney]]. The CEO of Guernsey Post, Boley Smillie, said "this has been a long time coming" and "... Sark should have had its own identity back then [when postcodes were adopted in 1993]".<ref>{{Cite news|url=https://www.bbc.co.uk/news/world-europe-guernsey-12121380|title=Sark gets own GY10 postcode after split from Alderney|date=7 January 2011|publisher=BBC News|access-date=6 August 2017}}</ref>
===British Overseas Territories===
{{More citations needed section|date=January 2021}}
Some of the [[British Overseas Territories]] have postcodes that broadly follow the format of the UK postcode system or, in Gibraltar's case, adopts the UK format:
{| class="wikitable"
|-
!Postcode !! Location
|-
|ASCN 1ZZ<ref name="MercoPress" />|| [[Ascension Island]]
|-
|BBND 1ZZ<ref name="UPU">[https://www.upu.int/UPU/media/upu/documents/PostCode/General-Addressing-Issues.pdf General Addressing Issues], Universal Postal Union</ref> || [[British Indian Ocean Territory]]
|-
|BIQQ 1ZZ<ref name="WalesOnline"/> || [[British Antarctic Territory]]
|-
|FIQQ 1ZZ<ref name="WalesOnline">[https://www.walesonline.co.uk/news/uk-news/falkland-postcode-unlocks-internet-2485265 Falkland postcode unlocks internet], [[WalesOnline]], 20 May 2003</ref> || [[Falkland Islands]]
|-
|GX11 1AA<ref name="gx111aa"/> || [[Gibraltar]]
|-
|PCRN 1ZZ<ref name="UPU" />|| [[Pitcairn Islands]]
|-
|SIQQ 1ZZ<ref name="WalesOnline" /> || [[South Georgia and the South Sandwich Islands]]
|-
|STHL 1ZZ<ref name="MercoPress">[https://en.mercopress.com/2003/05/19/rammell-welcomes-new-postcode-for-the-falkland-islands Rammell welcomes new Postcode for the Falkland Islands], MercoPress, 19 May 2003</ref> || [[Saint Helena]]
|-
|TDCU 1ZZ<ref name=bbc_tdcu>{{cite news |url=http://news.bbc.co.uk/1/hi/uk/4129636.stm |title=First postcode for remote UK isle |publisher=[[BBC News]] |date=7 August 2005}}</ref> || [[Tristan da Cunha]]
|-
|TKCA 1ZZ<ref name=upu>{{cite web |url=http://www.upu.int/post_code/en/countries/TCA.pdf |archive-url=https://web.archive.org/web/20060111192508/http://www.upu.int/post_code/en/countries/TCA.pdf |archive-date=2006-01-11 |url-status=live |title=Turks and Caicos Islands |website=Bureau International UPU}}</ref> || [[Turks and Caicos Islands]]
|}
These were introduced because mail was often sent to the wrong place, e.g., to St Helena instead of [[St Helens, Merseyside]]<ref>[https://www.standard.co.uk/hp/front/christmas-card-s-15-000mile-trip-after-posties-misread-address-7188682.html Christmas card's 15,000-mile trip after posties misread address], ''[[Evening Standard]]'', 28 March 2007</ref> or [[St Helens, Isle of Wight]].<ref>[https://www.countypress.co.uk/news/17551983.christmas-card-sent-wroxall-st-helens-finally-arrives-mistakenly-sent-remote-tropical-island-st-helena/ Christmas card sent from Wroxall to St Helens finally arrives after being mistakenly sent to remote tropical Island, St Helena], ''[[Isle of Wight County Press]]'', 5 April 2019</ref> and to [[Edinburgh]] instead of Edinburgh, [[Tristan da Cunha]], and many online companies would not accept addresses without a postcode.<ref name=bbc_tdcu /> Mail from the UK continues to be treated as international, not inland, and sufficient postage must be used.<ref>[https://www.royalmail.com/sites/royalmail.com/files/2021-03/royal-mail-our-prices-april-2021.pdf Our prices – Your handy guide to our UK and International parcel and letter service prices], [[Royal Mail]], 1 January 2021</ref>
[[Bermuda]] has developed its [[postal codes in Bermuda|own postcode system]], with unique postcodes for street and PO Box addresses,<ref name="bpo">{{cite web|url=http://www.bpo.bm/postalcodes.aspx?activemenu=40&sub=26|website=bpo.bm|title=Bermuda Post Office|access-date=31 July 2017}}</ref> as have the [[Cayman Islands]],<ref>{{Cite web |url=http://www.caymanpost.gov.ky/portal/page?_pageid=1327,1736998&_dad=portal&_schema=PORTAL |title=Cayman Islands Postal Service Postcode Finder |publisher=Caymanpost.gov.ky |access-date=1 September 2010 |archive-date=27 November 2022 |archive-url=https://web.archive.org/web/20221127050225/http://www.caymanpost.gov.ky/portal/page?_pageid=1327,1736998&_dad=portal&_schema=PORTAL |url-status=dead }}</ref> [[Montserrat]] and the [[British Virgin Islands]].<ref>{{Cite web |url=http://www.caribbeannetnews.com/cgi-script/csArticles/articles/000034/003481.htm |title=British Virgin Islands to get its own postal code |publisher=Caribbeannetnews.com |date=29 September 2006 |access-date=1 September 2010 |url-status=dead |archive-url=https://web.archive.org/web/20091004101335/http://www.caribbeannetnews.com/cgi-script/csArticles/articles/000034/003481.htm |archive-date=4 October 2009}}</ref> Montserrat recently introduced postal codes,<ref>{{cite web|url=http://www.gov.ms/wp-content/uploads/2014/02/Postal-Code-Guide-pamphlet.pdf|title=A Quick Guide to Using Postcode in Your Mail |website=Gov.ms|access-date=8 October 2017}}</ref> and a system has been under consideration in [[Gibraltar]]<ref name=gibralta>{{cite news |url=http://www.gibraltarnewsonline.com/2006/06/30/government-set-to-introduce-post-codes/ |archive-url=https://web.archive.org/web/20061020003717/http://www.gibraltarnewsonline.com/2006/06/30/government-set-to-introduce-post-codes/ |archive-date=20 October 2006 |title=Government set to introduce post codes |work=Gibraltar News |url-status=usurped |date=30 June 2006}}</ref> with the code GX11 1AA being introduced as the generic postcode for the territory in the interim.<ref name="gx111aa">{{cite web |url=https://www.upu.int/UPU/media/upu/PostalEntitiesFiles/addressingUnit/gibEn.pdf |archive-url=https://web.archive.org/web/20210506211550/https://www.upu.int/UPU/media/upu/PostalEntitiesFiles/addressingUnit/gibEn.pdf |archive-date=2021-05-06 |url-status=live |title=Gibraltar |website=Universal Postal Union |access-date=8 October 2017}}</ref><ref>{{cite news |url=http://www.gibraltarpanorama.gi/163602 |title=No Postcode Envy |date=5 April 2019 |first=Ken |last=Westmoreland |work=Gibraltar Panorama}}</ref>
The separate postal code systems for those territories are shown below:
{| class="wikitable"
|-
! Postcode !! Location
|-
| AI-2640 || [[Anguilla]]<ref name=anguillian>{{cite web |title=Anguilla Has A Postal Code, AI-2640 |archive-url=https://web.archive.org/web/20100514113153/http://www.festival.ai/article/view/5274 |archive-date=14 May 2010 |work=The Anguillian |date=12 October 2007 |url=http://www.festival.ai/article/view/5274}}</ref>
|-
| KY''n-nnnn'' ([http://www.caymanpost.gov.ky/portal/page/portal/poshome/posnpimages/POSTCODE%20FINDER%20COLOUR.pdf List] {{Webarchive|url=https://web.archive.org/web/20170407085851/http://www.caymanpost.gov.ky/portal/page/portal/poshome/posnpimages/POSTCODE%20FINDER%20COLOUR.pdf |date=7 April 2017 }}) || [[Cayman Islands]]
|-
| MSR-''nnnn'' ([http://www.gov.ms/wp-content/uploads/2014/02/Postal-Code-Guide-pamphlet.pdf List]) || [[Montserrat]]
|-
| VG-''nnnn'' ([http://www.bvi.gov.vg/content/what-are-postcodes-addresses-british-virgin-islands List]) || [[British Virgin Islands]]
|-
| ''aa nn'' or ''aa aa'' [https://www.bermudayp.com/article/view/1963/2018/5/bermuda-postal-codes List] || [[Bermuda]]
|}
The British Sovereign Base Areas of [[Akrotiri and Dhekelia]] in Cyprus use [[postal codes in Cyprus|Cypriot postal codes]] for civilian use. The British military use BFPO addresses.
==={{anchor|British Forces}} British Forces Post Office (BFPO)===
<!-- This Anchor tag serves to provide a permanent target for incoming section links. Please do not move it out of the section heading, even though it disrupts edit summary generation (you can manually fix the edit summary before saving your changes). Please do not modify it, even if you modify the section title. See [[Template:Anchor]] for details. (This text: [[Template:Anchor comment]]) -->
The [[British Forces Post Office]] (BFPO) provides a postal service to HM Forces separate from that provided by Royal Mail in the United Kingdom, with BFPO addresses used for the delivery of mail in the UK and around the world. BFPO codes such as "BFPO 801" serve the same function as postal codes for civilian addresses, with the last line of the address consisting of "BFPO" followed a space and a number of 1 to 4 digits.
For consistency with the format of other UK addresses, in 2012 BFPO and Royal Mail jointly introduced an optional alternative postcode format for BFPO addresses, using the new non-geographic postcode area "BF" and the notional [[post town]] "BFPO". Each BFPO number is assigned to a postcode in the standard UK format, beginning "BF1". Inward codes are assigned: 0 – Germany, 1 – UK, 2 – Rest of Europe, 3 – Rest of World, 4 – Ships and Naval Parties, 5 – Rest of World, Operations and Exercises, 6 – Rest of World, Operations and Exercises.<ref name="santa" /> The database was released commercially in March 2012 as part of the Royal Mail [[Postcode Address File|Postal Address File]] (PAF).<ref>{{Cite web|url=http://www.raf.mod.uk/community/news/archive/a-better-deal-for-overseas-personnel-23042012|title=A better deal for overseas personnel|publisher=Royal Air Force|date=23 April 2012|access-date=30 July 2012}}</ref><ref>{{Cite web|url=http://www.mod.uk/NR/rdonlyres/D4C88C78-EB65-405E-ACBD-C107A28D5981/0/bfpo__indicator_list.pdf |archive-url=https://web.archive.org/web/20120524131704/http://www.mod.uk/NR/rdonlyres/D4C88C78-EB65-405E-ACBD-C107A28D5981/0/bfpo__indicator_list.pdf |archive-date=2012-05-24 |url-status=live|title=BFPO Indicator List|publisher=Ministry of Defence|date=April 2012|access-date=30 July 2012}}</ref> A postcode is not required if the traditional "BFPO nnnn" format is used.
===Non-geographic postcodes===
Overview: Almost all postcodes areas and almost all postcodes apply to a geographic area (buildings or streets) but some (areas, districts and specific postcodes) are used only for sorting/routing and thus cannot be used for identifying ___location, estimating distance or route finding in SatNav systems.<ref name="non_geo">{{Cite FTP |url=ftp://ftp.royalmail.com/Downloads/public/ctf/rm/07mar_Current_Non_Geo.pdf |server=FTP server |url-status=dead |title=07mar_Current_Non_Geo.xls|access-date=1 September 2010 }}</ref> They are commonly termed “non-geographic” postcodes in the sense that they refer not to physical addresses but to specific recipients (who have made arrangements for the delivery of incoming mail).
"Non-geographic" postcodes are used for various purposes, many of which were introduced after, or have significantly evolved since, the introduction of the current post code system, including: Admail, "bulk mail" or large volumes (government and business), centralised scanning of inward mail, competitions, parcel returns, [[direct marketing]] and [[PO box]]es. They are also referred to as "business service indicator addresses".
Some may be defunct or transferred e.g. Jobcentre typically had the aa98 or aa99 district in each postcode area but each office is now allocated a specific post code in the WV98 and WV99 districts, with the mail digitally scanned after delivery). A limited number are shared with geographic postcode districts, but are differentiated by their post town.
These postcodes cover -
* Post boxes: e.g. in the Brighton BN postcode area, BN50-BN52 are allocated to PO Boxes in Brighton, Rottingdean and Hove.
* Post boxes in London: London postcode districts ending in -P, such as SE1P, are usually allocated to PO Boxes (inconsistently, other letters are also used, and -P has been allocated to geographic addresses, such as SW1P).
* Postcode district: many geographic postcode areas also contain postcode districts that are "non-geographic" and are allocated to specific recipients which are government departments or commercial businesses (e.g. WV98 and WV99 for the Department of Work and Pensions correspondence.[https://www.whatdotheyknow.com/request/non_geographic_bx_postcodesbsi_a]). These are referred to as Large User (LU) in the Postcode Address File.
* Postcode area BF: BF is entirely non-geographic (see above).
* Postcode area BX: BX is entirely non-geographic, with all its codes independent of the ___location of the recipient.
* Postcode area XX: the XX postcode area is non-geographic and is allocated for parcel returns of large volume online retailers (and was used for medical sample testing during the COVID pandemic).
Numbering rules: There appear to be no binding rules publicly available for numbering of non-geographic districts, and therefore can be numbered anywhere in the range 0 to 99, but many such districts are allocated a number higher than the currently existing postcode districts and often in the range 90-99 (several government departments use the '''AA98''' or '''AA99''' district in a number of postcode areas) - retrieved from PAF file, [[List of postcode areas in the United Kingdom]]. This is possible in most postcode areas as only a very small number have allocated geographic districts in that number range (B90-B98, BT92-BT94 and M90 seem to be the only geographic districts in this range). However, there are many non-geographic districts numbered outside this range (e.g. American Express has the postcode district BN88; in Glasgow G58 is allocated to National Savings, as part of a mnemonic postcode G58 1SB, though it is located in G43 postcode district).
Significant addressees: Some postcodes in the "non-geographic" range 90–99 are in fact geographic, but specific to the institution or entity and not part of the surrounding numbering sequence (and thus quite different from the neighbouring properties): for example, '''EH99''' 1SP can be used with GPS mapping to locate and navigate to the Scottish Parliament (which is directly opposite the Palace of Holyroodhouse, EH8 8DX, and across the road from 7/4 Canongate, EH8 8BX).
Postcode ending nHQ: The letters '''HQ''' for the last two letters may also mean it is most likely a non-geographic postcode or that Royal Mail holds the mail where a redirection, bulk mail delivery or open and scan to email service is available.
[[Girobank]]'s headquarters in [[Bootle]] used the non-geographic postcode '''GIR''' 0AA.
There is also a special postcode for [[letters to Santa|letters to Santa/Father Christmas]], '''XM4''' 5HQ.<ref name="santa">{{Cite web |website=gov.uk |date=12 May 2024 |title=Find a BFPO address |url=https://www.gov.uk/bfpo/find-a-bfpo-number |access-date=12 May 2024}}</ref>
Publication: Many non-geographic postcodes do not appear on Royal Mail's own online postcode finder tool or their Click and Drop online postage printing tool, which can add to confusion when responding to organisations that use such addresses. Likewise, delivery services or couriers other than Royal Mail may not be able to deliver to such non-physical addresses. The UK government provides for couriers alternative geographic addresses to their BX addresses.[https://www.gov.uk/government/organisations/hm-revenue-customs/contact/couriers]
Extent: Non-geographic postcode districts have been allocated in 63 of the 121 postcode areas (and also in two of three postcode areas of the Crown Dependencies).
{| class="wikitable"
|+
!Postcode Area
!Non-geographic districts
!Notes
|-
|AB
|99
|
|-
|B
|99
|
|-
|BA
|9
|
|-
|BB
|0, 94
|
|-
|BD
|97, 98, 99
|
|-
|BN
|50, 51, 52, 88, 91, 95, 99
|50-52 for PO Boxes
|-
|BS
|0, 98, 99
|
|-
|BT
|58
|
|-
|CA
|95, 99
|
|-
|CF
|30, 91, 95, 99
|
|-
|CH
|25-34, 88, 99
|25-34 for PO Boxes
|-
|CM
|92, 98, 99
|
|-
|CR
|9, 44, 90
|
|-
|CT
|50
|
|-
|CW
|98
|
|-
|DE
|1, 45, 99
|For DE1 and DE45, only sectors 0 and 9 respectively
|-
|DH
|97, 98, 99
|
|-
|DL
|98
|
|-
|DN
|55
|Royal Mail services
|-
|E
|77, 98
|
|-
|EC
|1P, 2P, 3P, 4P, 50
|1P to 4P for PO Boxes
|-
|EH
|77, 91, 95, 99
|
|-
|G
|9, 58, 70, 79, 90
|
|-
|GL
|11
|
|-
|GU
|95
|
|-
|HP
|22
|
|-
|IP
|98
|
|-
|IV
|99
|
|-
|KY
|99
|
|-
|L
|67, 69, 70, 71, 72, 73, 74, 75, 80
|69 for PO Boxes
|-
|LE
|21, 41, 55, 87, 94, 95
|
|-
|LS
|88, 98, 99
|99 for PO Boxes
|-
|M
|60, 61, 99
|
|-
|ME
|99
|
|-
|MK
|77
|
|-
|N
|1P, 81
|1P for PO Boxes
|-
|NE
|82, 83, 85, 88, 92, 98, 99
|99 for PO Boxes
|-
|NG
|70, 80, 90
|
|-
|NN
|99
|
|-
|NR
|18, 19, 26, 99
|NR18 appears to be both geographic and non-geographic
|-
|NW
|1W, 26
|26 for PO Boxes
|-
|OL
|16, 95
|
|-
|PE
|99
|
|-
|PL
|95
|
|-
|PO
|24
|
|-
|PR
|0, 11
|
|-
|RH
|77
|
|-
|S
|49, 94, 95, 96, 97, 98, 99
|
|-
|SA
|48, 72, 80, 99
|
|-
|SE
|1P
|PO Boxes
|-
|SR
|9, 43
|
|-
|SS
|1
|Post town Westcliff - PO Boxes
|-
|SY
|99
|
|-
|TN
|2
|Post town Wadhurst
|-
|TQ
|9
|
|-
|UB
|3, 5, 8, 18
|
|-
|W
|1A
|PO Boxes
|-
|WA
|55, 88
|
|-
|WD
|99
|
|-
|WF
|90
|
|-
|WR
|11, 78, 99
|WR11 post town Broadway
|-
|WV
|1, 98, 99
|WV1 post town Willenhall
|-
|YO
|90
|
|-
|JE
|1, 4, 5
|JE4 for PO Boxes
|-
|IM
|86, 87, 99
|Allocated to large users and PO Boxes
|}
===Special and customised postcodes===
[[Postcodes]] are allocated by Royal Mail's Address Management Unit. In general, they cannot be purchased or specified by the recipient. Royal Mail has sometimes assigned semi-[[mnemonic]] postcodes (sometimes based on the actual geographic postcode district) to high-profile organisations.<ref name="bbceu">{{cite news |url=https://www.bbc.co.uk/news/uk-politics-19046445 |title=Postcode lottery? How EU entered historic Conservative address |first=Gavin |last=Stamp |publisher=[[BBC News]] |date=31 July 2012 |access-date=31 July 2012}}</ref> Royal Mail does offer a limited form of postcode customisation, so to make it unique and personal. A customised Postcode can only be issued in the UK for a brand new development or an organisation that already has a large user Postcode. This form of customisation is limited to the last two characters (letters) of the postcode.
Prominent examples (for both geographic and special case postcodes) are:
{| class="wikitable"<!-- PLEASE ADD ONLY PROMINENT EXAMPLES BELOW. There is a 1 in 400 chance of the last two letters matching ANY pair of initials at random, so do not include an organisation that matches only by coincidence -->
|-
! Postcode !! Organisation<ref name="addresspfinder">See Royal Mail's online [http://www.royalmail.com/postcode-finder Postcode Finder] for full postal addresses.</ref>
|-
| B1 '''1HQ''' || [[HSBC UK]] '''h'''ead'''q'''uarters at '''1''' Centenary Square, Birmingham
|-
| <s>BS98 1'''TL'''</s>|| [[TV Licensing|'''T'''V '''L'''icensing]]<ref>{{Cite web |url=http://www.tvlicensing.co.uk/about/viewcontent.aspx?id=AB7&iqdocumentid=AB7 |title=Making a complaint |publisher=TV Licensing |access-date=31 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120505193922/http://www.tvlicensing.co.uk/about/viewcontent.aspx?id=AB7&iqdocumentid=AB7 |archive-date=5 May 2012}}</ref> (now changed to DL98 1'''TL''')
|-
| BX1 1'''LT''' || [[Lloyds Bank|Lloyds Bank formerly known as '''L'''loyds '''T'''SB Bank]]<ref>{{Cite web |url=http://www.lloydstsb.com/virtual_assistant_faqs.asp |title=Lloyds TSB – Frequently asked questions |publisher=Lloydstsb.com |access-date=31 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120616172152/http://www.lloydstsb.com/virtual_assistant_faqs.asp |archive-date=16 June 2012}}</ref>—BX postcode area is non-geographic
|-
| BX2 1'''LB''' || [[Bank of Scotland]] (part of [[Lloyds Banking Group|'''L'''loyds '''B'''anking Group]])<ref>{{Cite web |url=http://www.bankofscotlandbusiness.co.uk/pdf/Key_Card_terms_and_Conditions.pdf |title=Terms and Conditions – Keycard|publisher=bankofscotlandbusiness.co.uk |date=December 2011 |access-date=31 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121106022939/http://www.bankofscotlandbusiness.co.uk/pdf/Key_Card_terms_and_Conditions.pdf |archive-date=6 November 2012}}</ref>—BX postcode area is non-geographic
|-
| BX3 2'''BB''' || [[Barclays|'''B'''arclays '''B'''ank]]<ref>{{Cite web|url=http://www.lombardmedical.com/pwpcontrol.php?pwpID=5258 |title=Investor and Advisors Contacts |publisher=Lombard Medical |access-date=31 July 2012}}</ref>—BX postcode area is non-geographic
|-
| BX4 '''7SB''' || [[TSB Banking Group|'''TSB''' Bank]]—BX postcode area is non-geographic
|-
| BX5 '''5AT''' || '''[[VAT]]''' Central Unit of [[HM Revenue and Customs]]<ref>{{Cite web |url=http://www.hmrc.gov.uk/vat/managing/returns-accounts/completing-returns.htm |title=How to complete your VAT Return |publisher=HM Revenue and Customs |access-date=31 July 2012}}</ref> ([[Roman numeral]] "''V''AT" = "''5''AT")—BX postcode area is non-geographic
|-
| CF10 1'''BH''' || Lloyds Banking Group (formerly '''B'''lack '''H'''orse Finance)
|-
| CF99 1'''NA''' || [[Senedd]] (formerly '''N'''ational '''A'''ssembly for Wales)
|-
| CO4 '''3SQ'''
|[[University of Essex]] ('''Sq'''uare '''3''')
|-
| CV4 8'''UW''' || [[University of Warwick|'''U'''niversity of '''W'''arwick]]
|-
| CV35 0'''DB''' || [[Aston Martin]] after their sports cars named "'''DB'''"
|-
|'''DA'''1 1'''RT'''
|[[Dartford F.C.]] (nicknamed The '''Dart'''s)
|-
| <s>D'''E99''' '''3GG'''</s> || [[Egg Banking|'''Egg''' Banking]] (decommissioned in February 2018, after the closure of the bank<ref>{{cite web | url=https://www.streetcheck.co.uk/postcode/de993gg |title=Area Information for Riverside Road, Pride Park, Derby, DE99 3GG |access-date=13 February 2024 }}</ref> )
|-
| DE55 4'''SW''' || [[Slimming World|'''S'''limming '''W'''orld]]
|-
| DH98 1'''BT''' || [[BT Group|'''B'''ritish '''T'''elecom]]
|-
| DH99 1'''NS''' || [[National Savings and Investments|'''N'''ational '''S'''avings]] certificates administration
|-
| E14 5'''HQ''' || [[HSBC]] '''h'''ead'''q'''uarters at [[8 Canada Square]], Canary Wharf
|-
| E14 5'''JP''' || [[JP Morgan|'''JP''' Morgan (Bank Street)]]
|-
| E16 1'''XL''' || [[ExCeL London|'''ExCeL''' London]]<ref>{{Cite web |url=http://www.excel-london.co.uk/about-excel/media-centre/media-contacts/ |title=Media Contacts |publisher=ExCel London |access-date=31 July 2012 |archive-url=https://web.archive.org/web/20120731043354/http://www.excel-london.co.uk/about-excel/media-centre/media-contacts |archive-date=31 July 2012 |url-status=dead}}</ref>
|-
| E20 2'''AQ''' || Olympic '''Aq'''uatics Centre
|-
| E20 2'''BB''' || Olympic '''B'''asket'''b'''all Arena
|-
| E20 2'''ST''' || Olympic '''St'''adium
|-
| E20 3'''BS''' || Olympic '''B'''roadca'''s'''t Centre
|-
| E20 3'''EL''' || Olympic V'''el'''odrome
|-
| E20 3'''ET''' || Olympic '''Et'''on Manor Tennis Courts
|-
| E20 3'''HB''' || Olympic '''H'''and'''b'''all Arena (now the [[Copper Box]])
|-
| E20 3'''HY''' || Olympic '''H'''ocke'''y''' Stadium
|-
| E98 1'''SN''' || ''[[The Sun (United Kingdom)|The '''S'''u'''n''']]'' newspaper
|-
| E98 1'''ST''' || ''[[The Sunday Times|The '''S'''unday '''T'''imes]]'' newspaper
|-
| E98 1'''TT''' || ''[[The Times|'''T'''he '''T'''imes]]'' newspaper
|-
| EC2N 2'''DB''' || [[Deutsche Bank|'''D'''eutsche '''B'''ank]]
|-
| EC2Y 8'''HQ''' || [[Linklaters]] '''h'''ead'''q'''uarters at One [[Silk Street, London|Silk Street]]
|-
| EC4Y 0'''HQ''' || Royal Mail Group Ltd '''h'''ead'''q'''uarters
|-
| EC4Y 0'''JP''' || [[JP Morgan|'''JP''' Morgan (Victoria Embankment)]]
|-
| EH12 1'''HQ''' || [[NatWest Group]] '''h'''ead'''q'''uarters
|-
| EH'''99''' 1'''SP''' || [[Scottish Parliament|'''S'''cottish '''P'''arliament]]<ref>{{Cite web |url=http://www.scottish.parliament.uk/help/13593.aspx |title=Contact Us |publisher=Scottish.parliament.uk |access-date=31 July 2012}}</ref> (founded in 19'''99''')
|-
| G'''58''' 1'''SB''' || [[National Savings and Investments|National '''S'''avings '''B'''ank]] (the district number ''58'' also approximates the outline of the initials ''SB'')
|-
| <s>'''GIR 0'''AA</s>|| [[Girobank|'''Giro'''bank]] (now [[Santander Corporate Banking]])
|-
|HA9 0'''WS'''
|'''W'''embley '''S'''tadium
|-
| <s>HP5 '''1WA'''</s>|| [[Inland Waterways Association|'''I'''nland '''W'''aterways '''A'''ssociation]] (decommissioned when the IWA moved office in April 2023<ref>{{cite web | url=https://waterways.org.uk/contact-us | title=Contact Us}}</ref>)
|-
| IV21 '''2LR''' || [[Two Lochs Radio|'''Two''' '''L'''ochs '''R'''adio]]
|-
| L30 4'''GB''' || '''G'''iro'''b'''ank (alternative geographic postcode)
|-
| LS98 1'''FD''' || [[First Direct|'''F'''irst '''D'''irect]] bank
|-
| M50 2'''BH''' || BBC '''B'''ridge '''H'''ouse
|-
| M50 2'''QH''' || BBC '''Q'''uay '''H'''ouse
|-
| N1 9'''GU''' || ''[[The Guardian|The '''Gu'''ardian]]'' newspaper
|-
| N81 1'''ER''' || [[Electoral Reform Services|'''E'''lectoral '''R'''eform Services]]<ref name="non_geo"/><ref>{{London Gazette |issue=58985 |date=20 February 2009 |page=3105 }}</ref>
|-
| NE1 4'''ST''' || [[St James' Park|'''St''' James' Park '''St'''adium]], [[Newcastle United]]
|-
| NG80 1'''EH''' || [[Experian]] '''E'''mbankment '''H'''ouse
|-
| NG80 1'''LH''' || Experian '''L'''ambert '''H'''ouse
|-
| NG80 1'''RH''' || Experian '''R'''iverleen '''H'''ouse
|-
| NG80 1'''TH''' || Experian '''T'''albot '''H'''ouse
|-
| RM11 1'''QT''' || [[Queen's Theatre, Hornchurch|'''Q'''ueen's '''T'''heatre]], Hornchurch
|-
| PH1 2'''SJ''' || [[St Johnstone F.C.|'''S'''t '''J'''ohnstone Football Club]]
|-
|<s>PH1 5'''RB'''</s>
|'''[[Royal Bank of Scotland|R]]'''[[Royal Bank of Scotland|oyal '''B'''ank of Scotland]] Perth Chief Office (now closed)
|-
| S2 4'''SU''' || [[Sheffield United F.C.|'''S'''heffield '''U'''nited Football Club]]
|-
| S6 1'''SW''' || [[Sheffield Wednesday F.C.|'''S'''heffield '''W'''ednesday Football Club]]
|-
| S'''14 7UP''' ||| The [[World Snooker Championships]] at the [[Crucible Theatre]], Sheffield;<ref>{{Cite web |url=http://genome.ch.bbc.co.uk/89c38da818d84670a3e6943f21a43a6d |title=BBC Genome: World Snooker (1989) |date=24 April 1989 |publisher=BBC |access-date=9 September 2015}}</ref> 147 UP refers to a maximum lead (from a [[maximum break]]) in snooker
|-
|S70 1'''GW'''
|The '''G'''lass '''W'''orks - retail and leisure centre in Barnsley town centre
|-
| SA99 || [[Driver and Vehicle Licensing Agency]]—All postcodes starting with SA99 are for the DVLA offices in the [[Morriston]] area of [[Swansea]].<br>The final part of the postcode relates to the specific office or department within the DVLA.
|-
| SE1 '''0NE''' || [[Thomas Bennett (architect)|'''One''' America Street]], the London headquarters of architectural firm TP Bennett
|-
| SE1 8'''UJ''' || [[Union Jack Club|'''U'''nion '''J'''ack Club]]
|-
| SM6 0'''HB''' || [[Homebase|'''H'''ome'''b'''ase Limited]]
|-
| SN38 1'''NW''' || [[Nationwide Building Society|'''N'''ation'''w'''ide Building Society]]
|-
| SR5 1'''SU''' || [[Stadium of Light|Stadium of Light, '''Su'''nderland AFC]]
|-
| SW1A 0AA || [[House of Commons of the United Kingdom|House of Commons]] ([[Palace of Westminster|'''P'''alace of '''W'''estminster]]; see below for House of Lords)
|-
| SW1A 0'''PW''' || [[House of Lords]] ([[Palace of Westminster|'''P'''alace of '''W'''estminster]]; see above for House of Commons)
|-
| SW1A 1AA || [[Buckingham Palace]] ([[Monarchy of the United Kingdom|the Monarch]])
|-
| SW1A 2AA || [[10 Downing Street]] ([[Prime Minister of the United Kingdom|the Prime Minister]])
|-
|SW1A 2AB
|[[11 Downing Street]] ([[Chancellor of the Exchequer]])
|-
| SW1H 0'''TL''' || [[Transport for London|'''T'''ransport for '''L'''ondon]] (Windsor House, 50 Victoria Street)
|-
| SW1P 3'''EU''' || European Commission and European Parliament office ([[European Union|'''E'''uropean '''U'''nion]])
|-
| SW1W 0'''DT''' || ''[[The Daily Telegraph|The '''D'''aily '''T'''elegraph]]'' newspaper
|-
| SW1V 1'''AP''' || [[Apollo Victoria Theatre|'''Ap'''ollo Victoria Theatre]]
|-
| SW1X 1'''SP''' || [[High Commission of Singapore, London|High Commission of '''S'''inga'''p'''ore, London]]
|-
| SW11 7'''US''' || [[Embassy of the United States, London|Embassy of the '''U'''nited '''S'''tates, London]]
|-
| SW19 5'''AE''' || [[All England Lawn Tennis and Croquet Club|'''A'''ll '''E'''ngland Lawn Tennis and Croquet Club]] (Venue of the [[Wimbledon Championships]])
|-
| TW8 9'''GS''' || ''[[GlaxoSmithKline|'''G'''laxo'''S'''mithKline]]''
|-
| W1A 1'''AA''' || [[BBC]] [[Broadcasting House]] ([[W1A (TV series)|independently notable postcode]])
|-
| <s>W1D 4'''FA'''</s> || The former address of [[The Football Association|The '''F'''ootball '''A'''ssociation]] (decommissioned in February 2010 after they moved ___location<ref>{{Cite web |url=https://www.streetcheck.co.uk/postcode/w1d4fa |title=Area Information for London, W1D 4FA |access-date=13 February 2024}}</ref>)
|-
| W1N 4'''DJ''' || [[BBC Radio 1]] ([[Disc jockey|'''d'''isc '''j'''ockey]])
|-
| W1T 1'''FB''' || [[Facebook|'''F'''ace'''b'''ook]]
|}
The postcode printed on Business Reply envelopes (which do not require a stamp) often ends with the letters '''BR'''.
Post codes ending 1AA are usually allocated to post offices (Crown, main and sub-) such as NR3 1AA for Magdalen Street post office in Norwich. Some are defunct following disposal of former Post Office buildings (e.g. EH1 1AA in Edinburgh).
==Operation==
===Sorting===
Postcodes are used to sort letters to their destination either manually, where sorters use labelled frames, or increasingly with letter-coding systems, where machines assist in sorting.<ref name=compcomm1>{{cite book |title=The Post Office Letter Post Service: a report on the letter post service of the Post Office in the Head Post Office areas of Glasgow, Belfast and Cardiff and in the numbered London postal districts |url=http://www.competition-commission.org.uk/rep_pub/reports/1984/fulltext/180c02.pdf |chapter=2: The organisation of the Post Office and its letter post operations |pages=19–20 |year=1984 |publisher=[[Competition Commission]] |archive-url=http://webarchive.nationalarchives.gov.uk/20120119215329/http://www.competition-commission.org.uk/rep_pub/reports/1984/fulltext/180c02.pdf |archive-date=19 January 2012 |url-status=usurped |access-date=28 June 2014}}</ref> A variation of automated sorting uses [[optical character recognition]] (OCR) to read printed postcodes, best suited to mail that uses a standard layout and addressing format.<ref name="clear">{{cite web |url=http://www.royalmail.com/sites/default/files/Guide_for_clear_addressing_August2012.pdf |title=A guide for letter envelope design and clear addressing – How to get it right |date=August 2012 |work=[[Royal Mail]] |access-date=28 June 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141031014230/http://www.royalmail.com/sites/default/files/Guide_for_clear_addressing_August2012.pdf |archive-date=31 October 2014}}</ref>
A long string of "faced" letters (i.e. turned to allow the address to be read) is presented to a keyboard operator at a coding desk, who types the postcodes onto the envelopes in coloured phosphor dots. The associated machine uses the outward codes in these dots to direct bundles of letters into the correct bags for specific delivery offices. With a machine knowledge of the specific addresses handled by each postal walk at each office, the bundles can be further sorted using the dots of the inward sorting code so that each delivery round receives only its own letters.<ref name="Postcodes & Addresses Explained">{{cite web |url=http://www.royalmail.com/delivery/mail-advice/postcodes-addresses-explained |title=Postcodes & Addresses Explained |work=[[Royal Mail]] |archive-url=https://web.archive.org/web/20120716211307/http://www.royalmail.com/delivery/mail-advice/postcodes-addresses-explained |archive-date=16 July 2012 |access-date=28 June 2014}}</ref> This feature depends upon whether it is cost effective to second-sort outward letters, and tends to be used only at main sorting offices where high volumes are handled.<ref name=compcomm>{{cite book|url=http://www.competition-commission.org.uk/rep_pub/reports/1984/fulltext/180c02.pdf/|title=The Post Office Letter Post Service: a report on the letter post service of the Post Office in the Head Post Office areas of Glasgow, Belfast and Cardiff and in the numbered London postal districts|chapter=2: The Organisation of the Post Office and its letter post operations|year=1984|publisher=[[Competition Commission]]|access-date=9 May 2011|pages=19–20|quote=When the mail reaches its destination delivery office, it is sorted into postmen's walks. Each postman then 'sets in' his mail into the order of his walk. Where the posttown is an MLO, the primary and walk sorting processes may be performed by machine if the mail already bears code marks|url-status=usurped|archive-url=https://web.archive.org/web/20110708151410/http://www.competition-commission.org.uk/rep_pub/reports/1984/fulltext/180c02.pdf|archive-date=8 July 2011}}</ref>
When postcodes are incomplete or missing, the operator reads the post town name and inserts a code sufficient for outward sorting to the post town, where others can further direct it. The mail bags of letter bundles are sent by road, air or train, and eventually by road to the delivery office.<ref name=compcomm/> At the delivery office the mail that is handled manually is inward sorted to the postal walk that will deliver it; it is then "set in", i.e. sorted into the walk order that allows the deliverer the most convenient progress in the round.<ref name="Postcodes & Addresses Explained"/><ref name=compcomm/> The latter process is now being automated, as the roll-out of walk sequencing machines continues.<ref>{{cite web |url=http://www.royalmailgroup.com/£120-million-further-investment-royal-mail-modernisation |title=£120 Million Further Investment in Royal Mail Modernisation |date=21 July 2009 |work=[[Royal Mail]] |access-date=28 June 2014 |archive-url=https://web.archive.org/web/20160313135623/http://www.royalmailgroup.com/%c2%a3120-million-further-investment-royal-mail-modernisation |archive-date=13 March 2016 |url-status=dead}}</ref><ref name=improve>{{cite web |url=http://www.royalmail.com/personal/help-and-support/how-are-you-going-to-improve-the-way-you-sort-the-mail |title=Modernisation – Transforming how we sort your mail |work=[[Royal Mail]] |access-date=28 June 2014 |quote=We’re introducing new machines so postmen and women no longer need to sort most of their delivery manually. They will receive mail in the order of their route, so they can get straight out on delivery. |url-status=dead |archive-url=https://web.archive.org/web/20140628165846/http://www.royalmail.com/personal/help-and-support/how-are-you-going-to-improve-the-way-you-sort-the-mail |archive-date=28 June 2014}}</ref>
====Integrated Mail Processors====
Integrated Mail Processors (IMPs) read the postcode on the item and translate it into two phosphorus barcodes representing the inward and outward parts of the postcode, which the machines subsequently print and read to sort the mail to the correct outward postcode. Letters may also be sequentially sorted by a Compact Sequence Sorter (CSS) reading the outward postcode in the order that a walking postman/woman will deliver, door to door. On such items the top phosphorous barcode is the inward part of the code, the bottom is the outward.{{citation needed|date=December 2012}}
IMPs can also read RM4SCC items, as used in Cleanmail, a different format to the above.
====Mailsort and Walksort====
A newer system of five-digit codes called [[Mailsort]] was designed for users who send "a minimum of 4,000 letter-sized items".<ref name=mailsort_faq>{{cite web |url=http://www.royalmailgroup.co.uk/discounts-payment/discounts-letters-uk/walksort/details |archive-url=https://web.archive.org/web/20140222062716/http://www.royalmailgroup.co.uk/discounts-payment/discounts-letters-uk/walksort/details |url-status=dead |archive-date=22 February 2014 |title=Walksort |work=[[Royal Mail]] |access-date=28 June 2014 }}</ref> It encodes the outward part of the postcode in a way that is useful for mail routing, so that a particular range of Mailsort codes goes on a particular plane or lorry. Mailsort users are supplied with a database to allow them to convert from postcodes to Mailsort codes and receive a discount if they deliver mail to the post office split up by Mailsort code. Users providing outgoing mail sorted by postcode receive no such incentive since postcode areas and districts are assigned using permanent mnemonics and do not therefore assist with grouping items together into operationally significant blocks. Walksort{{clarify|date=November 2016}} was discontinued in May 2012.
==Listings and availability==
{{further|List of postcode areas in the United Kingdom|List of postcode districts in the United Kingdom|List of post towns in the United Kingdom}}
There are approximately 1.7 million postcodes in the United Kingdom, the Channel Islands and the Isle of Man.<ref name="pafstats1208">{{Cite web |url=http://www.poweredbypaf.com/wp-content/uploads/2016/06/062016_PAF-Stats.pdf |title=Postcode Address File statistics |work=Royal Mail|date=June 2016 |access-date=21 June 2016 |archive-url=https://web.archive.org/web/20170407184428/https://www.poweredbypaf.com/wp-content/uploads/2016/06/062016_PAF-Stats.pdf |archive-date=7 April 2017 |url-status=dead}}</ref>
Each postcode is divided by a space into two parts. As mentioned above, the first part starts with the [[postcode area]] and ends with the [[postcode district]]. The second part begins with a single digit, which indicates the '''postcode sector''', and ends with the postcode unit.
Postcode areas are also divided into several [[post town]]s, which predate the introduction of postcodes, with the [[London postal district|London]] post town uniquely covering more than one postcode area.
As of June 2016, there are 124 postcode areas, 2,987 postcode districts, 11,192 postcode sectors, and 1,500 post towns.<ref name="pafstats1208" /> {{as of|2021|01}}, 55,540 full postcodes in England and Wales contain only one household.<ref name="ons20210127">{{Cite web |date=27 January 2021 |title=Number of UK postcodes which only have one household |url=https://www.ons.gov.uk/aboutus/transparencyandgovernance/freedomofinformationfoi/numberofukpostcodeswhichonlyhaveonehousehold |access-date=3 March 2023 |website=Office for National Statistics}}</ref> Addresses receiving large volumes of mail are each assigned separate "large user" postcodes. But most postcodes are shared by several neighbouring properties, typically covering about 15 addresses.
===Life-cycle of postcodes===
There are also significant numbers of discontinued (terminated) codes.<ref name="ONS Geography Guide - postcode termination">{{cite web |url=https://geoportal.statistics.gov.uk/datasets/a-beginners-guide-to-uk-geography-2023/about |title=A Beginners Guide to UK Geography (2023) |author=<!--Not stated--> |date=24 August 2023 |website=Open Geography Portal |publisher=Office for National Statistics |access-date=9 December 2023 |quote=Terminated postcodes are postcodes that are no longer used for mail delivery. The most frequent reasons for terminations are postcode reorganisations or the demolition/redevelopment of buildings. Terminated postcodes are occasionally re-used by Royal Mail but usually not before an elapsed period of two years. Terminated postcodes are retained in our postcode directories until or unless they are re-used.}}</ref> Each month some 2,750 postcodes are created and 2,500 terminated.<ref>{{cite web|url=https://www.listmark.net/blog/how-often-do-postcodes-change |title=How often do postcodes change? |last1=Edwards |first1=Alex |date=23 January 2013 |website=Listmark |access-date=28 June 2014 |url-status=dead |archive-url=https://web.archive.org/web/20151016003852/http://www.listmark.net/blog/how-often-do-postcodes-change |archive-date=16 October 2015}}</ref>
{| class="wikitable"
! Component !! Part !! Example !! Live codes<ref name=mailsort_tech>Royal Mail, ''[https://web.archive.org/web/20020215141953/http://www.mailsorttechnical.com/downloads_mailsort.cfm Mailsort Database 2007 Release 1]'', (23 July 2007)</ref>!! Terminated codes<ref name="statistics">National Statistics, ''[http://www.statistics.gov.uk/geography/downloads/NSPDVersionNotes.pdf Postcode Directory Version Notes]'', (2006) {{webarchive|url=https://web.archive.org/web/20090327152039/http://www.statistics.gov.uk/geography/downloads/NSPDVersionNotes.pdf|date=27 March 2009}}, [https://geoportal.statistics.gov.uk/datasets/national-statistics-postcode-lookup-may-2020 ONS]</ref>!! Other codes<br>{{clarify|date=July 2023}} !! Total
|-
| Postcode area || Out code || YO ||align="right"| 124 ||align="right"| 0 ||align="right"| 3 ||align="right"| 127
|-
| Postcode district || Out code || YO31 ||align="right"| 2,984 || align="right" | 103 ||align="right"| 4 ||align="right"| 3,087
|-
| Postcode sector || In code || YO31 1 ||align="right"| 11,197 || align="right" | 1,071 ||align="right"| 4 ||align="right"| 12,272
|-
| Postcode unit || In code || YO31 1EB ||align="right"| 1,767,416<ref name="statistics"/>|| align="right" | 876,312 || align="right" | 4 ||align="right"| 2,643,732
|-
| colspan=3 | [[Postcode Address File|Postcode Addresses]] ||align="right"| Approx. 29,965,962<ref name=mail_paf>{{Cite FTP |url=ftp://ftp.royalmail.com/Downloads/public/ctf/rm/PAF_Digest_Dec_03.pdf|server=FTP server|url-status=dead|title=Royal Mail guide to using the PAF file }}</ref>
| colspan="3"|
|}
===Postcode Address File (PAF)===
The Address Management Unit of [[Royal Mail]] maintains an official database of UK postal addresses and postcodes in its [[Postcode Address File]] (PAF), which is made available under licence for a fee regulated by [[Ofcom]]. The PAF is commercially licensable and is often incorporated in address management software packages. The capabilities of such packages allow most addresses to be constructed solely from the postcode and house number. By including the [[Ordnance Survey|map reference]]s of postcodes in the address database, the postcode can be used to pinpoint a postcode area on a map. PAF is updated daily.
On its website, Royal Mail publishes summary information about major changes to postcode sectors and postal localities (including post towns). Individual postcodes or postal addresses can be found using Royal Mail's [http://www.royalmail.com/find-a-postcode Postcode and Address Finder] website, but this is limited to 50 free searches per user per day.
===
A complete list of all current Great Britain postcodes, known as Code-Point Open, has been made available online (since 1 April 2010) by Ordnance Survey. Under the government's [[OS OpenData]] initiative, it is available for re-use without charge under an attribution-only licence. The Code-Point Open list includes median coordinates for each postcode but excludes postcodes in Northern Ireland and the [[Crown dependencies]]. Unlike the PAF products provided by Royal Mail, the Code-Point Open list does not include postal address text.
===ONS Postcode Directory and National Statistics Postcode Lookup===
The [[Office for National Statistics]] also produces postcode directories, under similar licence terms to the OS product. Both the ONSPD and NSPL contain Northern Ireland postcodes, with centroid coordinates in the [[Ordnance Survey Ireland|OSI]] grid as opposed to the [[Ordnance Survey National Grid|OSGB grid]], although Northern Ireland postcodes are subject to a more restrictive licence permitting internal business use only.<ref name="ons">{{cite web|url=http://www.ons.gov.uk/methodology/geography/licences|title=Licences|website=Office for National Statistics|access-date=31 July 2017}}</ref> Postcodes for the Crown Dependencies are also included, without co-ordinates. A further difference is that non-current postcodes and dates of introduction and withdrawal of postcodes are included.
==Changing postcodes==
There are several groups, mostly on the fringes of major population centres, who are affected in one way or another by the associations of their postcode. There is a movement in the [[Royal Borough of Windsor and Maidenhead]] to change the first two characters of their postcodes from {{postcode|SL}} to WM for vanity, so as not to be associated with [[Slough]].<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/england/2668561.stm |title=England | 'Snobs' want to slough off postcode |publisher=BBC News |date=2003-01-17 |accessdate=2010-01-04}}</ref> A businessman in [[Ilford]] wishes to have the postcode district of {{postcode|IG|1}} changed to {{postcode|E|19}} as he claims customers do not realise his business is based in Greater London.<ref>{{cite news|last=Scrivens |first=Louise |url=http://news.bbc.co.uk/1/hi/england/london/4409163.stm |title=England | London | The power of the postcode |publisher=BBC News |date=2005-04-05 |accessdate=2010-01-04}}</ref>{{Importance inline|date=November 2024}}
Some residents of West Heath in {{postcode|SE|2}} asked to have their postcodes changed to that of adjacent [[Bexleyheath]], citing higher insurance premiums as reason to change.<ref>{{cite web |url=http://www.thisislocallondon.co.uk/archive/display.var.334327.0.cracking_the_codes_not_easy.php |title=Cracking The Codes Not Easy (from This Is Local London) |publisher=Thisislocallondon.co.uk |date=2002-03-12 |accessdate=2010-01-04 |url-status=dead |archiveurl=https://web.archive.org/web/20080526111315/http://www.thisislocallondon.co.uk/archive/display.var.334327.0.cracking_the_codes_not_easy.php |archivedate=2008-05-26 }}</ref> Some residents of [[Kingston Vale]] in {{postcode|SW|15}} wish to have their postcodes changed to adjacent [[Kingston upon Thames]] for the same reasons{{Citation needed|date=March 2007}}.
In all these cases [[Royal Mail]] has said that there is "virtually no hope" of changing the postcode, referring to their policy of changing postcodes only to match changes in their operations.<ref>{{cite news|last=Scrivens |first=Louise |url=http://news.bbc.co.uk/1/hi/england/london/4409163.stm |title=UK | England | London | The power of the postcode |publisher=BBC News |date=2005-04-05 |accessdate=2010-01-04}}</ref> Under this policy residents of the [[Wirral Peninsula]] had their postcodes changed from the {{postcode|L}} (Liverpool) to {{postcode|CH}} (Chester) group when a new sorting office was opened.<ref>{{cite web |url=http://archive.thisiswirral.co.uk/1999/09/09/13953.html |title=Postman Pat Gets L Of A Row Off His Chest — This Is Wirral |publisher=Archive.thisiswirral.co.uk |accessdate=2010-01-04 |url-status=dead |archiveurl=https://web.archive.org/web/20070927084419/http://archive.thisiswirral.co.uk/1999/09/09/13953.html |archivedate=2007-09-27 }}</ref>
Some postcode areas straddle [[England]]'s borders with [[Wales]] and [[Scotland]]. Examples of such postcodes include {{postcode|CH|4}}, {{postcode|SY|10}}, {{postcode|NP|16}} and {{postcode|TD|15}}. This has led to [[British Sky Broadcasting]] subscribers receiving the wrong BBC and ITV regions, and newly licensed [[amateur radio|radio amateurs]] being given incorrect [[call sign]]s.
==Other uses==
{{See also|Postcode lottery}}
While postcodes were introduced to expedite the delivery of mail, they are useful tools for other purposes, particularly because codes are very fine-grained and identify just a few addresses. Among these uses are:
* With [[satellite navigation]] systems, to navigate to an address by street number and postcode
* By life insurance companies and pension funds to assess longevity for pricing and reserving<ref name="insurance">[http://www.actuaries.org.uk/__data/assets/pdf_file/0018/103077/sm20080225.pdf Richards, S. J. Applying survival models to pensioner mortality data, British Actuarial Journal] {{webarchive|url=https://web.archive.org/web/20090108162136/http://www.actuaries.org.uk/__data/assets/pdf_file/0018/103077/sm20080225.pdf |date=8 January 2009 }}</ref>
* By other types of insurance companies to assess premiums for motoring/business/domestic policies
* To determine [[catchment area (human geography)|catchment areas]] for school places or [[General practitioner|doctors']] surgeries
*Finding the nearest branch of an organisation to a given address. A computer program uses the postcodes of the target address and the branches to list the closest branches in order of distance as the crow flies (or, if used in conjunction with street-map software, by road distance). This can be used by companies to inform potential customers where to go, by [[jobcentre]]s to find jobs for job-seekers, to alert people of [[town planning]] applications in their area, and a great many other applications.<ref name="planning" />
The phrase "[[postcode lottery]]" refers to the variation in the availability of services by region, though not always because of postcodes.
For these and related reasons, postcodes in some areas have become indicators of social status. Some residents have campaigned to change their postcode to associate themselves with a more desirable area,<ref>[https://www.bbc.co.uk/news/magazine-26367320 The march of the postcode battlers], BBC News Magazine, 4 March 2014</ref> to disassociate with a poorer area,<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/england/2668561.stm |title='Snobs' want to slough off postcode |publisher=BBC News |date=17 January 2003 |access-date=4 January 2010}}</ref> to reduce insurance premiums or to be associated with an area with a lower [[cost of living]].<ref>{{cite web |url=http://www.thisislocallondon.co.uk/archive/display.var.334327.0.cracking_the_codes_not_easy.php |title=Cracking The Codes Not Easy |work=This Is Local London |date=12 March 2002 |access-date=4 January 2010 |url-status=dead |archive-url=https://web.archive.org/web/20080526111315/http://www.thisislocallondon.co.uk/archive/display.var.334327.0.cracking_the_codes_not_easy.php |archive-date=26 May 2008}}</ref> In all these cases [[Royal Mail]] has said that there is "virtually no hope" of changing the postcode, referring to their policy of changing postcodes only to match changes in their operations.<ref>{{cite news|last=Scrivens |first=Louise |url=http://news.bbc.co.uk/1/hi/england/london/4409163.stm |title=UK | England | London | The power of the postcode |publisher=BBC News |date=5 April 2005 |access-date=4 January 2010}}</ref>
Postcode areas rarely align with local government boundaries. The phenomenon whereby postcodes overlap administrative boundaries is known as 'straddling'.<ref name="ONS Geography Guide">{{cite web |url=https://geoportal.statistics.gov.uk/datasets/a-beginners-guide-to-uk-geography-2023/about |title=A Beginners Guide to UK Geography (2023) |author=<!--Not stated--> |date=24 August 2023 |website=Open Geography Portal |publisher=Office for National Statistics |access-date=9 December 2023 |quote=Straddling refers to the phenomenon of postcodes overlapping administrative (or other geographic) boundaries. This is because postcodes are defined for mail delivery only and take no account of other geographies. However, postcodes are frequently used for referencing data so straddling can create problems when we want to relate postcode-referenced data to higher geographies (for example electoral wards).}}</ref> Some postcodes straddle [[England]]'s borders with [[Wales]] and [[Scotland]], such as CH and TD. This has led to [[British Sky Broadcasting]] subscribers receiving the wrong BBC and ITV regions, and newly licensed [[radio amateurs]] being given incorrect [[call signs]].
{{Postcode areas in the United Kingdom}}
==
*[[List of postcode areas in the United Kingdom]]
*[[List of postal codes]] (around the world)
*[[ACORN (geodemography)|ACORN]]
*[[Address Point]]
*[[
*[[RM4SCC]]—a machine-readable barcode version of the postcode and delivery point suffix
*[[Postcode Address File]]
*[[Unique Property Reference Number]]
==References==
{{Reflist}}
{{UK postal system}}
{{Europe in topic|Postal codes in|UK_only=yes}}
{{DEFAULTSORT:Postcodes in the United Kingdom}}
[[Category:Postcodes in the United Kingdom| ]]
[[Category:Postal codes by country|United Kingdom]]
[[Category:1959 introductions]]
[[Category:Postal history of the United Kingdom]]
[[Category:Postal addresses by country|United Kingdom]]
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