Postcodes in the United Kingdom

Map of postcode areas in the United Kingdom and Crown dependencies, with links to each postcode area

Postal codesused in the United Kingdom,British Overseas TerritoriesandCrown dependenciesare known aspostcodes(originally, postal codes).They areAlpha numericand were adopted nationally between 11 October 1959 and 1974, having been devised by theGeneral Post Office(Royal Mail). The system uses Alpha numeric codes to designate geographic areas. A full postcode, also known as a "postcode unit," identifies a group of addresses or a major delivery point. It consists of an outward code and inward code. The outward code indicates the area and district, while the inward code specifies the sector and delivery point, typically encompassing about 15 addresses.

Postcode areas are generally named after major towns or cities, such as B for Birmingham, although some are named after smaller towns or geographical features. London has eight postcode areas (N, E, EC, SE, SW, W, WC, and NW) instead of a single area, and Northern Ireland uses the BT area code for Belfast. The system aids in sorting mail and is used in various applications. They 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 initial postcode system evolved from named postal districts introduced in London and other large cities from 1857. London was divided into numbered subdivisions in 1917, which extended to other cities by 1934. Each postcode area contains multiple post towns and districts. For example, the GU postcode area covers a significant part of southern England, with Guildford as a major town, and Woking as another post town within the GU22 district.

Overview

Structure

A full postcode is known as a "postcode unit" and designates an area with several addresses or a single major delivery point.The structure of a postcode is two Alpha numeric codes that show, first, the name post town and, second, a small group of addresses in that post town. The first Alpha numeric 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 15 addresses, but sometimes more). 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 Sutton and Morden). A small number are geographic in nature – such as HS for the Outer Hebrides, FY for Fylde (the region around Blackpool) and ME for the Medway conurbation, with Rochester as its main post town. In the case of London (a Post Town), there is not a single "London" postcode area; 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 Belfast). Postcodes generally do not align with historical county or local authority boundaries, and can also cross national boundaries (e.g. CH and TD postcode areas).

Postcode districts and numbering

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.

Each postcode area contains a number of post towns and postcode districts. Example: a sizeable part of southern England is covered by the GU postcode area, named after the town of Guildford. Guildford itself consists of postal districts GU1 and GU2. Nearby Woking, a major commuter town—10 km away—is a post town within the postcode district GU22.

As a general rule, the central part of the town/city the postcode area is named after will have the number 1 e.g. B1 (Birmingham) – but there a limited number of postcode areas that start 0 or 10, e.g. SL0 and AB10. Large post towns are generally numbered from the centre outward such that outlying parts have higher numbered districts. In most post towns, the postcode "aa1 1AA" was allocated to the crown or principal post office. These are increasingly defunct, as post offices have closed or moved.

Alternatively, but less commonly, post towns and postcode districts within the area may be numbered according to: geographical direction (e.g. the Outer Hebrides area HS, the districts are numbered from north to south); Alpha betical order of district sub-offices (particularly in London (e.g. E2 is Bethnal Green, E3 is Bow, E4 is Chingford etc.); and 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). Accordingly, the centrality of a postcode district within a postcode area cannot be reliably inferred from the postcode alone (e.g. SE1 covers a large part of Central London south of the Thames whereas SE2 covers Abbey Wood at the far eastern end of the Elizabeth Line). Seepostcode area.

Numbering of postcode districts is normally consecutive, but this is not universal. Non-consecutive numbering arises when districts are numbered for geographical and/or clustering reasons (e.g. PH postcode area's highest numbered district is PH50 but, within the range of PH1-PH50, the numbers PH27-PH29 and PH45-PH48 are not allocated, so as to maintain a distinct geographical link for each group of allocated numbers).

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 inroute planning softwareand as the lowest level of aggregation incensusenumeration. 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 thePostcode Address Filedatabase.

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.

History

Earlier postal districts

London

Main article:London postal district

The London post town covers 40% ofGreater 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 Alpha betically 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

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.

In 1917,Dublin—then still part of the United Kingdom—was divided intonumbered postal districts.These continue in use in a modified form byAn Post,the postal service of theRepublic 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).

In January 1932 the Postmaster General approved the designation of some predominantly urban areas into numbered districts.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.

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, andelection agentsfor candidates in the upcominggeneral electionwere 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.

The ten areas were:

• Birmingham
• Brighton/Hove
• Bristol
• Edinburgh
• Glasgow
• Leeds/Bradford
• Liverpool
• Manchester/Salford
• Newcastle upon Tyne
• Sheffield

For example,ToxtethwasLiverpool 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 asGreat Barr, Birmingham 22orBirmingham 22a,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.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.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 Alpha numeric code with three letters designating the geographical area and three numbers to identify the individual address.On 28 JulyErnest Marples,thePostmaster General,announced thatNorwichhad 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.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).

In October 1965,Tony Bennas Postmaster Generalannounced that postal coding was to be extended to the rest of the country in the next few years.

On 1 May 1967 postcodes were introduced inCroydon.The many postcodes for central Croydon began with "CRO", while those of the surroundingpost townswith 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 inAberdeen,Belfast,Brighton,Bristol,Bromley,Cardiff,Coventry,Manchester,Newcastle upon Tyne,Newport,Reading,Sheffield,Southamptonand theWestern districtof London.By 1967, codes had been introduced to Aberdeen, Southampton, Brighton andDerby.In 1970, codes were introduced to the London Western andNorth Westernpostal districts.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 ofsorting offices.

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, theMinister of Statefor 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.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.

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.

Girobank's GIR 0AA was the last domestic postcode with a fully Alpha betical 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.

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 £4,000 per year.Following a campaign and a government consultation in 2009,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 Licenceas part ofOS OpenData).

Postcodes linked to a variety of UK geographies

TheOffice 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 Alpha numeric, and are variable in length: ranging from six to eight characters (including a space). Each postcode is divided into two parts separated by a single space: theoutward codeand theinward coderespectively. Theoutward codeincludes thepostcode areaand thepostcode district,respectively. Theinward codeincludes thepostcode sectorand thepostcode unitrespectively. Examples of postcodes are "SW1W 0NY", "PO16 7GZ", "GU16 7HF", and "L1 8JQ".

POSTCODE
Outward code		Inward code
Area	District	Sector	Unit
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.

Postcode area

Thepostcode areais part of the outward code. The postcode area is either one or two characters long and is Alpha betical, with there being 121 such areas. Examples of postcode areas are "L" forLiverpool,"RH" forRedhilland "EH" forEdinburgh.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 ofNorthern Ireland.

Postcode district

Thepostcode districtis 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".

Postcode sector

The postcode sector is made up of a single digit (the first character of the inward code).

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 instanceDriver 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, whereAsignifies a letter and9a digit:

Format	Coverage	Example
AA9A 9AA	WC postcode area; EC1–EC4, NW1W, SE1P, SW1	EC1A 1BB
A9A 9AA	E1, N1, W1	W1A 0AX
A9 9AA	B, E, G, L, M, N, S, W	M1 1AE
A99 9AA		B33 8TH
AA9 9AA	All other postcodes	CR2 6XH
AA99 9AA		DN55 1PT

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
• 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 lettersQ,VandXare not used in the first position.
• The lettersI,JandZare not used in the second position.
• The only letters to appear in the third position areA,B, C, D, E, F, G, H, J, K, P, S, T, UandWwhen the structure starts with A9A.
• The only letters to appear in the fourth position areA, B, E, H, M, N, P, R, V, W, XandYwhen the structure starts with AA9A.
• The final two letters do not useC, I, K, M, OorV,so as not to resemble digits or each other when hand-written.
• Postcode sectors 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).

A postcode can be validated against a table of all 1.7 million postcodes inCode-Point Open.The full delivery address including postcode can be validated against theRoyal MailPostcode Address File(PAF), which lists 29 million valid delivery addresses,constituting most (but not all) addresses in the UK.

The followingregular expressioncan be used for the purpose of validation:

^[A-Z]{1,2}[0-9][A-Z0-9]??[0-9][A-Z]{2}$

The following regular expression can be used for the purpose of validation and includes postcode formats fromSpecial Cases:

^(([A-Z]{1,2}[0-9][A-Z0-9]?|ASCN|STHL|TDCU|BBND|[BFS]IQQ|PCRN|TKCA)?[0-9][A-Z]{2}|BFPO?[0-9]{1,4}|(KY[0-9]|MSR|VG|AI)[ -]?[0-9]{4}|[A-Z]{2}?[0-9]{2}|GE?CX|GIR?0A{2}|SAN?TA1)$

Post towns

All or part of one or more postcode districts are grouped intopost towns.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

Crown dependencies

TheChannel Islandsand theIsle of Manestablished their own postal administrations separate from the UK in 1969. Despite this, they adopted the UK-format postcodes in 1993–94:GuernseyusingGY,the Isle of Man usingIM,andJerseyusingJE.

The independent jurisdiction ofSarkwas assigned a unique postcode district GY10 in 2011 to differentiate it fromAlderney.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]".

British Overseas Territories

Some of theBritish Overseas Territorieshave postcodes that broadly follow the format of the UK postcode system or, in Gibralter's case, adopts the UK format:

Postcode	Location
ASCN 1ZZ	Ascension Island
BBND 1ZZ	British Indian Ocean Territory
BIQQ 1ZZ	British Antarctic Territory
FIQQ 1ZZ	Falkland Islands
GX11 1AA	Gibraltar
PCRN 1ZZ	Pitcairn Islands
SIQQ 1ZZ	South Georgia and the South Sandwich Islands
STHL 1ZZ	Saint Helena
TDCU 1ZZ	Tristan da Cunha
TKCA 1ZZ	Turks and Caicos Islands

These were introduced because mail was often sent to the wrong place, e.g., to St Helena instead ofSt Helens, MerseysideorSt Helens, Isle of Wight.and toEdinburghinstead of Edinburgh,Tristan da Cunha,and many online companies would not accept addresses without a postcode.Mail from the UK continues to be treated as international, not inland, and sufficient postage must be used.

Bermudahas developed itsown postcode system,with unique postcodes for street and PO Box addresses,as have theCayman Islands,Montserratand theBritish Virgin Islands.Montserrat recently introduced postal codes,and a system has been under consideration inGibraltarwith the code GX11 1AA being introduced as the generic postcode for the territory in the interim.

The separate postal code systems for those territories are shown below:

Postcode	Location
AI-2640	Anguilla
KYn-nnnn(List)	Cayman Islands
MSR-nnnn(List)	Montserrat
VG-nnnn(List)	British Virgin Islands
aa nnoraa aaList	Bermuda

The British Sovereign Base Areas ofAkrotiri and Dhekeliain Cyprus useCypriot postal codesfor civilian use. The British military use BFPO addresses.

British Forces Post Office (BFPO)

TheBritish 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 notionalpost 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.The database was released commercially in March 2012 as part of the Royal MailPostal Address File(PAF).A postcode is not required if the traditional "BFPO nnnn" format is used.

Non-geographic codes

Most postcodes apply to a geographic area but some are used only for routing and cannot be used for navigation or estimating distances.They are often used fordirect marketingandPO boxes(e.g. in the Brighton BN postcode area, BN50-BN52 are allocated to PO Boxes in Brighton, Rottingdean and Hove). Non-geographic postcode area BX (possibly for "POBox"?) is entirely non-geographic, with all its codes independent of the location of the recipient. They are also referred to as" business service indicator addresses ", which are used for centralised scanning of inward mail.[1]Similarly, the XX postcode area is allocated for parcel returns of large volume retailers (and for medical sample testing during the COVID pandemic).

Some geographic postcode sectors or districts are set aside solely for non-geographic postcodes (e.g. BS98, BT58, EC50, IM99, JE4, M60, N1P, NE99, SA99, SW9 and WV98). Though there are no binding rules, the first two numbers in the range 91 to 95 are often allocated to businesses and in the range 96 to 99 to Government departments. However, there are many exceptions to this (e.g. American Express has the postcode area 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; and in Glasgow G70 is allocated to HMRC which is located in G67).

The letters HQ for the last two letters may also mean it is most likely a non-graphical 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 inBootleused the non-geographic postcode GIR 0AA. There is also a special postcode forletters to Santa/Father Christmas,XM4 5HQ.

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 alternative geographic addresses to BX addresses for couriers.[2]

Special postcodes

Postcodesare allocated by Royal Mail's Address Management Unit and cannot be purchased or specified by the recipient. However, Royal Mail sometimes assigns semi-mnemonicpostcodes (sometimes based on the actual geographic postcode district) to high-profile organisations.

Prominent examples are:

Postcode	Organisation
B11HQ	HSBC UKheadquarters at1Centenary Square, Birmingham
BS98 1TL	TVLicensing(Now changed to DL98 1TL)
BX1 1LT	Lloyds Bank formerly known asLloydsTSB Bank—non-geographic address
BX2 1LB	Bank of Scotland(part ofLloydsBanking Group)—non-geographic address
BX3 2BB	BarclaysBank—non-geographic address
BX47SB	TSBBank
BX55AT	VATCentral Unit ofHM Revenue and Customs(Roman numeral"VAT "="5AT ")—non-geographic address
CF10 1BH	Lloyds Banking Group (formerlyBlackHorse Finance)
CF99 1NA	Senedd(formerlyNationalAssembly for Wales)
CO43SQ	University of Essex(Square3)
CV4 8UW	University ofWarwick
CV35 0DB	Aston Martinafter their sports cars named "DB"
DA1 1RT	Dartford F.C.(nicknamed TheDarts)
DE993GG	EggBanking(decommissioned in February 2018, after the closure of the bank)
DE55 4SW	SlimmingWorld
DH98 1BT	BritishTelecom
DH99 1NS	NationalSavingscertificates administration
E14 5HQ	HSBCheadquarters at8 Canada Square,Canary Wharf
E14 5JP	JPMorgan (Bank Street)
E16 1XL	ExCeLLondon
E20 2AQ	OlympicAquatics Centre
E20 2BB	OlympicBasketball Arena
E20 2ST	OlympicStadium
E20 3BS	OlympicBroadcast Centre
E20 3EL	Olympic Velodrome
E20 3ET	OlympicEton Manor Tennis Courts
E20 3HB	OlympicHandball Arena (now theCopper Box)
E20 3HY	OlympicHockeyStadium
E98 1SN	TheSunnewspaper
E98 1ST	TheSundayTimesnewspaper
E98 1TT	TheTimesnewspaper
EC2N 2DB	DeutscheBank
EC2Y 8HQ	Linklatersheadquarters at OneSilk Street
EC4Y 0HQ	Royal Mail Group Ltdheadquarters
EC4Y 0JP	JPMorgan (Victoria Embankment)
EH12 1HQ	NatWest Groupheadquarters
EH991SP	ScottishParliament(founded in 1999)
G581SB	NationalSavingsBank(the district number58also approximates the outline of the initialsSB)
GIR 0AA	Girobank(nowSantander Corporate Banking)
HA9 0WS	WembleyStadium
HP51WA	InlandWaterwaysAssociation(decommissioned when the IWA moved office in April 2023)
IV212LR	TwoLochsRadio
L30 4GB	Girobank (alternative geographic postcode)
LS98 1FD	FirstDirectbank
M50 2BH	BBCBridgeHouse
M50 2QH	BBCQuayHouse
N1 9GU	TheGuardiannewspaper
N81 1ER	ElectoralReform Services
NE1 4ST	StJames' ParkStadium,Newcastle United
NG80 1EH	ExperianEmbankmentHouse
NG80 1LH	ExperianLambertHouse
NG80 1RH	ExperianRiverleenHouse
NG80 1TH	ExperianTalbotHouse
PH1 5RB	RoyalBank of ScotlandPerth Chief Office
RM11 1QT	Queen'sTheatre,Hornchurch
PH1 2SJ	StJohnstone Football Club
S2 4SU	SheffieldUnited Football Club
S6 1SW	SheffieldWednesday Football Club
S14 7UP	TheWorld Snooker Championshipsat theCrucible Theatre,Sheffield;147 UP refers to a maximum lead (from amaximum break) in snooker
S70 1GW	TheGlassWorks - 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 theMorristonarea ofSwansea,the final part of the postcode relates to the specific office or department within the DVLA
SE10NE	OneAmerica Street,the London headquarters of architectural firm TP Bennett
SE1 8UJ	UnionJack Club
SM6 0HB	Homebase Limited
SN38 1NW	Nationwide Building Society
SR5 1SU	Stadium of Light,Sunderland AFC
SW1A 0AA	House of Commons(Palace ofWestminster;see below for House of Lords)
SW1A 0PW	House of Lords(Palace ofWestminster;see above for House of Commons)
SW1A 1AA	Buckingham Palace(the Monarch)
SW1A 2AA	10 Downing Street(the Prime Minister)
SW1A 2AB	11 Downing Street(Chancellor of the Exchequer)
SW1H 0TL	Transport forLondon(Windsor House, 50 Victoria Street)
SW1P 3EU	European Commission and European Parliament office (EuropeanUnion)
SW1W 0DT	TheDailyTelegraphnewspaper
SW1V 1AP	Apollo Victoria Theatre
SW11 7US	Embassy of theUnitedStates, London
SW19 5AE	AllEngland Lawn Tennis and Croquet Club(Venue of theWimbledon Championships)
TW8 9GS	GlaxoSmithKline
W1A 1AA	BBCBroadcasting House(independently notable postcode)
W1D 4FA	The former address ofTheFootballAssociation(decommissioned in February 2010 after they moved location)
W1N 4DJ	BBC Radio 1(discjockey)
W1T 1FB	Facebook

The postcode printed on Business Reply envelopes (which do not require a stamp) often ends with the lettersBR.

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.A variation of automated sorting usesoptical character recognition(OCR) to read printed postcodes, best suited to mail that uses a standard layout and addressing format.

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.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.

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.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.The latter process is now being automated, as the roll-out of walk sequencing machines continues.

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.

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 calledMailsortwas designed for users who send "a minimum of 4,000 letter-sized items".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. Walksortwas discontinued in May 2012.

Listings and availability

Further information:List of postcode areas in the United Kingdom,List of postcode districts in the United Kingdom,andList 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.

Each postcode is divided by a space into two parts. As mentioned above, the first part starts with thepostcode areaand ends with thepostcode district.The second part begins with a single digit, which indicates thepostcode sector,and ends with the postcode unit.

Postcode areas are also divided into severalpost towns,which predate the introduction of postcodes, with theLondonpost 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.As of January 2021,55,540 full postcodes in England and Wales contain only one household.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. Each month some 2,750 postcodes are created and 2,500 terminated.

Component	Part	Example	Live codes	Terminated codes	Other codes	Total
Postcode area	Out code	YO	124	0	3	127
Postcode district	Out code	YO31	2,984	103	4	3,087
Postcode sector	In code	YO31 1	11,197	1,071	4	12,272
Postcode unit	In code	YO31 1EB	1,767,416	876,312	4	2,643,732
Postcode Addresses			Approx. 29,965,962

Postcode Address File (PAF)

The Address Management Unit ofRoyal Mailmaintains an official database of UK postal addresses and postcodes in itsPostcode Address File(PAF), which is made available under licence for a fee regulated byOfcom.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 themap referencesof 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'sPostcode and Address Finderwebsite, but this is limited to 50 free searches per user per day.

Code-Point Open

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'sOS OpenDatainitiative, 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 theCrown 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

TheOffice for National Statisticsalso produces postcode directories, under similar licence terms to the OS product. Both the ONSPD and NSPL contain Northern Ireland postcodes, with centroid coordinates in theOSIgrid as opposed to theOSGB grid,although Northern Ireland postcodes are subject to a more restrictive licence permitting internal business use only.Postcodes for the Crown Dependences are also included, without co-ordinates. A further difference is that non-current postcodes and dates of introduction and withdrawal of postcodes are included.

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:

• Withsatellite navigationsystems, to navigate to an address by street number and postcode
• By life insurance companies and pension funds to assess longevity for pricing and reserving
• By other types of insurance companies to assess premiums for motoring/business/domestic policies
• To determinecatchment areasfor school places ordoctors'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, byjob centresto find jobs for job-seekers, to alert people oftown planningapplications in their area, and a great many other applications.

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,to disassociate with a poorer area,to reduce insurance premiums or to be associated with an area with a lowercost of living.In all these casesRoyal Mailhas 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.

Postcode areas rarely align with local government boundaries and a few straddleEngland's borders withWalesandScotland.This has led toBritish Sky Broadcastingsubscribers receiving the wrong BBC and ITV regions, and newly licensedradio amateursbeing given incorrectcall signs.

See also

• List of postcode areas in the United Kingdom
• List of postal codes(around the world)
• ACORN
• Address Point
• Postcode lottery
• RM4SCC—a machine-readable barcode version of the postcode and delivery point suffix
• Postcode Address File