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{{short description|Series of letters and digits for sorting mail}}
{{redirect|Post code|computer POST codes|Power-on self-test}}
{{Use dmy dates|date=May 2024}}
{{more citations needed|date=July 2015}}
[[File:Farrer post code.jpg|thumb|300px|Post office sign in [[Farrer, Australian Capital Territory]], showing [[Postcodes in Australia|postcode]] 2607]]

A '''postal code''' (also known locally in various English-speaking countries throughout the world as a '''postcode''', '''post code''', '''PIN''' or '''ZIP Code''') is a series of letters or [[numerical digit|digits]] or both, sometimes including spaces or punctuation, included in a [[postal address]] for the purpose of sorting [[mail]].

{{As of|2021|8|post=,|url=https://www.upu.int/en/Postal-Solutions/Programmes-Services/Addressing-Solutions?csid=20&cid=315}} the [[Universal Postal Union]] lists 160 countries which require the use of a postal code.<ref>{{citation|title=General Addressing Issues|date=3 August 2021|access-date=1 June 2022|url=https://www.upu.int/UPU/media/upu/documents/PostCode/General-Addressing-Issues.pdf|publisher=[[Universal Postal Union]]|article=Addressing knowledge centre|article-url=https://www.upu.int/en/Postal-Solutions/Programmes-Services/Addressing-Solutions?csid=20&cid=315}}</ref>

Although postal codes are usually assigned to geographical areas, special codes are sometimes assigned to individual addresses or to institutions that receive large volumes of mail, such as government agencies and large commercial companies. One example is the French [[Cedex (France)|CEDEX]] system.

== Terms ==
There are a number of synonyms for postal code; some are country-specific:
* '''[[Codice di Avviamento Postale|CAP]]''': The standard term in Italy; CAP is an acronym for {{lang|it|codice di avviamento postale}} ('postal expedition code').
* '''[[Código de Endereçamento Postal|CEP]]''': The standard term in Brazil; CEP is an acronym for {{lang|pt|código de endereçamento postal}} ('postal addressing code').
* '''[[Eircode]]''': The standard term in Ireland.
* '''[[Postal codes in Switzerland and Liechtenstein|NPA]]''' in [[French-speaking Switzerland]] ({{lang|fr|numéro postal d'acheminement}}) and [[Ticino|Italian-speaking Switzerland]] ({{lang|it|numero postale di avviamento}}).
* '''[[Postal Index Number|PIN]]''': The standard term in India; PIN is an acronym for Postal Index Number. Sometimes called a PIN code.
* '''PLZ''': The standard term in Germany, Austria, [[German-speaking Switzerland]] and [[Liechtenstein]]; PLZ is an abbreviation of {{lang|de|Postleit&zwnj;zahl}} ('postal routing number').
* '''[[Postal codes in Canada|Postal code]]''': The general term is used in Canada.
* '''Postcode''': This [[compound (linguistics)|solid compound]] is popular in many English-speaking countries and is also the standard term in the Netherlands.
* '''Postal index''': This term is used in Eastern European countries such as Belarus, Moldova, Russia, Ukraine, etc.
*'''[[:cs:Poštovní směrovací číslo|PSČ]]''': The standard term in Slovakia and the Czech Republic; PSČ is an acronym for {{lang|sk|Poštové smerovacie číslo}} (in Slovak) or {{lang|cs|Poštovní směrovací číslo}} (in Czech), both meaning postal routing number.
* '''[[ZIP Code]]''': The standard term in the United States and the Philippines; ZIP is an [[acronym]] for ''Zone Improvement Plan''.

== History ==
[[File:Stamp Soviet Union 1977 CPA 4775.jpg|thumb|1977 Soviet stamp promoting the use of postal codes]]
The development of postal codes happened first in large cities. Postal codes began with postal district numbers (or postal zone numbers) within large cities. [[London]] was first subdivided into 10 districts in 1857 (EC (East Central), WC (West Central), N, NE, E, SE, S, SW, W, and NW), four were created to cover [[Liverpool]] in 1864; and [[Manchester]]/[[Salford]] was split into eight numbered districts in 1867/68. By [[World War I]], such postal district or zone numbers also existed in various large European cities. They existed in the United States at least as early as the 1920s, possibly implemented at the local post office level only (for example, instances of "Boston 9, Mass" in 1920 are attested<ref name="1920_advert_Hill_Clarke_Co">{{Cite journal |author=Hill, Clarke & Co., Inc. |title=Advertisement for a drill press, 1920 |journal=American Machinist |page=389 |url=https://books.google.com/books?id=ezRMAQAAIAAJ&pg=RA2-PA389 |date=1 July 1920}}</ref><ref name="1920_advert_Lynd_Farquhar_Co">{{Cite journal |author=Lynd-Farquhar Company |title=Advertisement for machine tools |journal=American Machinist |page=284 |url=https://books.google.com/books?id=ezRMAQAAIAAJ&pg=RA3-PA284|date=30 September 1920}}</ref>) although they were evidently not used throughout all major US cities (implemented [[USPOD]]-wide) until [[World War II]].

By 1930 or earlier, the idea of extending the postal district or zone numbering plans beyond large cities to cover even small towns and rural locales had started. These developed into postal codes as they are defined today. The name of US postal codes, "ZIP Codes", reflects this evolutionary growth from a zone plan to a zone improvement plan, "ZIP". Modern postal codes were first introduced in the [[Ukrainian Soviet Socialist Republic]] in December 1932,<ref>{{cite web |url=http://www.upns.org/article/85-first-postal-zip-code |title=The First Postal (ZIP) Code in the World |publisher=Ukrainian Philatelic and Numismatic Society |date=20 April 2009 |access-date=4 March 2010 |url-status=live |archive-url=https://web.archive.org/web/20100423155849/http://www.upns.org/article/85-first-postal-zip-code |archive-date=23 April 2010 }}</ref> but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941,<ref>{{cite web |url=http://www.deutschepost.de/dpag?tab=1&skin=hi&check=no&lang=de_EN&xmlFile=link1017517_1004711 |work=Deutsche Post|title=The history of the postcode |access-date=10 October 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110716191434/http://www.deutschepost.de/dpag?tab=1&skin=hi&check=no&lang=de_EN&xmlFile=link1017517_1004711 |archive-date=16 July 2011 }}</ref> followed by Singapore in 1950,<ref name="Singapore NLB">{{cite web |url=http://eresources.nlb.gov.sg/infopedia/articles/SIP_1006_2010-05-27.html |title=Six-digit postal code system |last=Chia |first=Joshua |date=13 July 2016 |website=Singapore Infopedia |publisher=National Library Board |access-date=3 October 2018 }}</ref> Argentina in 1958, the United States in 1963<ref>{{cite web |url=http://glossary.ippaper.com/default.asp?req=glossary/term/2592&catitemid= |title=ZIP (Zone Improvement Plan) Code |publisher=International Paper Company |access-date=10 October 2010 |url-status=dead |archive-url=https://web.archive.org/web/20091119144342/http://glossary.ippaper.com/default.asp?req=glossary%2Fterm%2F2592&catitemid= |archive-date=19 November 2009 }}</ref> and Switzerland in 1964.<ref>{{cite web |url=http://www.fundinguniverse.com/company-histories/SCHWEIZERISCHE-POST-TELEFON-UND-TELEGRAFENBETRIEBE-Company-History.html |title=Company History: Schweizerische Post-Telefon-und-Telegrafen-Betriebe |publisher=Funding Universe |access-date=10 October 2010 |url-status=live |archive-url=https://web.archive.org/web/20110909092830/http://www.fundinguniverse.com/company-histories/SCHWEIZERISCHE-POST-TELEFON-UND-TELEGRAFENBETRIEBE-Company-History.html |archive-date=9 September 2011 }}</ref> The United Kingdom began introducing its current system in [[Norwich]] in 1959, but it was not used nationwide until 1974.<ref>{{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 |newspaper=The Independent |archive-url=https://web.archive.org/web/20110225013444/http://www.independent.co.uk/money/mortgages/a-short-history-of-the-postcode-751884.html |archive-date=25 February 2011 |url-status= dead |access-date=25 June 2014 }}</ref>

== Presentation ==
[[File:Postal codes by country.svg|thumb|350px|right|Postal codes by country and digit-type.<br />'''Numeric digits''': <br /> &nbsp; {{legend inline|#87aade|3}} {{legend inline|#5f8dd3|4}} {{legend inline|#3771c8|5}} {{legend inline|#2c5aa0|6}} {{legend inline|#214478|7}} {{legend inline|#162d50|8}} {{legend inline|#0b1728|9}} {{legend inline|#070f1a|10}} <br />'''Alphanumeric digits''': {{legend inline|#2ca02c|6}} {{legend inline|#217821|7}} {{legend inline|#165016|8}}<br />'''Postal codes not in use''': {{legend inline|#e0e0e0|}}]]

=== Character sets ===
The characters used in postal codes are:
* The [[Western Arabic numerals]] "0" to "9"
* Letters of the [[ISO basic Latin alphabet]]
* Spaces, hyphens

==== Reserved and Excluded characters ====
[[Postal codes in the Netherlands]] originally did not use the letters 'F', 'I', 'O', 'Q', 'U' and 'Y' for technical reasons. But as almost all existing combinations are now used, these letters were allowed for new locations starting 2005. The letter combinations "SS" ({{lang|de|[[Schutzstaffel]]}}), "SD" ({{lang|de|[[Sicherheitsdienst]]}}), and "SA" ({{lang|de|[[Sturmabteilung]]}}) are not used, due to links with the [[Netherlands in World War II|Nazi occupation in World War II]].

[[Postal codes in Canada]] do not include the letters D, F, I, O, Q, or U, as the [[optical character recognition]] (OCR) equipment used in automated sorting could easily confuse them with other letters and digits. The letters W and Z are used, but are not currently used as the first letter. The Canadian Postal Codes use alternate letters and numbers (with a space after the third character), formatted ANA NAN.<ref name=GreatData.com>{{cite web|title=GreatData.com (a licensee of Canada Post data)|url=http://greatdata.com|access-date=8 February 2013|url-status=live|archive-url=https://web.archive.org/web/20130402154507/http://greatdata.com/|archive-date=2 April 2013}}</ref>

In Ireland, the [[eircode]] system uses the following letters only: A, C, D, E, F, H, K, N, P, R, T, V, W, X, Y. This serves to avoid confusion in OCR, and to avoid accidental double-entendres by avoiding the creation of word lookalikes, as Eircode's last four characters are random.

==== Alphanumeric postal codes ====
Most of the postal code systems are numeric; only a few are alphanumeric (i.e., use both letters and digits). Alphanumeric systems can, given the same number of characters, encode many more locations. For example, while a two digit numeric code can represent 100 locations, a two character alphanumeric code using ten digits and twenty letters can represent 900 locations.

The independent nations using alphanumeric postal code systems are:
* [[Argentina]] ([[Postal codes in Argentina|see table]])
* [[Brunei]] ([[Postal codes in Brunei|see table]])
* [[Canada]] ([[Postal codes in Canada|see table]])
* [[Eswatini]]
* [[Ireland]] ([[Postal addresses in the Republic of Ireland|see table]])
* [[Jamaica]] ([[Postal codes in Jamaica|see table]]) (suspended in 2007<ref>{{cite web |url=http://www.jamaicapost.gov.jm/corporate_news/pressrelease_07.htm |title=Post Code Project Suspended Indefinitely |work=Jamaica Post|date=12 February 2007 |access-date=4 March 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100226125027/http://www.jamaicapost.gov.jm/corporate_news/pressrelease_07.htm |archive-date=26 February 2010 }}</ref>)
* [[Kazakhstan]] (since 2015)
* [[Malta]] ([[Postal codes in Malta|see table]])
* [[Netherlands]] ([[Postal codes in the Netherlands|see table]])
* [[Peru]] ([[List of postal codes in Peru|see table]]), the postal code format in Peru was updated in February 2011 to be of the format of five digits.
* [[Somalia]]
* [[United Kingdom]] ([[Postcodes in the United Kingdom|see table]])

Countries which prefix their postal codes with a fixed group of letters, indicating a country code, include [[Andorra]], [[Azerbaijan]], [[Barbados]], [[Ecuador]] and [[Saint Vincent and the Grenadines]].

=== Country code prefixes ===
[[ISO 3166-1 alpha-2]] country codes were recommended by the [[European Committee for Standardization]] as well as the [[Universal Postal Union]] to be used in conjunction with postal codes starting in 1994,<ref name="daCruz_ColumbiaUni">{{cite web| last =da Cruz| first =Frank| title =Frank's Compulsive Guide to Postal Addresses| publisher =Columbia University| date =17 May 2008| url =http://www.columbia.edu/kermit/postal.html#europe| access-date =4 June 2008| url-status =live| archive-url =https://web.archive.org/web/20080725104707/http://www.columbia.edu/kermit/postal.html#europe| archive-date =25 July 2008}}</ref> but they have not become widely used. [[Andorra]], [[Azerbaijan]], [[Barbados]], [[Ecuador]], [[Latvia]] and [[Saint Vincent and the Grenadines]] use the [[ISO 3166-1 alpha-2]] as a prefix in their postal codes.

In some countries (such as in [[continental Europe]], where a numeric postcode format of four or five digits is commonly used) the numeric postal code is sometimes prefixed with a [[country code]] when sending international mail to that country.

=== Placement of the code ===
Postal services have their own formats and placement rules for postal codes. In most English-speaking countries, the postal code forms the last item of the address, following the city or town name, whereas in most continental European countries it precedes the name of the city or town. When it follows the city, it may be on the same line or on a new line.

In [[Japanese addressing system|Japan]], it is written at the start of the address when written in Japanese, but at the end when the address is written in the Latin alphabet.

== Geographic coverage ==
Postal codes are usually assigned to geographical areas. Sometimes codes are assigned to individual addresses or to institutions that receive large volumes of mail, e.g. government agencies or large commercial companies. One example is the French [[Cedex (France)|Cedex]] system.

=== Postal zone numbers ===
Before postal codes as described here were used, large cities were often divided into postal zones or postal districts, usually numbered from 1 upwards within each city. The newer postal code systems often incorporate the old zone numbers, as with [[London postal district]] numbers, for example. Ireland still uses [[List of Dublin postal districts|postal district numbers]] in [[Dublin]]. In New Zealand, [[Auckland]], [[Wellington]] and [[Christchurch]] were divided into postal zones, but these fell into disuse, and have now become redundant as a result of a new postcode system being introduced.

=== Codes defined along administrative borders ===
Some postal code systems, like those of [[Ecuador]] and [[Costa Rica]], show an exact agreement with the hierarchy of [[administrative division]]s.

Format of six digit numeric (eight digit alphanumeric) [[postal codes in Ecuador]], introduced in December 2007: ECAABBCC
: EC – [[ISO 3166-1 alpha-2]] country code
: AA – one of the 24 [[provinces of Ecuador]]
: BB – one of the 226 [[cantons of Ecuador]]
: CC – one of the [[parishes of Ecuador]].

Format of five digit numeric [[Postal codes in Costa Rica]], introduced in 2007: ABBCC
: A – one of the seven [[provinces of Costa Rica]]
: BB – one of the 81 [[cantons of Costa Rica]]
: CC – one of the [[districts of Costa Rica]].
In Costa Rica these codes were originally used as district identifiers by the [[National Institute of Statistics and Census of Costa Rica]] and the [[Administrative divisions of Costa Rica|Administrative Territorial Division]], and continue to be equivalent.<ref name="divadm">{{cite web |language=es |title=Declara oficial para efectos administrativos, la aprobación de la División Territorial Administrativa de la República N°41548-MGP |url=http://www.pgrweb.go.cr/scij/Busqueda/Normativa/Normas/nrm_texto_completo.aspx?param1=NRTC&nValor1=1&nValor2=88416&nValor3=115607&param2=1&strTipM=TC&lResultado=1&strSim=simp |website=Sistema Costarricense de Información Jurídica |access-date=26 September 2020 |date=19 March 2019}}</ref><ref name="dta2017">{{cite book |language=es |title=División Territorial Administrativa de la República de Costa Rica|date=8 March 2017|publisher=Editorial Digital de la Imprenta Nacional|isbn=978-9977-58-477-5|url=https://www.imprentanacional.go.cr/editorialdigital/libros/historiaygeografia/division_17.pdf}}</ref>

The first two digits of the [[postal codes in Turkey]] correspond to the [[provinces of Turkey|provinces]] and each province has assigned only one number. They are the same for them as in [[ISO 3166-2:TR]].<ref>{{cite web |url=http://www.postakodumne.com |archive-url=https://web.archive.org/web/20110404005656/http://www.postakodumne.com/ |archive-date=4 April 2011 |title=Posta Kodum Ne |language=Turkish |access-date=25 August 2021}}</ref>

The first two digits of the [[postal codes in Vietnam]] indicate a [[provinces of Vietnam|province]]. Some provinces have one, other have several two digit numbers assigned. The numbers differ from the number used in [[ISO 3166-2:VN]].

=== Codes defined close to administrative boundaries ===
[[File:MAPA DAS REGIÕES DE CEP.JPG|thumb|right|280px|Map of Brazilian five-digit postalcodes of [[São Paulo (state)|São Paulo state]]. Each color shows a set of administrative areas, and the hierarchy of codes relating indirectly to them.]]

In France the numeric code for the departments is used as the first two digits of the postal code, except for the two departments in [[Corsica]] that have codes 2A and 2B and use 20 as postal code. Furthermore, the codes are only the codes for the department in charge of delivery of the post, so it can be that a location in one department has a postal code starting with the number of a neighbouring department.

=== Codes defined indirectly to administrative borders ===
The first digit of the [[postal codes in the United States]] comprises discrete states. From the first three digits one can infer the state, with a few exceptions where an area is served by a central office in an adjacent state.

Similarly, in [[Canada Post|Canada]], the first letter indicates the province or territory, although the provinces of [[Quebec]] and [[Ontario]] are divided into several lettered sub-regions (e.g. H for [[Montreal]] and [[Laval, Quebec|Laval]]), and the [[Northwest Territories]] and [[Nunavut]] share the letter X.

=== Codes defined independently from administrative areas ===
The first two digits of the [[postal codes in Germany]] define areas independently of administrative regions. The coding space of the first digit is fully used (0–9); that of the first two combined is utilized to 89%, i.e. there are 89 postal zones defined. Zone 11 is non-geographic.

[[Royal Mail]] designed the [[postal codes in the United Kingdom]] mostly for efficient distribution. Nevertheless, people associated codes with certain areas, leading to some people wanting or not wanting to have a certain code. See also [[postcode lottery]].

In Brazil the [[:pt:Código de Endereçamento Postal|8-digit postcodes]] are an evolution of the five-digit area postal codes. In the 1990s the Brazilian five-digit postal code (illustrated), <code>DDDDD</code>, received a three-digit suffix <code>DDDDD-SSS</code>, but this suffix is not directly related to the administrative district hierarchy. The suffix was created only for logistic reasons.

<gallery mode="packed" heights="220px" style="text-align:center" caption="Brazilian eight-digit postal codes – A city block and its faces">
QuadrasExemplo-CEP.png|[[City block]]s surrounded by streets, some streets with a different eight-digit postal code (suffixes 001 to 899)
QuadraExemplo-CEP.png|Faces of a [[city block]] and their extension into its interior. Each color is an eight-digit postal code, usually assigned to a side (odd or even numbered) of a street.
QuadraFaces-CEP.png|Faces of a city block and their extension between city blocks. The same colors (polygons) indicate the same postal codes.
</gallery>

[[file:QuadraExemplo-CEP-pnt.png|thumb|220px|In the [[Spatialization|code spatialization]] it '''is an error''' to associate the postal code to an individual ''land lot'' area: a lot may have 0, 1, 2 or more delivery points, with different codes.]]

The postal code assignment can be assigned to individual [[land lot]]s in some special cases – in Brazil, they are named "large receivers" and receive suffixes 900–959. It is an error to associate the postal code with the whole land lot area (illustrated). A postal code is often related to a [[land lot]], but postal codes are usually related to access points on streets. Small or middle-sized houses, in general, only have a single main gate, which is the delivery point. Parks, large businesses such as shopping centers and big houses, may have more than one entrance and more than one delivery point.

=== Precision ===
==== Czechoslovakia ====
Czechoslovakia introduced Postal Routing Numbers (PSČ – poštovní směrovací čísla) in 1973. The code consists of 5 digits formatted into two groups: NNN NN. Originally, the first group marked a district transport centre, the second group represented the order of post offices on the collection route. In the first group, the first digit corresponds partly with the region, the second digit meant a collection transport node (sběrný přepravní uzel, SPU) and the third digit a "district transport node" (okresní přepravní uzel). However, processing was later centralized and mechanized while codes remained the same. After separation, Slovakia and the Czech Republic kept the system. Codes with an initial digit of 1, 2, 3, 4, 5, 6, or 7 are used in the Czech Republic, while codes with an initial digit of 8, 9, or 0 are used in Slovakia.

A code corresponds to a local postal office. However, some larger companies or organizations have their own post codes. In 2004–2006, there were some efforts in Slovakia to reform the system, to get separate post codes for every district of single postmen, but the change was not realized.

====India====
{{Further|Postal Index Number}}

[[File:Example of Indian Postal Index Number.svg|thumb|An example of a Postal Index Number from [[kangra]] in [[Himachal Pradesh]]. '''4''' indicates the ''West postal zone'', '''5''' indicates ''a postal sub-zone in Madhya Pradesh'', '''6''' indicates the ''Ujjain sorting district'', '''0''' indicates the ''Ujjain core area service route'', '''01''' indicates the ''Ujjain Head Office as the delivery office''.]]

Postal codes are known as [[Postal Index Number]]s (PINs; sometimes as PIN codes) in India. The PIN system was introduced on 15 August 1972 by India Post. India uses a unique six-digit code as a geographical number to identify locations in India. The format of the PIN is ZSDPPP defined as follows:

: Z – Zone
: S – Sub-zone
: D – Sorting District
: P – Service Route
: PP – Post Office

The first digit represents nine total zones: eight regional and one functional.

==== Ireland ====
{{Further|Postal addresses in the Republic of Ireland}}

In Ireland, the new postal code system launched in 2015, known as [[Eircode]] provides a unique 7-character alphanumerical code for each individual address. The first three digits are the routing key, which is a postal district and the last four characters are a unique identifier that relates to an individual address (business, house or apartment). A fully developed API is also available for integrating the Eircode database into business databases and logistics systems.

With a single exception, these codes are in the format:

ANN XXXX

The single exception is the Dublin D6W postal district. It is the only routing key area in the country that takes the format ANA instead of ANN:

D6W XXXX

While it is not intended to replace addresses, in theory simply providing a seven-character Eircode would locate any Irish delivery address. For example, the Irish Parliament [[Dáil Éireann]] is: D02 A272

==== Netherlands ====
{{further|Postal codes in the Netherlands}}

[[Postal codes in the Netherlands]], known as postcodes, are alphanumeric, consisting of four digits followed by a space and two letters (NNNN AA). Adding the house number to the postcode will identify the address, making the street name and town name redundant. For example: 2597 GV 75 will direct a postal delivery to Theo Mann-Bouwmeesterlaan 75, [['s-Gravenhage]] (the International School of The Hague).

==== Singapore ====
{{Further|Postal codes in Singapore}}

Since 1 September 1995, every building in Singapore has been given [[postal codes in Singapore|a unique, six-digit postal code]].<ref name="Singapore NLB" />

==== United Kingdom ====
{{More citations needed section|date=January 2025}}
{{Further|Postcodes in the United Kingdom}}
For domestic properties, an individual postcode may cover up to 100 properties in contiguous proximity (e.g. a short section of a populous road, or a group of less populous neighbouring roads). The postcode together with the number or name of a property is not always unique, particularly in rural areas. For example, GL20 8NX/1 might refer to either 1 Frampton Cottages or 1 Frampton Farm Cottages, roughly a quarter of a mile (400 metres) apart.

The structure is alphanumeric, with the following six valid formats, as defined by [[British Standards|BS]] 7666:<ref>{{cite web |title=BS7666 Address |work=Data Standards Catalogue |publisher=UK National Archives |date=2 October 2009 |url=http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |archive-url=http://webarchive.nationalarchives.gov.uk/20130128101412/http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |url-status=dead |archive-date=28 January 2013 |access-date=15 August 2015 }}</ref>

   AN NAA
  ANA NAA
  ANN NAA
  AAN NAA
 AANA NAA
 AANN NAA

There are always two halves: the separation between outward and inward postcodes is indicated by one space.

The outward postcode covers a unique area and has two parts which may in total be two, three or four characters in length. A postcode area of one or two letters, followed by one or two digits, followed in some parts of London by a letter.

The outward postcode and the leading numeric of the inward postcode in combination forms a postal sector, and this usually corresponds to a couple of thousand properties.

Larger businesses and isolated properties such as farms may have a unique postcode. Extremely large organisations such as larger government offices or bank headquarters may have multiple postcodes for different departments.

There are 121 postcode areas in the UK, ranging widely in size from [[BT postcode area|BT]] which covers the whole of Northern Ireland to [[WC postcode area|WC]] for a small part of [[Central London]]. Postcode areas occasionally cross national boundaries, such as [[SY postcode area|SY]] which covers a large, predominantly rural area from [[Shrewsbury]] and [[Ludlow]] in [[Shropshire]], England, through to the seaside town of [[Aberystwyth]], [[Ceredigion]] on [[Wales]]' west coast.  There are a number of special purpose postcode areas that are "non-geographic" and which provide special routing instructions (such as parcel returns to online retailers).  The three Crown dependencies and Gibraltar also use UK formatted postcodes.  Some British Overseas Territories have adopted a single postcode for their territory that is very similar to the UK format.

==== United States ====
{{further|ZIP Code}}

In the United States, the basic [[ZIP Code]] is composed of five digits. The first three digits identify a specific [[sectional center facility]]—or central sorting facility—that serves a geographic region (typically a large part of a state). The next two digits identify a specific post office either serving an area of a city (if in an urban area or large suburban area) or an entire village, town, or small city and its surrounding area (if in a small suburban or rural area).

There is an extended format of the ZIP Code known as the [[ZIP+4]], which contains the basic five-digit ZIP Code, followed by a hyphen and four additional digits. These digits identify a specific delivery route, such as one side of a building, a group of apartments, or several floors of a large office building. Although using the ZIP+4 offers higher accuracy, addressing redundancy, and sorting efficiency within the [[USPS]], it is optional and not widely used by the general public. It is primarily only used by business mailers.

For high volume business mailers using automated mailing machines, the USPS has promulgated the [[Intelligent Mail barcode]] standard, which is a barcode containing the ZIP+4 code plus a two digit [[delivery point]]. This 11-digit number is theoretically a unique identifier for every address in the country.

=== States and overseas territories sharing a postal code system ===
French overseas departments and territories use the five-digit [[French postal code system]], each code starting with the three-digit department identifier. [[Monaco]] is also integrated in the French system and has no system of its own.

The British [[Crown Dependencies]] of [[Guernsey]], [[Jersey]] and the [[Isle of Man]] are part of the UK postcode system. They use the schemes AAN NAA and AANN NAA, in which the first two letters are a unique code (GY, JE and IM respectively). Most of the Overseas Territories have UK-style postcodes, with a single postcode for each territory or dependency, although they are still treated as international destinations by Royal Mail in the UK, and charged at international rather than UK inland rates. The four other Overseas Territories [[Anguilla]], [[Bermuda]], [[British Virgin Islands]] and [[Cayman Islands]] have their own separate systems and formats.

The Pacific island states of [[Palau]], [[Marshall Islands]] and the [[Federated States of Micronesia]] remain part of the US [[ZIP code]] system, despite having become independent states.

[[San Marino]] and the [[Vatican City]] are part of the [[Italy|Italian]] postcode system, while [[Liechtenstein]] similarly uses the [[Switzerland|Swiss]] system, as do the Italian exclave of [[Campione d'Italia]] and the German exclave of [[Büsingen am Hochrhein]], although they also form part of their respective countries' postal code systems.

The [[Czech Republic]] and [[Slovakia]] still use the codes of the former [[Czechoslovakia]], their ranges not overlapping. In 2004–2006, Slovakia prepared a reform of the system but the plan was postponed and may have been abandoned. In the Czech Republic, there was no significant effort to modify the system.

== Non-geographic codes ==
In the United Kingdom, the non-conforming postal code GIR 0AA was used for the [[National Girobank]] until its closure in 2003.<ref>[https://www.mirror.co.uk/news/uk-news/40-facts-postcode-mark-40th-4113087 40 facts about the postcode to mark 40th anniversary as vital part of daily life] {{webarchive|url=https://web.archive.org/web/20180316214017/https://www.mirror.co.uk/news/uk-news/40-facts-postcode-mark-40th-4113087 |date=16 March 2018 }}, Daily Mirror, 26 August 2014</ref> A non-geographic series of postcodes, starting with BX, is used by some banks and government departments.

:HM Revenue and Customs – VAT Controller
:VAT Central Unit
:BX5 5AT<ref>{{cite web|url=https://www.gov.uk/government/organisations/hm-revenue-customs/contact/vat-insolvency|title=VAT: insolvency|website=gov.uk|access-date=2 May 2018|url-status=live|archive-url=https://web.archive.org/web/20180106095712/https://www.gov.uk/government/organisations/hm-revenue-customs/contact/vat-insolvency|archive-date=6 January 2018}}</ref>

The XX postcode is used for parcel returns.  The BF postcode is used for British Forces Post Office (BFPO) addresses.

A fictional address is also used by Royal Mail for letters to Santa Claus, more commonly known as Santa or Father Christmas:

:Santa's Grotto
:Reindeerland XM4 5HQ<ref>[https://www.telegraph.co.uk/topics/christmas/10494193/Who-answers-all-the-letters-sent-to-Father-Christmas.html Who answers all the letters sent to Father Christmas?] {{webarchive|url=https://web.archive.org/web/20161225004304/http://www.telegraph.co.uk/topics/christmas/10494193/Who-answers-all-the-letters-sent-to-Father-Christmas.html |date=25 December 2016 }}, ''[[The Daily Telegraph]]'', 5 December 2013</ref>

Previously, the postcode SAN TA1 was used.<ref>[https://news.bbc.co.uk/2/hi/uk_news/2565041.stm Santa: 'I'm not a Superman, but I do exist'] , [[BBC News Online]], 11 December 2002</ref>

In Finland, the special postal code 96930 is for [[Korvatunturi]], the place where Santa Claus ({{Lang|fi|Joulupukki}} in [[Finnish language|Finnish]]) is said to live, although mail is delivered to the [[Santa Claus Village]] in [[Rovaniemi]]. The special postal code 99999 was formerly used.<ref>{{Cite web |title=Welcome to the Santa Claus´ Main Post Office |url=https://my.posti.fi/en/santa-claus-main-post-office |access-date=2024-08-08 |website=my.posti.fi |language=en}}</ref><ref>{{Cite book |last=Planet |first=Lonely |url=https://books.google.com/books?id=W7cDCgAAQBAJ&dq=99999+korvatunturi&pg=PA84 |title=Not For Parents Travel Book |date=2012-11-01 |publisher=Lonely Planet Publications |isbn=978-1-74220-855-8 |pages=84}}</ref>

In Canada, the amount of mail sent to Santa Claus increased every [[Christmas]], up to the point that Canada Post decided to start an official Santa Claus letter-response program in 1983. Approximately one million letters come in to Santa Claus each Christmas, including from outside of Canada, and all of them are answered in the same languages in which they are written.<ref>{{cite web |url=http://www.canadapost.ca/cpo/mc/aboutus/news/pr/2005/2005_jan_news_santa.jsf |title=Over one million children write letters to Santa |author=Canada Post |date=27 January 2007 |access-date=27 April 2009 |author-link=Canada Post |url-status=dead |archive-url=https://web.archive.org/web/20100409020858/http://www.canadapost.ca/cpo/mc/aboutus/news/pr/2005/2005_jan_news_santa.jsf |archive-date=9 April 2010 }}</ref> Canada Post introduced a special address for mail to Santa Claus, complete with its [[H0H 0H0|own postal code]]:

:SANTA CLAUS
:NORTH POLE &nbsp;H0H 0H0

In Belgium [[bpost]] sends a small present to children who have written a letter to [[Sinterklaas]]. They can use the non-geographic postal code 0612, which refers to the date Sinterklaas is celebrated (6 December), although a fictional town, street and house number are also used. In Dutch, the address is

:Sinterklaas
:Spanjestraat 1
:0612 Hemel<ref>{{cite web|url=http://www.bpost.be/sinterklaas/sinterklaas.html|title=Ook dit jaar, helpt bpost de Sint |publisher=[[bpost]]|website=bpost.be|access-date=2 May 2018}}</ref>

This translates as "1 Spain Street, 0612 Heaven". In French, the street is called "Paradise Street":

:Saint-Nicolas
:Rue du Paradis 1
:0612 Ciel<ref>{{cite web|url=http://www.bpost.be/saint-nicolas/saint-nicolas.html|title=Cette année également, bpost apporte son aide à Saint-Nicolas |publisher=[[bpost]]|website=bpost.be|access-date=2 May 2018}}</ref>

== Formats ==
{{main|List of postal codes}}

== Non-postal uses ==
{{Expand section|date=December 2009}}
While postal codes were introduced to expedite the delivery of mail, they can be used for:
* Finding the nearest branch of an organisation to a given address. A computer program uses the postal codes of the target address and the branches to list the closest branches in order of distance. This can be used by companies to inform potential customers where to go, by [[Public employment service|job centre]]s to find jobs for job-seekers, to alert people of [[town planning]] applications in their area, and for other applications.<ref name=planning>{{cite news |author=Charles Arthur |url=https://www.theguardian.com/technology/2009/oct/07/newly-asked-question-royal-mail-postzon |title=Guardian newspaper article on postcodes |work=The Guardian|location=London |access-date=26 February 2018 |url-status=live |archive-url=https://web.archive.org/web/20171201043135/https://www.theguardian.com/technology/2009/oct/07/newly-asked-question-royal-mail-postzon |archive-date=1 December 2017 }}</ref>
* Fine-grained postal codes can be used with [[satellite navigation]] systems to navigate to an address by street number and postcode.
* Geographical sales territories for representatives in the pharmaceutical industry are allocated based on a workload index that is based upon postcode.
* Population data can be isolated, grouped and/or organized by postal code for statistical analysis.

=== Availability ===
{{Update|section|date=April 2021|updated=2010}}
In some countries, the postal authorities charge for access to the code database. {{As of|2010|1}}, the United Kingdom Government is consulting on whether to [[Postcode Address File#Costs and public availability|waive licensing fees]] for some geographical data sets (to be determined) related to UK postcodes.

== See also ==
* [[List of postal codes]]
* [[:Category:Lists of postal codes]]
* [[Address format by country and area]]
* [[Postcode Address File]]

== References ==
{{reflist}}

== External links ==
{{Wikidata property|P281}}
* [http://www.upu.int/ Universal Postal Union]
** [http://www.upu.int/en/activities/addressing/about-addressing.html Addressing] {{Webarchive|url=https://web.archive.org/web/20120303011533/http://www.upu.int/en/activities/addressing/about-addressing.html |date=3 March 2012 }}
** [http://www.upu.int/en/resources/postcodes/about-postcodes.html Postcodes] {{Webarchive|url=https://web.archive.org/web/20110903001230/http://www.upu.int/en/resources/postcodes/about-postcodes.html |date=3 September 2011 }}

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[[Category:Postal systems]]
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[[Category:Ukrainian inventions]]
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