Editing Postal code (section)

== 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 [[Ujjain]] in [[Madhya 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.