Postal district

"Post code" redirects here. For computer POST codes, see Power-on self-test.

A postal code (known in various countries as a post code, postcode, or ZIP code) is a series of letters and/or digits appended to a postal address for the purpose of sorting mail. Once postal codes were introduced, other applications became possible.

In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems. Countries that do not have national systems include Ireland and Panama.

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 system.


There are a number of colloquial terms for postal code.

postal code
The general term is used directly in Canada.
This portmanteau is popular in many English-speaking countries.
ZIP code
The standard term in the United States and the Philippines; ZIP is an acronym for Zone Improvement Plan.
PIN code / pincode
The standard term in India; PIN is an acronym for Postal Index Number.


The development of postal codes reflects the natural evolution in which postal delivery grew more complicated as populations grew and the built environment became more complex. This process occurred first in large cities. The nucleus of a postal code idea thus began with postal district numbers (or postal zone numbers) within large cities. London was first subdivided into 10 districts in 1857, and Liverpool in 1864. By World War I or possibly earlier, such postal district or zone numbers existed in various European large 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[1][2]), 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 postal district or zone numbering plans beyond large cities to cover even small towns and rural locales was in the air. This was the concept that would create postal codes as we define them today. (The very 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,[3] but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941,[4] followed by Argentina in 1958, the United Kingdom in 1959,[5] the United States in 1963[6] and Switzerland in 1964.[7]


Character sets

The characters used in postal codes are

Reserved 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, SD and SA are not used for historical reasons.

Postal codes in Canada do not include the letters D, F, I, O, Q, or U, as the 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 alternates between a letter and a number (with a space after the 3rd character) in this format: A9A 9A9[8]

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 digits, encode many more locations. For example: If we are given a 2 digit numeric code then we could code 10 x 10= 100 locations. In contrast to a 2 digit alphanumeric code which if we take to have 30 possibilities per digit would then have 30 x 30= 900 possibilities. So they are often more precise, as is the case in the United Kingdom or in the Netherlands, where a postal code corresponds to a street or even a building, meaning the post code and the number of the home/business is all that is needed for accurate delivery. The independent nations using alphanumeric postal code systems are:

Country code prefixes

Usage of ISO 3166-1 alpha-2 codes was recommended to be used starting in 1994,[10] but they have not become widely used. The European Committee for Standardization recommends use of ISO Alpha-2 codes for international postcodes[10] and a UPU guide on international addressing states that "administrations may recommend" the use of ISO Alpha-2 codes.[11]

Andorra, Ecuador, Latvia, Moldova, Slovenia use the ISO 3166-1 alpha-2 as prefix in their postal codes.

In some countries (such as those of continental Europe, where a postcode format of four or five numeric digits is commonly used) the numeric postal code is sometimes prefixed with a country code to avoid confusion when sending international mail to or from that country. Recommendations by official bodies responsible for postal communications are confusing regarding this practice.[10] For many years, licence plate codes — for instance "D-" for Germany or "F-" for France — were used, although this was not accepted by the Universal Postal Union (UPU).[10]

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 Japan, China, Korea and the Russian Federation, it is written more to the beginning of an address.

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 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 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 country subdivisions.

Format of 6 digit numeric (8 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 (24 of 100 possible codes used = 24%)
BB - one of the 226 cantons of Ecuador (for AABB 226 of 10000 codes used, i.e. 2.26%. Three cantons are not in any province)
CC - one of the parishes of Ecuador.

Format of 5 digit numeric Postal codes in Costa Rica, introduced in 2007: ABBCC

A - one of the 7 provinces of Costa Rica (7 of 10 used, i.e. 70%)
BB - one of the 81 cantons of Costa Rica (81 of 100 used, i.e. 81%)
CC - one of the districts of Costa Rica.

In Costa Rica these codes are also used by the National Institute for Statistics and Census (INSEC).

The first two digits of the postal codes in Turkey correspond to the provinces and each province has assigned only one number. They are the same for them as in ISO 3166-2:TR.[12]

The first two digits of the postal codes in Vietnam indicate a 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 borders

In France the numeric code for the departments is used in the first 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 defines an area including several states. From the first three digits (with some exceptions), one can deduce the state.

Codes defined independently from administrative borders

The first two digits of the postal codes in Germany define areas independent from 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.

The UK post designed the postal codes in the United Kingdom mostly for efficient distribution. Nevertheless, with time, people associated codes with certain areas, leading certain people wanting or not wanting to have a certain code. See also postcode lottery.



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 the International School of The Hague.


Other countries allow equally precise coding. For example, in the United States, the delivery point barcode printed underneath an address by postal sorting equipment is typically derived from the last two digits of the house number and thus (at least theoretically) allows an unambiguous identification of every address in the country.

Otherwise, the United States uses a strictly numerical system called ZIP Codes. "ZIP" is an acronym for Zone Improvement Plan.[13] The basic ZIP Code is five numbers: The first represents a region, the second a state within that region, and the third a sorting center within that state. The remaining two digits represent a particular community. For Example: 48160 - "4" indicates the fourth ZIP Code region, composed of three states on the Great Lakes; "8" is assigned to eastern lower Michigan; "1" indicates the regional sorting center at Dearborn, Michigan; and "60" represents Milan, Michigan and the surrounding area served by its post office. Postal customers may add an additional 4-digit code (called "ZIP + 4"), which will sort the mail to a particular mail carrier.


Template:See For domestic properties the postcode refers to up to 100 properties in contiguous proximity (e.g. a short section of a populous road, or a series of less populous neighbouring roads). The postcode plus 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 apart. The postcode plus the first line of the address, however, is always unique (except where sub-properties occur).

Structure is alphanumeric with the following six valid permutations, as defined by 7666:

  A9 9AA
 A9A 9AA
 A99 9AA
 AA9 9AA
AA99 9AA

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 numbers, 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 about 100 postcode areas ranging widely in size from BT which covers the whole of Northern Ireland to ZE for Shetland. Postcode areas may also cross national boundaries, such as SY which covers a large, predominantly rural area from Shrewsbury and Ludlow in Shropshire, England, through to the eastern Welsh town of Welshpool, Powys in Wales to the seaside town of Aberystwyth, Ceredigion on Wales' west coast.

States and overseas territories sharing a postal code system

The British Crown dependencies of Guernsey, Jersey and the Isle of Man are part of the UK postcode system. They use the scheme AAN NAA, in which the first two letters are a unique code (GY, JE and IM respectively).

Eight British Overseas Territories use ten postal codes: three for Saint Helena, Ascension and Tristan da Cunha, and one apiece for the others. Note that the former has two ISO 3166-1 alpha-2 country codes, and the British Antarctic Territory has none, so the number of ISO codes is eight.

Four other British Overseas Territories have their own systems, some use the ISO 3166-1 alpha-2 prefix:

French overseas territories use the five-digit French postal code system, each code starting with the three letter department identifier. Monaco also uses the French system.

Italy, San Marino and Vatican City use one system. Liechtenstein and Switzerland use one system. Slovakia and the Czech Republic base their systems on the codes of Czechoslovakia, their ranges not overlapping.

Non-geographic codes

In Finland the special postal code 99999 is for Korvatunturi, the place where Santa Claus (Joulupukki in Finnish) is said to live.

In Greenland the postal code 2412 is for Julemanden (Santa Claus)

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.[14] Canada Post introduced a special address for mail to Santa Claus, complete with its own postal code:


In the United Kingdom, the non-conforming postal code GIR 0AA was used for the National Girobank until its closure in 2003.[15]


Main article: List of postal codes

Non-postal uses and economic aspects

While postal codes were introduced to expedite the delivery of mail, they are very useful tools for several other purposes, particularly in countries where codes are very fine-grained and identify just a few addresses. Among uses are:

  • 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 as the crow flies (or, if used in conjunction with streetmap software, road distance). This can be used by companies to inform potential customers where to go, by job centres to find jobs for job-seekers, to alert people of town planning applications in their area, and a great many other applications.[16]
  • 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.


The availability of postal code information has significant economic advantages. In some countries, the postal authorities charge for access to the code database. As of January 2010, the United Kingdom Government is consulting on whether to waive licensing fees for some geographical data sets (to be determined) related to UK postcodes.

See also


External links

  • Universal Postal Union
    • Addressing
    • Postcodes
  • Reference on World Postcodes
  • Canada Post

Template:Postal system

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.