Postal code



A postal code (known in various countries as a post code, postcode, or ZIP code in United States) 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 Ghana.

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.

Terms
There are a number of synonyms for postal code; some are country-specific.


 * CEP:The standard term in Brazil; CEP is an Acronym for Código de Endereçamento Postal (Postal Addressing Code)
 * postal code: The general term is used directly in Canada.
 * postcode: This portmanteau is popular in many English-speaking countries.
 * PIN code / pincode: The standard term in India; PIN is an acronym for Postal Index Number.
 * CAP: The standard term in Italy. Codice di Avviamento Postale, literally: Postal Expedition Code.
 * ZIP code: The standard term in the United States and the Philippines; ZIP is an acronym for Zone Improvement Plan.

History
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 ), 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, but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941, followed by Argentina in 1958, the United States in 1963 and Switzerland in 1964. The United Kingdom began introducing its current system in Norwich in 1959, but completed the nationwide introduction in 1974 only.

Character sets
The characters used in postal codes are
 * The arabic numerals "0" to "9"
 * Letters of the ISO basic Latin alphabet
 * Spaces, hyphens

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

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: with a 2 digit numeric code we could code 10 x 10= 100 locations. In contrast, with a 2 character alphanumeric code which uses 30 different characters, one has 30 x 30= 900 permutations.

The independent nations using alphanumeric postal code systems are:
 * Argentina (see table)
 * Brunei (see table)
 * Canada (see table)
 * Jamaica (see postal codes in Jamaica)(suspended in 2007 )
 * Malta (see table)
 * Netherlands (see table)
 * Peru
 * Somalia
 * Swaziland
 * United Kingdom (see table)
 * Venezuela (look up at http://www.ipostel.gob.ve/nlinea/codigo_postal.php).

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 to be used in conjunction with postal codes starting in 1994, but they have not become widely used. The European Committee for Standardization recommends use of ISO Alpha-2 codes for international postcodes and a UPU guide on international addressing states that "administrations may recommend" the use of ISO Alpha-2 codes.

Andorra, Azerbaijan, Barbados, Ecuador 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 those of 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 Belarus, Japan, Kyrgyzstan, Turkmenistan and Ukraine, 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.

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 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.

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 the International School of The Hague.

USA
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.

UK
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 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 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 BS 7666:

A9 9AA A9A 9AA A99 9AA AA9 9AA AA9A 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 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:
 * British Antarctic Territory: BIQQ 1ZZ
 * British Indian Ocean Territory: BBND 1ZZ, ISO code: IO
 * Falkland Islands: FIQQ 1ZZ, ISO code: FK
 * Gibraltar: GX11 1AA, ISO code: GI
 * Pitcairn Islands: PCRN 1ZZ, ISO code: PN
 * Saint Helena, Ascension and Tristan da Cunha:
 * Ascension Island: ASCN 1ZZ, ISO code: AC
 * Saint Helena STHL 1ZZ, ISO code: SH
 * Tristan da Cunha: TDCU 1ZZ, ISO code: SH (same as Saint Helena)
 * South Georgia and the South Sandwich Islands: SIQQ 1ZZ, ISO code: GS
 * Turks and Caicos Islands: TKCA 1ZZ, ISO code: TC
 * Anguilla: AI-NNNN
 * Bermuda: AA NN or AA AA, ISO code BM not used
 * British Virgin Islands: VGNNNN
 * Cayman Islands: KYN-NNNN*

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


 * SANTA CLAUS
 * NORTH POLE H0H 0H0

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

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.
 * 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.

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