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 digits or both, sometimes including spaces or punctuation, included in a postal address for the purpose of sorting mail.
the Universal Postal Union lists 192 countries which require the use of a postal code.
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: CAP: The standard term in Italy; CAP is an acronym for ('postal expedition code'). CEP: The standard term in Brazil; CEP is an acronym for ('postal addressing code'). Eircode: The standard term in Ireland, the first "official house-number scale" postal code. NPA in French-speaking Switzerland () and Italian-speaking Switzerland (). 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 ('postal routing number'). Postal code: The general term is used in Canada. Postcode: This 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. PSČ: The standard term in Slovakia and the Czech Republic; PSČ is an acronym for (in Slovak) or (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
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) 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, but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941, followed by Singapore in 1950, 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 it was not used nationwide until 1974.
Presentation
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" (), "SD" (), and "SA" () are not used, due to links with the 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.
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 (see table) Brunei (see table) Canada (see table) Eswatini Ireland (see table) Jamaica (see table) (suspended in 2007) Kazakhstan (since 2015) Malta (see table) Netherlands (see table) 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 (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, 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 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 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 divisions.
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 Territorial Division, and continue to be equivalent.
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 boundaries
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, 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), 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 8-digit postcodes are an evolution of the five-digit area postal codes. In the 1990s the Brazilian five-digit postal code (illustrated), DDDDD, received a three-digit suffix DDDDD-SSS, but this suffix is not directly related to the administrative district hierarchy. The suffix was created only for logistic reasons.
The postal code assignment can be assigned to individual land lots 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 The number of digits and the alphabet of the digit (decimal with 10 characters or alphanumeric with 36 characters) is proportional to the amount of information; so when used correctly, it provides geographical precision.
It is necessary to establish an important distinction between technological solutions: