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. As of February 2025, 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 codice di avviamento postale ('postal expedition code'). CEP: The standard term in Brazil; CEP is an acronym for código de endereçamento postal ('postal addressing code'). Eircode: The standard term in Ireland, the first "official house-number scale" postal code. NPA in French-speaking Switzerland (numéro postal d'acheminement) and Italian-speaking Switzerland (numero postale di avviamento). 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 Postleitzahl ('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 Poštové smerovacie číslo (in Slovak) or 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
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" (Schutzstaffel), "SD" (Sicherheitsdienst), and "SA" (Sturmabteilung) 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.
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