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.

Germany was the first country to introduce a postal code system, in 1941. The United Kingdom followed in 1959 and the United States in 1963.

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

Usage conventions

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, whereas in most continental European countries it precedes the name of the city or town.

National prefixes

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. 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). Usage of ISO 3166-1 alpha-2 codes was recommended to be used starting in 1994, but did 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.

Alphanumeric postal codes

Most postal codes are numeric. The few independent nations using alphanumeric postal code systems (with letters and digits) are:

• Andorra
• Argentina
• Brunei
• Canada
• Jamaica
• Malta
• The Netherlands
• United Kingdom
• Venezuela

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.

Postal codes in particular countries

Algeria

In Algeria, the postal codes of province capitals are composed of the province code and three zeros, for example: 16000 for Algiers, while the postal codes of other cities, towns, and villages in the province are the provincial code followed by three numerals. See "list of postal codes of Algerian cities" for the postal codes of all of Algeria's 1,541 municipalities, and other places with their own postal code.

Argentina

The Argentine postal code is a system that assigns at least one unique alphanumeric postal code to each municipality. Some larger cities have several codes starting at a base code, and the codes of all municipalities with a population over 500 additionally show the side of the block where the address is located.

The CPA consists of three parts:

1. A single letter that encodes the province (for example, C for Capital Federal, Q for Neuquén).
2. Four digits (the old postal code or a variation of it on the last digits) showing the municipality.
3. Three letters, identifying a side of the block where the address is located.

Until 1998 Argentina employed a four-digit postal code for each municipality, with the first digit representing a region in the country, except in the case of the city of Buenos Aires. The CPA is intended to improve the quality and speed of mail delivery, but mail without a well-formed CPA will be delivered correctly as well.

Australia

Australian postcodes are numeric, consisting of four digits. They were introduced in 1967 by the Postmaster-General's Department (PMG), the predecessor of Australia Post. For a history of the PMG / Australia Post see here.

Postcodes are published in small booklets available from post offices, and also in the white pages of telephone directories.

On envelopes and postcards there are usually four rectangular boxes printed in orange ink at the bottom right for the postal code digits.

Austria

Austrian post codes were introduced in 1966 and consist of four numbers. The first indicates the state:

• 1xxx: Vienna
• 2xxx: Lower Austria (east of Vienna)
• 3xxx: Lower Austria (west of Vienna)
• 4xxx: Upper Austria
• 5xxx: Salzburg and east Upper Austria
• 6xxx: Tyrol and Vorarlberg (without East Tyrol)
• 7xxx: Burgenland
• 8xxx: Styria
• 9xxx: Carinthia and East Tyrol

The second number indicates the regional area in the state, the third number is for the routing allocation, following railways and post car routes and the fourth number indicates the post office. Every post office has its own number. There are some exceptions to this rule: In Vienna, the second and third numbers show the district, so 1120 would be the twelfth district. Also, some cities close to the German border in Vorarlberg have Austrian and German postcodes.

There are also some special post codes: the airport has its own post code (1300), the UN (1400) and some big companies also have their own post code, for example the ORF, the Austrian National Broadcasting Service (1136). These special post codes are not listed in the public phonebook, though there is a book which contains them and can be bought at an Austrian post office.

Belgium

Belgian post codes are numeric and consist of 4 numbers, although the last one is often zero. The first digit indicates the province (except for the 3xxx numbers that are shared by the eastern part of Flemish Brabant and Limburg and the and 1xxx that are shared by the Brussels Capital Region, the western part of Flemish Brabant and Walloon Brabant), the other numbers were given more or less at random. The more zeros though the higher the number of inhabitants of that city in the province. For example: Brugge is the capital and largest urban centre of the coastal province of West Flanders so it gets the 8000 code, the second city is Kortrijk and gets 8500. When writing the address, the postal code is put in front of the town name.

Special numbers are reserved for the EU institutions, NATO headquarters, public and commercial broadcasters (RTBF, RTL TVi, VRT and VTM), the different parliaments and other public institutions.

Brazil

Postcodes in Brazil follow a nationwide scheme known as CEP (Código de Endereçamento Postal) ( Postal Addressing Code ) introduced in 1972 as a sequence of five digits. To keep mail services up with economic growth, a three-digit suffix was added in 1992.

Most cities with population around 100,000 and above have a CEP assigned to every public place and to some high-occupancy private spaces, like major commercial buildings and large residential condos. Small towns are assigned a general code, usually with attributed town code followed by the suffix -000 .

Correios , Brazil's mail service, requests (but not requires) that the code be placed in the last line of the address and although totally unrequired (and even unwanted by automatic sorting machines) the acronym CEP is usually placed before the code, e.g. CEP 29145-586.

Valid examples for mailing in Brazil are:

Rua Governador Roberto Silveira, 108
Centro
Macaé- RJ
CEP 27910-050

or

Rua Remanso, 35
Tingui
Rio de Janeiro- RJ
CEP 23080-060

Any CEP code can be obtained from Correio's website, if you have a Flash plugin (in Portuguese).

Brunei

Postal codes used in Brunei are alphanumeric, consisting of two letters followed by four digits in the format of YZ0000, where Y denotes the district code, Z denotes the mukim code, the first two digits denote the area or village code, and the last two digits denote the nearest post office code (e.g. the postal code for Pantai Mentiri Golf Club is BU2529).

For a list of Brunei Postal Codes go to http://www.pos.gov.bn/postcode/images/Poskod1.htm

Bulgaria