Postal codes used in the United Kingdom, British Overseas Territories and Crown dependencies are known as postcodes (originally, postal codes).[1] They are alphanumeric and were adopted nationally between 11 October 1959 and 1974, having been devised by the General Post Office (Royal Mail).[2] The system uses alphanumeric codes to designate geographic areas. A full postcode, also known as a "postcode unit", identifies a group of addresses or a major delivery point. It consists of an outward code and inward code. The outward code indicates the area and district, while the inward code specifies the sector and delivery point, typically encompassing about 15 addresses.
Postcode areas are generally named after major towns or cities, such as B for Birmingham, although some are named after smaller towns or geographical features. London has eight postcode areas (N, E, EC, SE, SW, W, WC, and NW) instead of a single area, and Northern Ireland uses the BT area code for Belfast. The system aids in sorting mail and is used in various applications. They help calculate insurance premiums, designate destinations in route planning software, and serve as aggregation units in census enumeration. The Postcode Address File (PAF) database stores and updates the boundaries and address data for around 29 million addresses, ensuring accurate delivery and extensive utility beyond postal services.
The initial postcode system evolved from named postal districts introduced in London and other large cities from 1857. London was divided into numbered subdivisions in 1917, which extended to other cities by 1934. Each postcode area contains multiple post towns and districts. For example, the GU postcode area covers a significant part of southern England, with Guildford as a major town, and Woking as another post town within the GU22 district.
- ^ Royal Mail (October 2004). Address Management Guide (4 ed.). Royal Mail Group.
- ^ "A short history of the postcode". The Independent. 1 January 2005. Retrieved 3 October 2009.