Postcodes in the United Kingdom

Postal codes used in the United Kingdom, British Overseas Territories and Crown dependencies are known as postcodes (originally, postal codes). They are alphanumeric (the UK is one of only 11 countries or territories to use alphanumeric codes out of the 160 postcode using members of the ICU) and were adopted nationally between 11 October 1959 and 1974, having been devised by the General Post Office (Royal Mail).

The system was designed to aid in sorting mail for delivery. It uses alphanumeric codes to designate geographic areas. A full postcode identifies a group of addresses (typically around 10) 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.

The initial postcode system evolved from named postal districts introduced in London and other large cities from 1857. Districts in London were then subdivided in 1917, with each allocated a distinct number, which extended to other cities by 1934. The territory of the UK is broken down into 121 postcode areas.