Postcodes in the United Kingdom

Postcodes help calculate insurance premiums, designate destinations in route planning software, and serve as aggregation units in census enumeration.

This is followed by a space and then the incode which indicates the postcode sector and delivery point (usually a group of around 10-15 addresses,[citation needed] but can vary).

Postcodes have been adopted for a wide range of purposes in addition to aiding the sorting of mail: for calculating insurance premiums, designating destinations in route planning software and as the lowest level of aggregation in census enumeration.

In 1923, Glasgow was divided in a similar way to London, with numbered districts preceded by a letter denoting the compass point (C, W, NW, N, E, S, SW, SE).

[4] In November 1934 the Post Office announced the introduction of numbered districts (short postal codes) in "every provincial town in the United Kingdom large enough to justify it".

A poster was fixed to every pillar box in the affected areas bearing the number of the district and appealing for the public's co-operation.

Businesses were issued with a free booklet containing maps and listings of the correct district number for every street in the ten areas.

Postcodes were suggested to increase the efficiency of this process by removing the need for the sorter to remember the correct sorting for as many places.

The envisaged format was a six-character alphanumeric code with three letters designating the geographical area and three numbers to identify the individual address.

[10] On 28 July Ernest Marples, the Postmaster General, announced that Norwich had been selected, and that each of the 150,000 private and business addresses would receive a code by October.

[12] In October 1965, Tony Benn as Postmaster General[13] announced that postal coding was to be extended to the rest of the country in the next few years.

Within two years it was expected that full coding would be used in Aberdeen, Belfast, Brighton, Bristol, Bromley, Cardiff, Coventry, Manchester, Newcastle upon Tyne, Newport, Reading, Sheffield, Southampton and the Western district of London.

That code no longer exists in the Royal Mail's PAF system, but was taken over by the bank's current owners, Santander UK.

The Office for National Statistics (ONS Geography) maintains and publishes a series of freely available, downloadable postcode products that link all current and terminated UK postcodes to a range of administrative, health, statistical and other geographies using the Code-Point Open grid reference.

The CEO of Guernsey Post, Boley Smillie, said "this has been a long time coming" and "... Sark should have had its own identity back then [when postcodes were adopted in 1993]".

[52] They are commonly termed “non-geographic” postcodes in the sense that they refer not to physical addresses but to specific recipients (who have made arrangements for the delivery of incoming mail).

"Non-geographic" postcodes are used for various purposes, many of which were introduced after, or have significantly evolved since, the introduction of the current post code system, including: Admail, "bulk mail" or large volumes (government and business), centralised scanning of inward mail, competitions, parcel returns, direct marketing and PO boxes.

Significant addressees: Some postcodes in the "non-geographic" range 90-99 are in fact geographic, but specific to the institution or entity and not part of the surrounding numbering sequence (and thus quite different from the neighbouring properties) - for example, EH99 1SP can be used with GPS mapping to locate and navigate to the Scottish Parliament (which is directly opposite the Palace of Holyrood House, EH8 8DX, and across the road from 7/4 Canongate, EH8 8BX).

[53] Prominent examples are: The postcode printed on Business Reply envelopes (which do not require a stamp) often ends with the letters BR.

[67] A variation of automated sorting uses optical character recognition (OCR) to read printed postcodes, best suited to mail that uses a standard layout and addressing format.

[68] A long string of "faced" letters (i.e. turned to allow the address to be read) is presented to a keyboard operator at a coding desk, who types the postcodes onto the envelopes in coloured phosphor dots.

The associated machine uses the outward codes in these dots to direct bundles of letters into the correct bags for specific delivery offices.

[25] This feature depends upon whether it is cost effective to second-sort outward letters, and tends to be used only at main sorting offices where high volumes are handled.

A newer system of five-digit codes called Mailsort was designed for users who send "a minimum of 4,000 letter-sized items".

[72] It encodes the outward part of the postcode in a way that is useful for mail routing, so that a particular range of Mailsort codes goes on a particular plane or lorry.

On its website, Royal Mail publishes summary information about major changes to postcode sectors and postal localities (including post towns).

A complete list of all current Great Britain postcodes, known as Code-Point Open, has been made available online (since 1 April 2010) by Ordnance Survey.

Unlike the PAF products provided by Royal Mail, the Code-Point Open list does not include postal address text.

The Office for National Statistics also produces postcode directories, under similar licence terms to the OS product.

This has led to British Sky Broadcasting subscribers receiving the wrong BBC and ITV regions, and newly licensed radio amateurs being given incorrect call signs.