Editing Postal code (section)

==== United Kingdom ====
{{More citations needed section|date=January 2025}}
{{Further|Postcodes in the United Kingdom}}
For domestic properties, an individual postcode may cover up to 100 properties in contiguous proximity (e.g. a short section of a populous road, or a group of less populous neighbouring roads). The postcode together with the number or name of a property is not always unique, particularly in rural areas. For example, GL20 8NX/1 might refer to either 1 Frampton Cottages or 1 Frampton Farm Cottages, roughly a quarter of a mile (400 metres) apart.

The structure is alphanumeric, with the following six valid formats, as defined by [[British Standards|BS]] 7666:<ref>{{cite web |title=BS7666 Address |work=Data Standards Catalogue |publisher=UK National Archives |date=2 October 2009 |url=http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |archive-url=http://webarchive.nationalarchives.gov.uk/20130128101412/http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |url-status=dead |archive-date=28 January 2013 |access-date=15 August 2015 }}</ref>

   AN NAA
  ANA NAA
  ANN NAA
  AAN NAA
 AANA NAA
 AANN NAA

There are always two halves: the separation between outward and inward postcodes is indicated by one space.

The outward postcode covers a unique area and has two parts which may in total be two, three or four characters in length. A postcode area of one or two letters, followed by one or two digits, followed in some parts of London by a letter.

The outward postcode and the leading numeric of the inward postcode in combination forms a postal sector, and this usually corresponds to a couple of thousand properties.

Larger businesses and isolated properties such as farms may have a unique postcode. Extremely large organisations such as larger government offices or bank headquarters may have multiple postcodes for different departments.

There are 121 postcode areas in the UK, ranging widely in size from [[BT postcode area|BT]] which covers the whole of Northern Ireland to [[WC postcode area|WC]] for a small part of [[Central London]]. Postcode areas occasionally cross national boundaries, such as [[SY postcode area|SY]] which covers a large, predominantly rural area from [[Shrewsbury]] and [[Ludlow]] in [[Shropshire]], England, through to the seaside town of [[Aberystwyth]], [[Ceredigion]] on [[Wales]]' west coast.  There are a number of special purpose postcode areas that are "non-geographic" and which provide special routing instructions (such as parcel returns to online retailers).  The three Crown dependencies and Gibraltar also use UK formatted postcodes.  Some British Overseas Territories have adopted a single postcode for their territory that is very similar to the UK format.