List of postcode areas in the United Kingdom

This is a list of postcode areas, used by Royal Mail for the purposes of directing mail within the United Kingdom. The postcode area is the largest geographical unit used and forms the initial characters of the alphanumeric UK postcode. There are currently 121 geographic postcode areas in use in the UK and a further three often combined with these covering the Crown Dependencies of Guernsey, Jersey and Isle of Man.
Each postcode area is further divided into post towns and postcode districts. There are on average 20 postcode districts to a postcode area, with ZE having the lowest (3) and BT the highest (81). The London post town is instead divided into several postcode areas.
The single or pair of letters chosen for postcode areas are generally intended as a mnemonic for the places served. Postcode areas, post towns and postcode districts do not follow political or local authority administrative boundaries and usually serve much larger areas than the place names with which they are associated. Many post towns are former "county towns" but postcode areas rarely align with the county (or successor authority) area. For example, within the PA postcode area the PA1 and PA78 postcode districts are 140 miles (225 km) apart, and cover 5 local authority areas; and the eight postcode areas of the London post town cover only 40% of Greater London. The remainder of its area is covered by sections of twelve adjoining postcode areas: EN, IG, RM, DA, BR, TN, CR, SM, KT, TW, HA and UB.
The Crown dependencies (which are not part of the United Kingdom) did not introduce postcodes until later, but use a similar coding scheme. They are separate postal authorities.
Glasgow, like London, was divided into compass districts: C, W, NW, N, E, SE, S, SW. When postcodes were introduced, these were mapped into the new G postcode: C1 became G1, W1 became G11, N1 became G21, E1 became G31, S1 became G41, SW1 became G51, and so on. As NW and SE had never been subdivided they became G20 and G40 respectively.
Norwich and Croydon were used for a postcode experiment in the late 1960s, which was replaced by the current system. The format was of the form NOR or CRO followed by two numbers and a letter, e.g. NOR 07A. They were later changed to CR0 (digit '0') and NR1.
When Ireland was a part of the United Kingdom of Great Britain and Ireland a postal district system was introduced in 1917 by the UK government. The letter D was assigned to Dublin. Upon the establishment of the Irish Free State and later, the Republic of Ireland, the Irish government retained the designation and today it forms part of the Eircode system, a postcode format slightly different from the UK format and identifying individual addresses. Since Irish independence, D has never been reassigned as a postcode area in the UK.
Some postcode areas do not correspond to geographical areas. They can be - (a) postcode areas with no geographic link (for use by Large Volume Receivers ("bulk mail", with delivery options determined between the LVR and Royal Mail) and these can for general mail or specific functions (e.g. parcel returns; centralised scanning of mail); (b) non-geographic postcode districts or sectors contained within geographic postcode areas (for LVRs or PO Boxes); and (c) specific purpose postcodes.
For those within geographic postcode areas, the first two numbers can be any number though they are generally larger than the numbers allocated to geographic districts. Some fall within the range 91 to 99 (e.g. S98 for payments to MNBA Ltd; NE98 for Department for Work and Pensions, Central Office, Newcastle-upon-Tyne). However, there are many exceptions to this - e.g. American Express has the postcode area BN88; in Glasgow G58 1SB is allocated to National Savings, formerly National Savings Bank, as a mnemonic (SB, and with 58 looking like SB), though it is located in the G43 postcode district; and in Glasgow G70 is allocated to HMRC which is located in G67. Some are in fact geographic e.g. EH99 1SP for the Scottish Parliament in Edinburgh.
The BF postcode area was introduced in 2012 to provide optional postcodes for British Forces Post Office addresses, for consistency with the layout of other UK addresses. It uses the national non-geographic post town "BFPO" and, as of 2012, the postcode district "BF1". Each BFPO number is assigned an inward code, which are grouped as: 0 - Germany, 1 - UK, 2 - Rest of Europe, 3 - Rest of World, 4 - Ships and Naval Parties, 5 - Rest of World, Operations and Exercises, 6 - Rest of World, Operations and Exercises.
The non-geographic postcode area BX has been introduced for addresses which do not include a locality; this allows large organisations long-term flexibility as to where they receive their mail. This postcode area is used by Lloyds Banking Group (BX1 1LT), HSBC (BX8 0HB) and parts of HM Revenue and Customs like VAT (BX5 5AT) and Pay As You Earn (BX9 1AS). Lloyds Bank also use BX4. After splitting from Lloyds, TSB Bank uses BX4 7SB, the latter part of which, when written, looks similar to "TSB".
GIR 0AA is a postcode created for Girobank in Bootle. It remained in use by its successors when Girobank was taken over by Alliance & Leicester and subsequently by Santander UK.
XM4 5HQ is a postcode created for letters sent to Santa Claus or Father Christmas (with XM4 5HQ resembling "XMAS").
The non-geographic postcode area XX is used by online retailers for returns by Royal Mail, and was used for COVID-19 test samples.
Certain British Overseas Territories introduced single postal codes for their territory or major sub-sections of it. These are not UK postcodes, even though many are formatted in a similar fashion:
Other overseas territories have introduced their own more extensive postcode systems:
Civilian residential and business addresses in Akrotiri and Dhekelia are served by Cyprus Postal Services and use Cypriot postal codes.
Mail to Overseas Territories is treated as international if posted in the UK.