For companies who deal with users in the United Kingdom, this reference guide can help you better understand how UK addresses are formatted and what makes an address valid.
The United Kingdom: Three Nations, One Province, 29 Million Addresses
The United Kingdom of Great Britain and Northern Ireland – commonly referred to as Britain, the United Kingdom, or simply the UK – is made up of three nations and one province: England, Scotland, Wales, and Northern Ireland. There are approximately 29 million known deliverable addresses in the UK, with over five thousand addresses being added and removed monthly.
International Country Code
The International Organization for Standardization (ISO) published the ISO 3166 standard, officially known as Codes for the representation of names of countries and their subdivisions.
The ISO 3166 standard consists of three parts:
| Part 1: ISO 3166-1 |
Country Codes – defines codes for the names of countries, dependent territories, and special areas of geographical interest. |
| Part 2: ISO 3166-2 |
Country subdivision code – defines codes for the names of primary subdivisions of a country, such as a state or a province. |
| Part 3: ISO 3166-3 |
Code for formerly used names of countries – defines codes for country names that have been removed from ISO 3166-1. |
ISO 3166-1, which defines country codes, contains three sets of country codes:
| ISO 3166-1 alpha-2: | Defines a country as a two-letter country code, commonly referred to as the ISO, ISO2, or ISO-2. |
| ISO 3166-1 alpha-3: | Defines a country as a three-letter country code, commonly referred to as numeric-3, ISO3, or ISO-3. |
ISO 3166-1 Country Codes – United Kingdom
| ISO 3166-1 alpha-2 code | ISO 3166-1 alpha-3 code | ISO 3166-1 numeric code |
| GB | GBR | 826 |
Note that the alpha-2 code is GB and not the UK.
ISO 3166-2 Country Codes
In the ISO, England, Scotland, Wales, and Northern Ireland are not included in the ISO 3166-1 country list and are instead listed as subdivisions of GB in ISO 3166-2. However, their subdivision description is that of “country,” except for Northern Ireland, which is described as a “province.”
| ISO 3166-2 code | Subdivision Name | Subdivision category |
| GB-ENG | England | Country |
| GB-SCT | Scotland | Country |
| GB-WLS | Wales | Country |
| GB-NIR | Northern Ireland | Province |
UK vs. GB Country Code – FIPS vs. ISO 3166-1
The United States Federal Government developed the Federal Information Processing Standards (FIPS) for use in computer systems by non-military government agencies and government contractors. Country codes are defined in the FIPS 10-4 standard, where the United Kingdom is listed as the UK and not GB. However, where the FIPS 10-4 codes where defined for use in computer systems, the standard has been dropped by many institutes and agencies in preference to ISO 3166-1, making ISO 3166-1 alpha-2 the global standard.
Postal Services
Mail in the United Kingdom is primarily handled by Royal Mail. Royal Mail was established in 1516 by King Henry the VIII, and it was government owned for 499 years. There are other mail delivery services available in the market, but many of them use Royal Mail for the last mile delivery.
Address Format
The address format for mail delivery in the United Kingdom is defined by Royal Mail, where an address is made up of four elements. The elements should appear in the following order:
| Address Element: | Address Example: | Element Names: |
| Premise | Royal Mail Flat 9, Wheatstone House |
[Organization] [Sub-Building], [Building Name] [Building Number]* |
| Thoroughfare | 47* Gorse View School Road |
[Dependent Thoroughfare] [Thoroughfare] |
| Locality | Southampton Knodishall Saxmundham |
[Double Dependent Locality] [Dependent Locality] [Post Town] |
| Postcode | SWA1AA | [Postcode] |
*NOTE: Although the building number appears with the thoroughfare, it is part of the Premise element.
Premise Elements
A mailing address premise is made up of the following elements:
| Order | Premise Element Name | Description | Example |
| 1 | Organization | The name of the organization, and when necessary the name of the department within the organization, which is registered to the delivery address. | Royal Mail |
| 2 | Sub-Building | This is also known as a sub-premise, such as an apartment, flat, or suite. | Flat 9 |
| 3 | Building Name | The name of the building of the business or residence. | Wheatstone House |
| 4 | Building Number | Also known as the premise number or address number, this number identifies the premise on the thoroughfare or dependent thoroughfare. | 47 |
Not all elements are required, but enough must be given to identify a single unambiguous delivery point. Also, note that while the building number is a part of the premise element, it must be applied on the same line as its corresponding thoroughfare.
Thoroughfare Elements
A thoroughfare premise is made up of the following elements:
| Order | Thoroughfare Element Name | Description | Example |
| 1 | Dependent Thoroughfare | Distinguishes a premise when a thoroughfare appears more than once in a post town. | Gorse View |
| 2 | Thoroughfare | This is also known as the street or road. | School Road |
Royal Mail defines three thoroughfare address possibilities:
- Thoroughfare without a dependent thoroughfare – When an address does not include a dependent thoroughfare, the element is to be omitted.
- Thoroughfare with a dependent thoroughfare – When an address contains both elements, Royal Mail instructs that the dependent thoroughfare is required and the thoroughfare is optional.
- No Thoroughfare – Not all addresses contain a thoroughfare, in which case the thoroughfare element is simply omitted.
Example:
Her Majesty the Queen
Buckingham Palace
London
SW1A 1AA
Locality Elements
The mail address Locality is made up of the following elements:
| Order | Locality Element Name | Description | Example |
| 1 | Double Dependent Locality | Distinguishes a premise when an address thoroughfare appears more than once in the same post town and dependent Locality. | Southampton |
| 2 | Dependent Locality | Distinguishes a premise when an address thoroughfare appears more than once in the same post town. | Knodishall |
| 3 | Post Town | Also known as the Locality; however, the post town represents the postal delivery Locality and not necessarily the geographic Locality. | Saxmundham |
Other aspects of Locality elements you should be aware of:
1. The Post Town is required.
2. The initial letter of the Post Town must always be capitalized.
3. The Post Town may be written in all capital letters (uppercase). It is the only Locality element where this is allowed.
Postcode
The postcode is made up of the following elements:
| Order | Element Name | Description | Example |
| 1 | Postcode | Also known as a postal code, this is an alpha-numeric code that is associated with one or more addresses along one or more thoroughfares. | SW1A 1AA |
The postcode must be written in all capital letters (uppercase) and must be the last address element. Royal Mail recommends that the postcode be listed as a singular element on the last line of the address; however, it may be preceded by either the county or post town on the same address line when separated by a space or on the preceding line.
Regarding County
Though the geographic county of an address is not required, according to the Royal Mail website regarding the inclusion of county, “you are welcome to do so.” However, the issue of listing geographic counties and postal counties has been the cause of some confusion over the years. Counties were removed from the address elements in the early 2000s, and they are no longer officially supported. This was due, in some part, to the boundaries of postal counties and geographic counties not matching up, so an address in one geographic county would be listed in a postal county of a different name.
Postcode Overview
The postcode is an alphanumeric code of varying length that is composed of two codes called the outward code and inward code. It ranges from six to eight characters in length with a single space to separate the two codes. A postcode may represent a group of addresses on a street or on a part of a street, a group of premises, or a single premise. On rare occasions, it may also represent a group of addresses on more than one street.
Postcode Format
Outward code
1. Postcode area
2. Postcode district
Inward Code
1. Postcode sector
2. Postcode unit
For example, in the postcode “SW1A 1AA” we have the following:
| Name | Example |
| Postcode | SW1A 1AA |
| Outward code | SW1A |
| Postcode area | SW |
| Postcode district | SW1A |
| Inward code | 1AA |
| Postcode sector | SW1A 1 |
| Postcode unit | AA |
Outward Code
The outward code represents the first half of the postcode that precedes the single space separator. It is made up of the postcode area and postcode district. The length of the outward code is between two and four characters.
Postcode Area
The postcode area is an alpha code that is one or two characters in length. The code commonly represents a geographical area. For example, “SW” represents London, “AB” is commonly Aberdeenshire, “BS” is often Avon, and so on.
Postcode District
The postcode district is the postcode area plus an alphanumeric code, essentially making it the outward code.
Inward Code
The inward code represents the second half of the postcode, immediately following the single space separator in the middle. It is three characters in length. The inward code is used to assist in the delivery of mail within a district.
Postcode Sector
The postcode sector is between four and six characters in length. It begins with the outward code, followed by the single space separator, and ends with the first digit of the inward code.
Postcode Unit
The postcode unit is an alpha code that is two characters in length. In addition to representing a group of addresses, the postcode unit may also represent a unique premise, an individual organization, or even a subsection/department of an organization. Postcode unit level designation cannot be purchased; it is determined by the amount of mail received by the premises or organization.
Special Postcodes
Royal Mail will assign postcodes to some high-profile organizations such as banks and telecoms, as well as non-geographic postcodes for assignment to PO Boxes and direct marketing. It will also assign postcodes to crown dependencies, overseas territories, and HM British Forces.
Crown dependencies
The crown dependencies are three self-governing island territories off the coast of Britain for which the United Kingdom is responsible. However, they are not a part of the United Kingdom or its territories. These islands have adopted the UK postcode format.
| Name | Postcode area |
| Guernsey | GY |
| Jersey | JE |
| Isle of Man | IM |
Overseas Territories
There are 14 overseas territories in the United Kingdom. They may be commonly referred to as British Overseas Territories or the United Kingdom Overseas Territories. These territories are mostly self-governed, and some have developed their own postal codes, such as Bermuda, the Cayman Islands, the British Virgin Islands, and Montserrat.
British Forces Post Office
The British Forces Post Office (BFPO) and Royal Mail use the non-geographic postcode area “BF” to represent a BFPO address.
Address Validation International: Overcoming Cultural Idiosyncrasies and Postal Format Variables
The above content provides a general overview of addresses in the United Kingdom. Understanding all the ins-and-outs of UK addresses can be a monumental task on its own. In addition, the ever-changing list of addresses, postcodes, and regulatory boundaries involved can make for a very dizzying array of challenges. Fortunately, the DOTS Address Validation International real-time service is capable and robust enough to handle various address formats and cultural idiosyncrasies. As always, our experienced staff is here to help, so please do not hesitate to reach out to us! We would be happy to answer any follow-up questions you may have and make recommendations on how to interpret and use the results from the service.
