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POSTCODE FACT

Did you know that even Father Christmas has his own postcode - SAN TA1. Letters sent to this postcode DO arrive!
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POSTCODE FACT

The combination of characters means that there are approximately 27 million postcodes in operation.
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POSTCODE FACT

Postcode data isn't free - Royal Mail licences use of the postcode database for a charge of around £4000 per year!

What are postcodes?

In the UK all addresses are given address identities, known as 'postcodes'. Introduced by the Royal Mail back in 1959, postcodes consist of between six and eight alphanumeric characters to identify where a particular address is.

Originally, these postcodes would help a Post Office employee to recognise which bin to sort a letter into, which enabled them to process mail quicker and more efficiently.

By 1965 the process had been perfected, and the original trial, which started in Norwich, was rolled out to the remainder of the country over the following years, costing £24 million, and by 1971 households were informed of their new postcode with franked mail, stating to 'Remember to use the Postcode'.

Each postcode consists of both an 'outward' and an 'inward' part, split into two with a single space separating these two parts.

Although postcodes were originally designed to assist in automating the sorting of mail to areas of the UK, they are also used for many different purposes.

Postcode Formats

Format Example Coverage
A9 9AA S1 1AA B, E, G, L, M, N, S, W postcode areas
A99 9AA M60 1NW
AA9 9AA CR2 6XH All postcode areas except B, E, G, L, M, N, S, W, WC
AA99 9AA DN55 1PT
A9A 9AA W1A 1HQ E1W, N1C, N1P, W1 postcode districts
AA9A 9AA EC1M 1BB WC postcode area; EC1-EC4, NW1W, SE1P, SW1 postcode districts

Postcode formats

Each postcode follows a set hierarchical format, with the first 2-4 characters representing the postcode area, i.e. the largest geographical unit available, followed by a number from 0-99, which determines which postcode district within the geographical area.

The second half of the postcode (the outward code), is generally followed by a space, then three characters - the first being a digit between 0-9 which determines the postcode sector, then the postcode unit, restricted to character from the set ABDEFGHJLNPQRSTUWXYZ. This excludes the characters CIKMOV so that there is no confusion between similar characters when postcodes are hand-written.

The combination of characters means that there are approximately 27 million postcodes in operation.

Exceptions to rules

There are several exceptions to the format of postcodes - some addresses are only used for routing, and are not suitable for either navigation or distance-finding services, so some postcode sectors were introduced that apply to non-geographic postcodes. These include:

  • EC50
  • BS98
  • BT58
  • IM99
  • N1P
  • NE99
  • SW99
  • GIR0AA