Format/length: an8 (max)
HES item:
National Codes:
Default Codes:

UK Government Data Standards Catalogue (GDSC), Version 2.1, Agreed 01.09.02. GDSC:

POSTCODE is the same as attribute POSTCODE.

UK Government Data Standards Catalogue

Data Element Post Code
Is Part Of
BS7666 Address
Has Parts  
Version 2.1
Status Release
Previous Versions
Version: 2.0 Status: Release
Later Versions  
Date Agreed 1 September 2002

Meta Data Value
Name Post Code
Description The code allocated by the Post Office to identify a group of postal delivery points.
Business Format Max 8 characters.
Element Type Data Type
Format Example Postcode

Please note the following:-

  • The letters Q, V and X are not used in the first position.
  • The letters I, J and Z are not used in the second position.
  • The only letters to appear in the third position are A, B, C, D, E, F, G, H, J, K, S, T, U and W.
  • The only letters to appear in the fourth position are A, B, E, H, M, N, P, R, V, W, X and Y.
  • The second half of the Postcode is always consistent numeric, alpha, alpha format and the letters C, I, K, M, O and V are never used.

These conventions may change in the future if operationally required.

*GIR 0AA is a Postcode that was issued historically and does not confirm to current rules on valid Postcode formats, It is however, still in use.

Default Value
Owner Royal Mail
Based On Royal Mail
1. The Postcode is a combination of between five and seven letters / numbers which define four different levels of geographic unit. It is part of a coding system created and used by the Royal Mail across the United Kingdom for the sorting of mail. The Postcodes are an abbreviated form of address which enable a group of delivery points (a delivery point being a property or a post box) to be specifically identified. There are two types of Postcode, these being large and small user Postcodes.

A large user Postcode is one that has been assigned to a single address due to the large volume of mail received at that address.

A small user Postcode identifies a group of delivery points. On average there are 15 delivery points per Postcode, however this can vary between 1 and 100.

Each Postcode consists of two parts. The first part is the Outward Postcode, or Outcode. This is separated by a single space from the second part which is the Inward Postcode, or Incode.The Outward Postcode enables mail to be sent to the correct local area for delivery. This part of the code contains the area and the district to which the mail is to be delivered.The Inward Postcode is used to sort the mail at the local area delivery office. It consists of a numeric character followed by two alphabetic characters. The numeric character identifies the sector within the postal district. The alphabetic characters then define one or more properties within the sector.

The following characters are never used in the inward part of the Postcode:C I K M O V.

An example Postcode is PO1 3AX. PO refers to the Postcode Area of Portsmouth. There are 124 Postcode Areas in the UK. PO1 refers to a Postcode District within the Postcode Area of Portsmouth. There are approximately 2900 Postcode Districts. PO1 3 refers to the Postcode Sector. There are approximately 9,650 Postcode Sectors. The AX completes the Postcode. The last two letters define the 'Unit Postcode' which identifies one or more small user delivery points or an individual Large User. There are approximately 1.71 million Unit Postcodes in the UK.

2. The schema is to be updated to match this definition.

This data element is also known by these names:

Context Alias