United Kingdom Postal Code Format Guide
UK postcodes contain an outward code, a space, and a three-character inward code. Length varies, letters and digits are mixed, and the final format must preserve the space.
Standard format
A(A)N(A) NAA
Example
SW1A 1AA
Implementation and validation notes
UK postcodes contain an outward code, a space, and a three-character inward code. Length varies, letters and digits are mixed, and the final format must preserve the space.
Validate required state, character set, length, and syntax on the client, then repeat validation on the server. Preserve the original input and normalize into a separate field; never truncate local scripts, compound names, or leading zeroes to fit a single Western assumption.
This guide describes common formats rather than an official registry and cannot enumerate every exception. Generated output is for testing only, not delivery, calling, identity verification, or real account activity.
Related resources
Frequently asked questions
What is the standard United Kingdom postal code format?
A common representation is A(A)N(A) NAA, for example SW1A 1AA. UK postcodes contain an outward code, a space, and a three-character inward code. Length varies, letters and digits are mixed, and the final format must preserve the space.
How should United Kingdom postal code test data be stored?
Store the original value as a string so leading zeroes, spaces, hyphens, accents, and local scripts are preserved. Use a separate normalized field for search.
Does correct formatting prove the data is real?
No. Syntax validation cannot prove an address is deliverable, a number is assigned, or a name belongs to a real person.