4 Nov 2009

UK Postcode Validation using C# Regular Expression

Sigh - look up UK Postcode Validation and you'll get about a billion different RegEx patterns, all subtly different and wrong.

The following one works because I use the official UK Postcode rules as defined by the government here.
public static bool ValidateUkPostcode(string postcode)
return Regex.Match(postcode, "(^gir\\s?0aa$)|(^[a-z-[qvx]](\\d{1,2}|[a-hk-y]\\d{1,2}|\\d[a-hjks-uw]|[a-hk-y]\\d[abehmnprv-y])\\s?\\d[a-z-[cikmov]]{2}$)", RegexOptions.IgnoreCase).Success;
NOTE: This solution requires you to include the Regular Expressions namespace at the top of your code:
using System.Text.RegularExpressions;
PS. Wondering why the regex allows "GIR 0AA"? For some reason Girobank were allowed their own non-conformant postcode. There's also "SAN TA1" for kids xmas posts, but that's just silly!!


  1. Anonymous5:26 pm

    Dude, do these support all those weird new london postcodes which have an extra character in the middle

  2. Anonymous10:06 am

    It's Working

  3. Acording to http://www.doogal.co.uk/files/postcodes.zip, there are 556 codes that doesn't match your regular expression.

    1. Thanks for the heads-up. Before I go to the trouble of setting up a test rig, can you give me an example of a code that fails the regex?

  4. Great work, saved me a load of time (regex scares me, was gonna do it the old fashioned way).

  5. You have provided very good information, and it is very useful.
    Thank you so much for this information.


  6. Superb kind of work by the author as on this particular topic people needs more precise information and special attention to it.Thanks a lot.
    mumbai pincode


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