Q: How should I abbreviate Counties of Great Britain & Northern Ireland?

A: Please use the Chapman Code.

There is a well established set of codes used within British & Irish Genealogy for abbreviating Counties in the United Kingdom of Great Britain and Northern Ireland and also the Counties of Ireland. You are strong encouraged to adopt them as tags on content relating to the British Isles within this site.

If you are not familiar with the Chapman Codes you'll find a complete listing on genuki.org.uk and on Wikipedia

Chapman Country Codes

Chapman also defines six country codes namely

 CHI     Channel Islands
 ENG     England
 IOM     Isle of Man
 IRL     Ireland
 SCT     Scotland
 WLS     Wales

ISO 3166-1 Country Code GB

Please also note that the ISO-3166 Country code for the United Kingdom of Great Britain and Northern Ireland is GB. Whilst GB is the preferred folksonomy tag, UK (which is reserved by the United Kingdom on the ISO-3166 list) is acceptable within the project Wiki. Just remember to include both in any search.