...

...

Countries

Based on the ISO Code List

https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2

There are also some special codes through HMRC for Isle of Man, Jersey, Guernsey

Also see https://www.uktradeinfo.com/CodesAndGuides/Pages/CodesGuides.aspx

...

Currencies

Based on ISO 4217 - https://en.wikipedia.org/wiki/ISO_4217

Also See https://www.uktradeinfo.com/CodesAndGuides/Pages/CodesGuides.aspx

...

Trade Terms

The trade terms are codes issued by HMRC which are used to define INCOTerms

IncoTerms are explained on this wiki https://en.wikipedia.org/wiki/Incoterms

Also see https://www.uktradeinfo.com/CodesAndGuides/Pages/CodesGuides.asp