Why can I no longer enter the country code of EU?

The UK authorities have now implemented validation to stop users entering the country code of "EU" on customs declarations.

The country code of "EU" will be invalid on CHIEF from 01/01/2022 and CDS shortly after that date.

• When creating import or export declarations, ensure that the actual member state's country code is entered.
  
  If data is transferred from an ERP system, ensure that the appropriate codes are updated accordingly.
  
  If templates are being used to populate any country code field, it would be necessary to update the template information too.