When a client is "non-EU" for VAT purposes
For EU VAT purposes, a "non-EU client" is any business or individual established outside the 27 EU member states. This includes the United Kingdom (since Brexit), the United States, Switzerland, Norway, Canada, Australia, and every other country not in the EU.
The key distinction is where the client is established — their registered business address or, for individuals, their usual place of residence. A German freelancer invoicing a company headquartered in New York is invoicing a non-EU client. The same applies to a Dutch consultant working for a London-based firm — post-Brexit, the UK is a non-EU country for VAT purposes.
Note that some countries have special relationships with the EU that do not change their non-EU status for VAT. Switzerland has bilateral agreements with the EU but is not part of the EU VAT system. Norway and Iceland are in the EEA but not in the EU, and EU VAT rules do not apply to transactions with businesses in these countries. For VAT purposes, they are all non-EU.
Northern Ireland is a special case. Under the Windsor Framework, Northern Ireland follows EU VAT rules for goods but not for services. For services supplied by an EU business, Northern Ireland clients are treated as non-EU (UK rules apply).