How to read the result

Three answers go in: where the business is established, what it does with customs, and where the goods enter or leave. The result shows which kind of number the guidance points to, who issues it and why, with a link to the sentence's source. Where a source does not cover the case, the result says so and does not fill the gap.

The three kinds of number

Prefix	Issued by	The guidance points to it when	Source
An EU country code, for example FR or NL	The customs authority of one EU country	The business is established in the EU, or it is outside the EU and lodges declarations or acts as a carrier there	European Commission
XI	HMRC	The business is based in Northern Ireland, or it is outside Northern Ireland and the EU and needs a number for a limited customs activity there	HMRC, place of registration
GB	HMRC	The business is established in the UK, or it is outside the UK and needs one for an allowed limited customs activity in Great Britain	HMRC, place of registration

What the tool does not do

It does not decide. The customs authority of the country decides who is registered. The tool repeats published guidance.
It does not cover every case. Groups of companies, VAT groups, branches and unusual activities are outside the three questions. The Commission guidance and HMRC have separate sections on them: see where to register in the EU and the cases from the guidance.
It sends nothing. Your answers stay in your browser.

After the result

If the result points to a number, the next step is the registration route named at the bottom of the result. If you already hold a number, check its shape with the format checker and confirm it with the official services.

Not customs advice. A customs broker or the national customs authority can tell you what applies to your own activity.