If you are a Norwegian business enterprise and have dealings with the customs authorities in an EU country, you will need an EORI number. You will receive such a number by applying to the customs authorities in the relevant EU country.
The EORI number (Economic Operator Registration and Identification number) is a unique identity number (customer number) from the customs authorities in the EU. You must use this number for all customs-related business in the EU.
You can read more about EORI numbers on the website of the European Commission.
Check the validity of an EORI number: EORI number validation