Authorities use different identification numbers to identify companies and entities. Organisation numbers are used in Norway. The tax authorities in other countries use corresponding identification numbers to identify companies and entities in the same way. You must specify the company’s or entity's foreign identification number so that the tax authorities in the place where the company or entity is resident for tax purposes can link the account information to it.
For example, the tax authorities in Denmark use a CVR number, in Canada a Business Number (BN) is used, and in France numéro SIREN is used as an identification number.
Such identification numbers are often referred to as a TIN ("Taxpayer Identification Number"). Not all countries use such identification numbers. More information regarding the identification numbers used in various countries can be found here.