Can I start right away? 

Yes, but legal requirements must be fulfilled. Foreign nationals and enterprises intending to operate a permanent business in Norway must comply with the same regulation as Norwegian enterprises.

More information
Altinn – Start and run business is the official website providing all the information you need to start and operate a business in Norway. This website has information on relevant topics, document templates, guides and forms you will need to be able to register and operate a business in Norway.