Employees from Bulgaria and Romania who have not held residence permits in Norway in the last 12 months are subject to different regulations than other EU/EEA/EFTA nationals. The transitional rules contain stricter requirements regarding employment relationships.
You can stay in Norway for three months before you need to apply for a permit, or six months if you are seeking employment. You can start working once you have submitted a complete application for a residence permit in Norway.
If you have had legal residence as an employee for the last 12 months, you can register under the registration system for EEA nationals.