Can I take a side job or start a second company while on Start-up Denmark?

A Start-up Denmark permit authorises you to work only in the specific innovative business approved by the expert panel. You cannot take an unrelated salaried job, and starting a different company is not covered. If you want to take additional employment or pivot to a new venture, you must apply for a separate residence and work permit on the appropriate basis. The permit also does not give you the right to work in other Schengen countries.