Citizens from the Nordic countries
Citizens from the Nordic countries (Finland, Iceland, Norway, and Sweden) may enter Denmark without any restriction to reside, study, or work. You do neither need a residence permit nor a registration certificate. However, you must register your address in the Civil Registration System (CPR) and get a CPR number, a health insurance card, and a tax card.
Citizens from EU, EEA, and Switzerland
Citizens from the European Union (EU), the European Economic Area (EEA), and Switzerland are entitled to live and work in Denmark, but if you intend to reside in Denmark for more than three months, you must apply for a registration certificate at the International Citizen Service upon your arrival to Denmark. Then you must get a Civil Registration number (CPR number), a health insurance card, and a tax card.
Citizens from other countries
If you are a citizen from a country outside the Nordic countries, EU, EEA, or Switzerland, you must apply for a residence and work permit before your enter Denmark. Whether you can obtain a residence and work permit depends, first and foremost, on your qualifications.
If you already legally reside in Denmark, you can submit your application for a residence and work permit on newtodenmark.dk, at a Danish police station, or in the Citizen Center of the Danish Agency for International Recruitment and Integration.
The application process for a residence and work permit in Denmark is usually one to three months.
You will also need to get a Civil Registration number (CPR number), a health insurance card, and a tax card. Be aware that the rules will also apply when conducting voluntary/unpaid work.