If taking up residence in Denmark, an imported vehicle must be registered within 30 days of arrival, or within 30 days of obtaining your CPR (personal identification) number; failure to do so will incur a hefty fine.
The registration form for importing a foreign registered vehicle is only available in Danish, so it is important that you enlist the help of a Danish speaker if you do not speak the language.
In order to register a car and receive Danish number plates, the vehicle must undergo an inspection and registration tax must be paid; this is calculated by SKAT (the Danish tax authority) based on the valuation of the vehicle. You will also have to pay around DKK 2,000 for a set of number plates.
It is also possible to drive a foreign registered car in Denmark without having to register it, however, this is only applicable if you are staying in the country temporarily.
For further information and a list of authorised inspection centres consult the official SKAT website.