The transitional agreement between the UK and the EU will end on 1 January next year, meaning operators headquartered in Great Britain will face different rules for offering online gambling in Denmark.
Licensees residing or established outside EU or European Economic Area (EEA) countries will only be permitted to offer online gambling in Denmark if they have appointed a representative.
Spillemyndigheden said it is the responsibility of the licence-holder to ensure that their representative is either resident or established in Denmark or another EU or EEA country.
As such, the regulator said GB-based operators that hold a licence in Denmark must now seek to work with a representative to continue to offer gambling in the country.
The new guidance comes after Spillemyndigheden last week revealed Denmark has the lowest gambling spend of any Nordic country and eighth lowest of 10 European nations sampled.
The average Danish adult spending DKK2,101 (£257/€283/$342) annually.