In Denmark you are not allowed to try and control rats yourself. Instead you are obliged to report any sighting of rats to your municipality.
Incorrect use of poison can promote development of resistance in rats. Therefore you should leave rat control to the experts; authorised rat controllers.
If you see rats on your property there is no need to panic. Once the controller has ascertained that there are rats, has found the cause, and initiated control measures, it is usually just a question of time before they are gone.
Property owners have a duty to secure and clean their property to keep rats at bay. This applies to home owners, farmers and owners of rental properties.