Laws regarding the offer of rental properties in Spain have been in place for a number of years. In reent times, the authorities has started to clamp down on this popular activity. Basically, if offering a property for rent, then you to comply with the rules and obtain a licence.
Failure to comply with the new laws regarding illegal tourist properties may result in substantial fines. This depends on how serious the infraction is. If someone is letting out an apartment for holidays without it being recorded in the registry. Then a sanctioning file is initiated. You could be charged many thousands of euros!
Also owners without a licence have to stop letting. You may also be breaching safety, health and hygiene regulations without realising. Which could result in more fines for you.
All property adverts MUST always display the tourist reference number.