In the new law on security there has been a change to tourist rental contracts for less than 30 days. There is now the requirement to notify the questura within 24 hours of the guests arrival of the guests particulars. This is for renters and subrenters, and is also for holiday homes. The requirement was already in place for non EU citizens and for those who rented for more than 1 month. From 4th December there is a more rigorous system of checks, and they are the same requirements as for hotels and other tourist structures. It is also valid for those who just rent out a room (such as AirBnB).
Within 24 hours of the rental starting (or immediately if the rental is for less than 24 hours), the guests must be registered on the Alloggiati Web site of the Police. The fines for not doing so are up to 206 euros or 3 months arrest.