Non EU citizens who stay in Italy for less than 90 days for study, research, tourism, business or visit purposes may be required to declare their presence.
For short stay it is not requested to apply for a residence permit.
If you travel from a Schengen State and you stay by family members, relatives or friends, you must report your presence within 8 days after you have entered Italy by submitting the Dichiarazione di presenza form (Declaration of presence) and cessione fabbricato to the local Police headquarter (Questura).
When is it not required?
When you stay in a hotel since there is a registration form you are asked to sign upon arrival. Please keep this always with you and show it to any police officer who should request it.
When you travel from a Non-Schengen State since the stamp that the border authorities put on your travel documents attests your presence.
The Declaration is asked for family reunion when the request is processed in Italy (ricongiungimento in sede).