Visa holders who plan to move to Italy MUST apply for a Permesso di Soggiorno (Residence Permit) within 8 days after entering the country to the closest Questura (Police Department).
When requesting the Permesso di soggiorno, you may be asked to submit copies of the entire documentation submitted for the visa.
The residence permit is the document that legitimizes your stay in Italy beyond 90 days.
A residence permit is not required for business, tourism, short visits or study, provided that the stay does not exceed 3 months.