All foreigners who are resident in Italy must apply for their tax identification number codice fiscale (an alphanumeric code of 16 characters which is similar to Social Security Number). This i.d is mainly used for tax purposes.
You are liable to be taxed after 180 days work (more than half the year) in Italy. Tax evasion in Italy is much more common than in the UK or US with over 80% of the population declaring an income of less than €4000pa. Many of us will be confused by the Italian system of tax amnesties and the reporting requirements for foreign investments. Not only is your income taxable but also your possessions. Seek advice from the commercialista.