At the time of writing, holders of USA, Canadian, Australian and New Zealand passports do not need to apply for a visa before entering Italy if they are travelling as tourists only. On entry, visitors are automatically granted a 3 month permit to stay, which encompasses the right to come and go from Italy as required. Travellers from the UK, Denmark and Ireland are allowed entry under the Schengen treaty on presentation of a valid passport whilst members of other EU countries must present a valid passport or national identity card. However, global and politics is a dynamic affair and all travellers are advised to check with their airlines or the Italian consulate well before leaving.
As a requirement of Italian Law, we must take the identification details from the passports or identification cards of all guests in our villas and apartments for local police records.
It is law in Italy that all people must have valid identification on them at all times and would suggest that at least a photocopy of a valid passport be inserted into your wallet.