Updated : 10/2013
Some EU countries require you to report your presence to the relevant authorities (often the town hall or local police station) within a reasonable period of time after arrival and may impose a penalty, such as a fine, if you fail to do so.
Before you go to another country, please check the deadlines and relevant conditions for reporting your presence there with the national authorities.
All you need to report your presence as EU national is your identity card or passport; if you are accompanied by family members who are not EU nationals, they will need a passport. You should not have to pay any fees. If you are staying in a hotel, it is usually enough to fill in a special form - the hotel will take care of the rest.
In some EU countries, failure to report your presence might result in a fine, but you cannot be expelled just for this.
Hans is Austrian and spends his summer holiday every year on the Italian coast. Last summer he stayed in Italy for 2 months in his own flat. He reported his presence but the Italian authorities asked him to register at the town hall as well and to prove he had sufficient means to support himself in Italy.
But Hans is entitled to stay in Italy for up to 3 months without providing any documents other than his identity card. If he stays for such a short period only, the Italian authorities can ask him to report his presence, but not to register.