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Bed and breakfast is an expression of English origin (translatable as bed and breakfast) to denote a form of tourist accommodation informal, commonly abbreviated as B & B. It is practiced by households with one or more guest rooms free, with or without private bathroom, and includes accommodation and breakfast.
It is generally cheaper in other forms of tourist accommodation as a hotel or residence, and more expensive than in hostels or campsites. Often, the B & B is an opportunity for companionship and knowledge for families or single people are happy to accommodate and welcome travelers.
Italian law:
The B&B in Italy are regulated by regional laws, and are present in all regions. One of the common features is that this is a family run business, that is conducted by individuals within the home and abode, the place that is. where you live normally. The maximum number of rooms and beds used for the service varies according to regional law, but usually there is a limit of three double bedrooms. The breakfast provided shall be composed of pre-packed food (B & B are not allowed to prepare, handle and serve food, unless otherwise provided by regional authorities).
A second street, location, presence or not of the bath room, services offered (changing sheets, cleaning, tv or other electronic devices in room, breakfast type, etc..), The B & B are in some provinces Companies classified by the Provincial Tourist Office (APT) or by specific municipal committees. There are still a few areas where there is a classification, is often not appreciated by the operators themselves who are thus frustrate the peculiarities of each B & B for a standardization of service provided. Some groups classify the B & B but these classifications do not have any validity to international or domestic, are simple criteria to ensure the existence of certain equipment or services within a structure.
Normally, to open a B&B is just the beginning of the report and the prices at the tourist office of the municipality or the APT. From a tax point of view, (according to the resolution of the Ministry of Finance No. 155, 13/10/2000), there is no need to open the VAT because the activity of B & B should be exercised from time to time, and it is sufficient tax identification number of the owner to be used on the receipt (no tax) which is required to issue at the time of payment. For amounts greater than the 77.47 euros is also required to put on a receipt stamp from EUR 1.81, which generally is made payable to the customer (the requirement of affixing, however, is borne by the operator).
Since by law saltuaria activity is also required to close for at least 3 months per year (according to the new laws should be passed within a short 2 months, cf. Lazio new regulation), and are not permitted to stay more than 30 days consecutive.

source Wikipedia