Seemingly without consistency, service charges of 10% to 15% may be added to hotel and restaurant bills. If you are unsure, be sure to ask if a tip is included; on the French side, it is customary. On top of the included service (service compris) it is usual to leave an extra 5%-10% in cash for the server. Taxi drivers, porters, chambermaids, and restaurant waitstaff depend on tips. The guideline is 10% to 15% for waitstaff and cabbies, $1 per bag for porters, and $5 per night per guest for chambermaids.