Tipping a waitress 15 percent is low, tipping 20 percent is good and tipping anything more is designated for exceptional service. In the United States, it is not mandatory to tip a waitress, server or bartender. Although it is not mandatory, service industry professionals generally make less than the minimum wage and rely on tips to make ends meet.
Many people feel they do not have to tip at all if they are not content with the level of service they receive in a restaurant. This practice is considered uncouth, and if a customer truly has a problem with the level of service, they should take it up with the management instead of taking it out on the waiter or waitress.