A gratuity, or tip, is a voluntary payment made to service workers in addition to the cost of goods or services. Common service workers who receive tips include restaurant servers, taxi drivers, hair stylists, and bartenders. While not legally required, tipping certain service workers has become a social norm and convention in North America, usually ranging from 15-20% of the total bill for good service. Tips help supplement the income of many service workers who are paid at or below minimum wage.