In the United States, a tip is not legally required and the amount of the tip is at the discretion of the customer. However, it is important to understand cultural expectations of leaving a tip, as leaving an inadequate tip amount can be considered bad etiquette or even unethical.

The ethics of tipping are deeply subjective and depend entirely on the cultural and economic context of the location. In the United States, where the "tip credit" system allows employers to pay service staff a sub-minimum wage (as low as $2.13 per hour), many argue that not tipping is unethical because the customer is knowingly participating in a system where the server relies on gratuities for their basic livelihood. In this context, withholding a tip for anything other than egregious service is often seen as a failure to fulfill a social contract. Conversely, in many European and Asian countries, service workers are paid a full living wage, and "service" is already included in the bill or the menu price. In these cultures, tipping is truly an optional reward for exceptional effort, and not leaving one carries no ethical weight. Some critics of tipping culture argue that the system itself is unethical as it shifts the burden of fair wages from the employer to the consumer and can lead to discriminatory outcomes. Ultimately, while not "illegal," failing to tip in a tip-dependent economy is widely regarded as a breach of social ethics and a direct financial harm to the worker.