When a government is considering whether to impose a tax or how to design a tax system, it has to weigh the benefits of a tax against its costs. We don’t usually think of a tax as something that provides benefits, but governments need money to provide things people want, such as national defense and health care for those unable to afford it. The benefit of a tax is the revenue it raises for the government to pay for these services. Unfortunately, this benefit comes at a cost—a cost that is normally greater than the amount consumers and producers pay. Let’s look first at what determines how much money a tax raises, then at the costs a tax imposes.