A tax system is a set of rules that a government uses to collect taxes. The system can be progressive, meaning that the tax rate goes up as the amount of money earned goes up. The system can also be regressive, meaning that the tax rate goes down as the amount of money earned goes down. The system can also be proportional, meaning that the tax rate is the same for everyone. The purpose of a tax system is to raise revenue for the government in order to finance public expenditure. A well-designed tax system should be efficient, equitable, and simple.