The rate at which an individual is taxed. Tax brackets are set based on income levels; individuals with lower income levels are taxed at a lower rate than individuals with higher income levels. Tax brackets serve as cutoff points for given income tax rates; therefore, if an individual's annual taxable income exceeds the cutoff point, that person is taxed according to the next tax bracket.

Most countries tax individual incomes using a system of tax brackets. This structure implements what is referred to as a progressive tax system, in which taxation progressively increases as an individual's income grows. This contrasts with a flat tax structure, in which all individuals are taxed at the same rate, regardless of their income levels.

Proponents of the use of tax brackets and a progressive tax system contend that individuals with high incomes are more able to pay income taxes while maintaining a high standard of living, while low-income individuals struggle to meet their basic needs, and should be subject to less taxation.

Furthermore, the use of tax brackets has an automatic stabilizing effect on an individuals' after-tax income, as a decrease in salary is counteracted by a decrease in tax rate, leaving the individual with a less substantial decrease in after-tax income.