An income tax is a tax levied on the financial income of persons, corporations, or other legal entities. Various income tax systems exist, with varying degrees of tax incidence. Income taxation can be progressive, proportional, or regressive. When the tax is levied on the income of companies, it is often called a corporate tax, corporate income tax, or corporation tax. Individual income taxes often tax the total income of the individual (with some deductions permitted), while corporate income taxes often tax net income (the difference between gross receipts, expenses, and additional write-offs).