Income tax return for taxation also vary, making comparisons all the more difficult. Countries that tax income generally use one of two systems: territorial or residential. In the territorial system, only local income – income from a source inside the country – is taxed. In the residential system, residents of the country are taxed on their worldwide (local and foreign) income, while nonresidents are taxed only on their local income. In addition, a very small number of countries, notably the United States, also tax their nonresident citizens on worldwide income. Countries with a residential system of taxation usually allow deductions or credits
Negative income tax for the taxes drawn at the source is flat) which is positive once the income exceeds the tax exemption. If, however, the income is less than the tax exemption, the effective progressive rate actually becomes negative without any involvement by any tax authority. As for the positive progression, only very high incomes would lead to an actual tax rate which is close to the nominal flat tax rate. The tax on tax exemption also can be understood as a tax credit, which is paid back once an income has reached the level of the tax exemption. This level marks the