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
Income tax in the Netherlands however, specify how the benefit of the 30% rule should be divided between the employee and the employer. Some employers (e.g. Shell) have stipulated in their general working conditions that the 30% rule income tax benefit is solely for the benefit of the company, arguing that salaries of their local workers would not be on par with their foreign work force. The 30% rule income tax benefit is then divided between an employee and the employer up to the level as if the foreigner employer fictively paid the income tax on the entire salary and the surplus left to the