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
Working Tax Credit Prime Minister Tony Blair also apologised to Parliament over the incident. The Working Tax Credit scheme was subject to much criticism, particularly in the wake of the difficulties surrounding its implementation. Criticism focused on the way that credits are calculated on an annual basis, leading to overpayment, followed by large demands for repayment, which those on low income may find difficult to meet. David Harker, chief executive of Citizens Advice, commented "This is an untenable system. An annualised system doesn't provide the stability of income required by low income families." In addition, the scheme was accused of being over-complicated and