Negative income tax notion has long been popular in some circles, its implementation has never been politically feasible. This is partly because of the very complex and entrenched nature of most countries' current tax laws: they would have to be rewritten under any NIT system. However, some countries have seen the introduction of refundable (or non-wastable) tax credits which can be paid even when there is no tax liability to be offset, such as the Earned Income Tax Credit in the United States and working tax credit in the UK. In 1971, President Richard Nixon proposed a negative income tax as the centerpiece
Income tax partnership firms are also taxed at flat rate. Most jurisdictions exempt locally organized charitable organizations from tax. Capital gains may be taxed at different rates than other income. Credits of various sorts may be allowed that reduce tax. Some jurisdictions impose the higher of an income tax or a tax on an alternative base or measure of income. Taxable income of taxpayers resident in the jurisdiction is generally total income less income producing expenses and other deductions. Generally, only net gain from sale of property, including goods held for sale, is included in income. Income of a corporation's shareholders usually