Flat tax

A flat tax (short for flat tax rate) is a tax system with a constant marginal rate, usually applied to individual or corporate income. A true flat tax would be a proportional tax, but implementations are often progressive and sometimes regressive depending on deductions and exemptions in the tax base. There are various tax systems that are labeled "flat tax" even though they are significantly different.

Flat tax proposals differ in how the subject of the tax is defined.

A true flat rate tax is a system of taxation where one tax rate is applied to all personal income with no deductions.

Where deductions are allowed, a 'flat tax' is a progressive tax with the special characteristic that, above the maximum deduction, the marginal rate on all further income is constant. Such a tax is said to be marginally flat above that point. The difference between a true flat tax and a marginally flat tax can be reconciled by recognizing that the latter simply excludes certain types of income from being defined as taxable income; hence, both kinds of tax are flat on taxable income.

Modified flat taxes have been proposed which would allow deductions for a very few items, while still eliminating the vast majority of existing deductions. Charitable deductions and home mortgage interest are the most discussed examples of deductions that would be retained, as these deductions are popular with voters and are often used. Another common theme is a single, large, fixed deduction. This large fixed deduction would compensate for the elimination of various existing deductions and would simplify taxes, having the side-effect that many (mostly low income) households will not have to file tax returns.

Designed by economists at the Hoover Institution, Hall–Rabushka is a flat tax on consumption. Principally, Hall–Rabushka accomplishes a consumption tax effect by taxing income and then excluding investment. Robert Hall and Alvin Rabushka have consulted extensively in designing the flat tax systems in Eastern Europe.

The negative income tax (NIT), which Milton Friedman proposed in his 1962 book Capitalism and Freedom, is a type of flat tax. The basic idea is the same as a flat tax with personal deductions, except that when deductions exceed income, the taxable income is allowed to become negative rather than being set to zero. The flat tax rate is then applied to the resulting "negative income," resulting in a "negative income tax" that the government would owe to the household—unlike the usual "positive" income tax, which the household owes the government.

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