The alternative minimum tax (AMT) was originally designed to ensure wealthy taxpayers paid at least a minimum amount of tax. However, due to the tax calculation, more and more taxpayers are becoming subject to the AMT. For instance, 3.6 million taxpayers paid the AMT with their 2005 tax returns, with that number projected to increase to 30 million, or 20% of all taxpayers, by 2010.
To calculate AMT, you add several common deduction items to your taxable income, subtract the AMT exemption amount ($62,550 for married taxpayers filing jointly, $42,500 for single taxpayers, and $31,275 for married taxpayers filing separately in 2006), and multiply the result by the AMT rates - 26% of the first $175,000 of income and 28% on amounts over that. If the AMT exceeds your regular income tax, the difference must be paid as the AMT.
Why are so many taxpayers becoming subject to the AMT? A primary reason is that ordinary income tax brackets are adjusted for inflation annually, while the AMT exemption amounts are not adjusted for inflation. Another reason is that regular income tax rates were recently reduced, while the AMT tax rates remained the same.
Low-income taxpayers are typically not subject to the AMT because the AMT exemption amounts shield them from the tax. Very wealthy taxpayers are also not typically affected because their overall tax rates are higher than the AMT tax rates. The Congressional Budget Office estimates that taxpayers earning between $50,000 and $200,000 will be the hardest hit by the AMT in the near future. It is estimated that if the AMT is not revised, it will affect 17% of taxpayers with income between $50,000 and $75,000, 53% of those with income between $75,000 and $100,000, 81% of those with income between $100,000 and $200,000, and 94% of those with income between $200,000 and $500,000 (Source: Urban-Brookings Tax Policy Center Microsimulation Model, 2005). By 2007, the U.S. government will receive more tax revenue from the AMT than from regular income taxes.