The Alternative Minimum Tax bomb exploded January 1, 2010, because Congress failed to pass legislation that would have prevented the tax from affecting millions of taxpayers.  The number of taxpayers affected by the AMT will jump from 4 million in calendar year 2009 to 27 million in 2010.  As the reach of the AMT grows under current law, many taxpayers will face a fundamentally altered tax structure.  If nothing is changed this year, one in six taxpayers will be affected by the AMT, paying on average an additional $3,900 in tax, and nearly every married taxpayer with income between $100,000 and $500,000 will owe some alternative tax.  Because of the particular tax preferences and exemptions disallowed under the AMT, that tax structure is more likely to affect married couples, large families, and taxpayers in states with high state and local taxes.  See the Congressional Budget Office’s January 15, 2010, report called “The Individual Alternative Minimum Tax.”