Roughly half of Americans who pay no Federal income tax do so because they simply don't earn enough money. The other half doesn't pay taxes because of special provisions in the tax code that benefit certain taxpayers, notably the elderly and working families with children. For example, the tax code excludes a portion of Social Security income and gives larger standard deductions and tax credits to the elderly. And many working families with children qualify for both the child credit and the earned income tax credit. Together, the elderly and working families with children account for 74 percent of all nontaxable households that aren't excluded by income level alone [source: Williams].