Under current law, taxpayers who itemize deductions may deduct the amount they donate to charities from their adjusted gross income (AGI) when determining how much they owe in federal income taxes. That deduction gives people who itemize an incentive to contribute to charities. Like other forms of preferential tax treatment, the deduction also costs the federal government revenues that it might otherwise collect. At current levels of charitable giving, the cost of that deduction— measured as the additional revenues that could be collected if the deduction was eliminated—will total about $230 billion between 2010 and 2014, according to the Joint Committee on Taxation (JCT). Numerous proposals have been made in recent years to alter the incom...