The earned income tax credit, or EITC, is available to workers who don't make much money. It was created to help offset the cost of Social Security payments. The credit is available to single taxpayers, but pays more to taxpayers who are supporting families. The credit also is refundable, which means that if a taxpayer doesn't owe any income tax, the filer could get a refund from the IRS.
In recent years, the EITC has become a political lightning rod. Advocates say it encourages people to work. Opponents say the refundable aspect is particularly unfair to other workers who don't qualify.
But there's no argument over the tax credit's cost: an estimated $294 billion between 2011 and 2015.