The United States federal Earned Income Tax Credit (EITC or EIC) is a refundable tax credit designed to encourage low-income workers and offset the burden of U.S. payroll taxes. For tax year 2009, a claimant with one qualifying child can receive a maximum credit of $3,043. A claimant with two qualifying children can receive a maximum credit of $5,028. The credit is expanded for tax year 2009 and 2010. For claimants with three or more qualifying children, the maximum credit is $5,657. Grandparents, aunts, uncles, and siblings can also claim a child as their qualifying child provided they shared residence with the child for more than six months of the tax year. However, in tie-breaker situations in which more than one filer claims the same child, priority will be given to the parent. A foster child also counts provided the child has been officially placed by an agency or court. There is a much more modest EIC for persons and couples without children that reaches a maximum of $438.^[1]

http://en.wikipedia.org/wiki/Earned_income_tax_credit

Earned income is a technical term defined by the United States tax code. The following are the main sources:^[2]

• Wages, salaries, tips, commissions, and other taxable employee pay,
• Net earnings from self-employment,
• Gross income received as a statutory employee,
• a minority of disability payments, and
• nontaxable combat pay which a member of the U.S. armed services elects to include solely for purposes of EIC calculation. The service member must include either all of the combat pay in this calculation or none of it.

http://en.wikipedia.org/wiki/Earned_income_tax_credit