The Earned Income Tax Credit (EITC)
... is a special refundable credit for low to moderate income workers to reduce their federal income tax liability. Those who qualify will owe less and may be eligible for a larger refund. If you worked during 2009 and your adjusted gross income was less than $43,279 (or less than $48,279 for married workers) you may be eligible for a refund up to $5,657.
Workers making less than...
are not required to file a return, but should be encouraged to file since they may qualify for EITC or other tax credits.