WASHINGTON -- As Monday's federal income tax deadline approaches, nearly 2 million low-income families may be missing out on a tax break worth up to $953 because they don't file tax returns.

The tax break, known as the earned-income credit (EIC), is available to working parents with at least one child who earned less than $20,264 last year. But many of these families earn so little that they don't bother to file with the IRS, which is the only way to claim the credit, said Scott Barancik of the Center on Budget and Policy Priorities.

Although 12 million families claimed $6.7 billion in EIC benefits last year, Barancik said, many others didn't apply because they owed no taxes and didn't file a return.

"Recent research suggests that nearly 2 million eligible low-income families are failing to receive EIC payments they have earned," Barancik said.

He said those eligible for EIC can receive the tax break whether they owe taxes or not. If they do owe taxes, the amount of the EIC would be deducted from the amount owed. If no taxes are owed, the family would receive the EIC amount in full. A low-income family that has already filed a 1990 return without claiming the credit may refile by using Form 1040X.