You might not have heard of the Earned Income Tax Credit, but it may help you get a tax refund of thousands of dollars from the Internal Revenue Service. 

This tax credit generally applies to lower- and moderate-income workers. When you complete the form while doing your taxes, it can help you to recoup some or all of the money you've already paid to the IRS. It might even give you a tax refund that is more than you've paid in taxes.

How much you receive depends on your income, marital status, and how many children (dependents) you have. A single person without children making almost $15,000 a year could get back more than $500. A married couple with three children making almost $50,000 could get more than $6,000. The average earned income tax credit for 2015 was $2,455, according to the IRS.

While millions of working Americans qualify, 1 in 5 households eligible for the earned income tax credit claims it, according to the IRS. Those who don't file federal tax returns because they made less in 2016 than the filing minimum, for instance, might be eligible for this tax refund. (For single people under age 65, that's $10,350; for couples filing jointly under age 65, it's $20,700.) It could be worth filing anyway, just to get the tax refund.

To find out whether you can benefit from the earned income tax credit, you can visit a tax preparer, use tax preparation software, or turn to the EITC Assistant, which is provided by the IRS. Lower and middle-income families and seniors can use free tax-prep services through various government and volunteer programs. The AARP Foundation Tax-Aide service, for instance, will pair you with trained volunteers. You can also prepare and file yourself for free using IRS FreeFile or the free versions of commercial tax software.