Millions of taxpayers have to file a tax return by mid-April to avoid big penalties. But some lucky taxpayers don't have to file a tax return at all. How do you know if you're eligible for this lucky break -- and whether you should file even if you do qualify?

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, looks at the filing requirements for income tax returns. Dan notes that below certain income limits -- $10,000 for single filers, $20,000 for joint filers, $12,850 for heads of household, and $16,100 for qualifying widow and widowers, you're not required to file a return. But Dan also points out that sometimes, you should file a return anyway even if you're not required to. For instance, if you're due money back from prior payroll tax withholding or from a refundable credit like the earned income credit, adoption credit, American Opportunity Credit, and other eligible provisions, then it makes sense to file to get a refund even if you technically don't have to. For most taxpayers, though, filing will still be part of annual life.

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