As AndreaC1 just pointed out, certain credits (the refundable ones) can give you a refund over and above any tax payments made. Yes, the Earned Income Credit can give you a refund even if you don't owe any (or very little) federal income tax, and didn't pay any withholding or estimated taxes during the year. This is contrary to the way that a lot of people think about refunds (that the refund is some of the money you paid in during the year being returned to you because it was more than the tax due).
On your return, are there any of the credits listed above? The credits would generally be on Schedules 3 and 5 of form 1040.
