It's entirely possible that your distribution was a subject to a 10% early-distribution penalty and the income falls in the 10% income tax bracket. If you only had 10% withheld for taxes, as is common for IRA distributions, you'll end up owing another 10% with your tax return. On Form 1040 or 1040A, the 10% income tax liability is added to the 10% early-distribution penalty and your 10% withholding is subtracted from that, leaving 10% due with your tax return.
