Thanks @pk. The penalty for unpaid state tax, so I've read, is 5% of the total + 0.5% for each month late. Would this be counted as an unpaid state tax (underpayment), however?
EDIT: Looking this up and the IRS calls it an "excessive payment" for which they do impose a penalty. Can't find anything about the state, though. Fortunately my federal return was correct.
