Underpayment Penalty Love Machine 14 years ago Underpayment PenaltyTax penalties imposed when an individual fails to pay his or her estimated tax in full.Random Finance Terms for the Letter UUnderfunded Pension PlanUnderinvestment ProblemUnderlyingUnderlying AssetUnderlying CostUnderlying ProfitUnderlying SecurityUnderpayment PenaltyUnderperformUnderpricingRecommended for you:UnderperformUnderinvestment ProblemUnderlying ProfitUnderfunded Pension Plan