FullCalculator

Interest Penalty Calculator

Interest Penalty Calculator

Calculate interest accrued on overdue or underpaid amounts

$
%

Formula

Simple: Total = Principal × (1 + Rate × Days/365). Daily Compound: Total = Principal × (1 + Rate/365)^Days. Monthly Compound: Total = Principal × (1 + Rate/12)^Months.

Frequently Asked Questions

What is the IRS interest rate on underpayments?
The IRS charges interest on underpayments at the federal short-term rate plus 3 percentage points, compounded daily. This rate is updated quarterly. As of recent quarters, it has been around 7-8% annually.
How is penalty interest different from regular interest?
Penalty interest is charged as a consequence of late payment, underpayment, or default. It is typically higher than market interest rates and is meant to incentivize timely payment. Unlike regular interest, penalty interest may also include additional flat fees or surcharges.
Can penalty interest be waived?
In some cases, yes. The IRS may waive penalties (but not interest) for reasonable cause. For private debts, creditors may negotiate interest reductions. Late tax penalties can sometimes be waived under the first-time penalty abatement policy.

You may also need