Underpayment Of Estimated Tax Penalty Rate 2025. Yes, if the q1 through q3 estimated tax payments were equal amounts and 3/4 of the the tax withholding would be sufficient to make up for the underpayment for q1 through. We pay you interest on certain tax liabilities when you pay early, overpay or there's a delay in us paying your refund.

The instalment rate calculation is: (estimated (notional) tax ÷ instalment income) × 100.