What happens if I can’t pay my quarterly tax underpayment by April 15?

File your return by April 15 (or get an extension). Apply for an IRS installment agreement online at irs.gov/paymentplan. The agreement stops enforcement actions (liens, levies) and spreads payment over up to 72 months at 8% annual interest. Always file on time even if you can’t pay — the failure-to-file penalty (5%/month) is much worse than the failure-to-pay penalty (0.5%/month).

What is the IRS failure-to-pay penalty?

0.5% of unpaid tax per month (up to 25% total). On a $10,000 balance: $50/month. This is separate from and in addition to interest (8% annualized in 2025). The failure-to-file penalty is much worse: 5%/month (up to 25%). Always file on time, even if you can’t pay in full.

How do I calculate my underpayment penalty?

Use Form 2210 (Underpayment of Estimated Tax) or use tax software which calculates it automatically. The penalty is 8% annualized on the shortfall per quarter for the days it was underpaid. For a complete year of $5,000 underpayment: approximately $400 in penalty.

Can the underpayment penalty be waived?

The estimated tax underpayment penalty (Form 2210 penalty) is generally not waivable except for documented unusual circumstances (natural disaster, serious illness, etc.). The failure-to-pay penalty (separate from underpayment) may be waived under First-Time Abate if you have a clean compliance history. Call the IRS to request FTA after paying your balance.

How do I prevent underpayment next year?

Use the safe harbor: pay 100% of this year’s total tax in quarterly installments next year (110% if AGI exceeds $150,000). Then work with a CPA or use a quarterly tax calculator to optimize within safe harbor. The safe harbor ensures no penalty; optimization minimizes the balance due or creates a refund.

Recovering From Quarterly Tax Underpayment: Your Action Plan

Discovering in February that you significantly underpaid quarterly taxes is stressful — but the resolution is straightforward, and the path forward is clearer than it seems in the moment. Here is exactly what to do when you’ve underpaid estimated taxes.

Immediate Actions When You Discover Underpayment

Step 1: Calculate your actual annual tax liability accurately (using a calculator or CPA). Step 2: Calculate total quarterly payments made. Step 3: Determine the shortfall: Actual tax − Quarterly payments made = Balance due + potential penalty. Step 4: File your return on time regardless of payment ability (filing extension only — not payment extension). Step 5: Pay as much as possible by April 15; remainder can be paid via installment agreement.

Recovery actions by underpayment scenario

Situation	Action	Cost
Balance under $1,000 due at filing	Pay in full by April 15	No penalty
Balance $1,000–$5,000 due	Pay in full or apply for 60-day payment extension	8% interest on balance after April 15
Balance over $5,000	File by April 15; set up IRS installment agreement	8% interest + possible failure-to-pay penalty
Can’t file by April 15	File extension (Form 4868) by April 15; pay estimated balance	Avoids failure-to-file penalty (5%/month)
Prior year safe harbor met despite balance due	No underpayment penalty; just owe the balance	Only interest on unpaid balance after April 15

Setting Up an IRS Installment Agreement

If you cannot pay your full tax balance by April 15: apply for an installment agreement at irs.gov/paymentplan. Online agreements: for balances under $50,000, available immediately. Terms: up to 72 months at 8% annual interest (approximately 0.67% per month on remaining balance). Monthly payment = balance ÷ chosen months. The agreement prevents liens and enforcement while you pay.

💡First-Time Penalty Abatement

If you have a clean compliance history (no penalties in the prior 3 years), call the IRS at 1-800-829-1040 after filing and paying your balance, and request 'First-Time Abate' (FTA) for failure-to-pay or failure-to-file penalties. This waiver is granted routinely to eligible taxpayers and can eliminate hundreds in penalties.

Calculate Your Correct Quarterly Payments Going Forward

Enter your projected current-year income to set up accurate quarterly payments and prevent a repeat of underpayment.

Open Quarterly Tax Calculator →

Recovering From Quarterly Tax Underpayment: Your Action Plan

Immediate Actions When You Discover Underpayment

Setting Up an IRS Installment Agreement

Frequently Asked Questions

Frequently Asked Questions

More Quarterly Tax Guides

How to Use a Quarterly Tax Calculator: Step-by-Step Guide

Quarterly Tax Payment Benchmarks: What Should You Pay?

Quarterly Estimated Taxes on $50,000 Self-Employment Income