Calculate IRS failure-to-pay penalties and interest charges for late tax payments. See how quickly penalties and interest accumulate.
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Single filer in Los Angeles, $95,000 W-2 income, rents apartment, no dependents, contributes $7,000 to 401(k), standard deduction.
Takeaway: CA state tax alone adds ~$6,200 on this income — a 28% increase over the federal bill. Same income in Texas or Florida cuts total tax by roughly that amount. Use the calculator above with your W-2 box figures.
Most TCJA provisions expired after 2025 unless extended. The 2026 standard deduction, brackets, and rates may differ from 2024-2025 values depending on Congressional action. This calculator uses current published IRS projections — verify against your actual filing year.
This calculator handles federal liability. State rates vary from 0% (no income tax states) to 13.3% (California top marginal). City taxes exist in NYC, Philadelphia, Detroit, and others — they are not included here.
California State Tax CalculatorAlternative Minimum Tax applies when certain deductions (ISO stock options, large SALT deductions pre-TCJA) reduce regular tax below a threshold. AMT exemptions were enhanced under TCJA — but exposure still occurs for high-income earners exercising stock options.
If you have significant non-withholding income (self-employment, investments, rental), underpaying quarterly estimates triggers a penalty. The IRS safe harbor is paying 100% of prior year liability (110% if prior year AGI exceeded $150K). This calculator does not compute penalty amounts.
Long-term capital gains are taxed at 0%, 15%, or 20% — not at ordinary income rates. Adding capital gains to your income can also push ordinary income into a higher bracket even when the gains themselves are taxed at preferential rates.
Based on your inputs
4/day accrual
| Original Due Date | April 15, 2024 |
|---|---|
| Payment Date | 2024-10-15 |
| Days Late | 183 days (7 months) |
| Unpaid Tax Amount | $10,000 |
| Failure-to-Pay Penalty | $350 (3.50%) |
| Interest Charge | $401 (8.0% annual) |
| Total Penalty + Interest | $751 |
| Total Amount Due | $10,751 |
| Daily Accumulation | $4/day |
| Projected 90-Day Cost | $347 |
Key Points
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0.5% of unpaid taxes per month (or part of month), up to 25% total. Reduced to 0.25%/month if you have an installment agreement.
Interest accrues daily at the federal rate + 3% (typically 6–9%). It compounds annually and accrues from the original due date.
Filing an extension (Form 4868) extends the deadline to file, but NOT the deadline to pay. Penalties and interest still accrue from the original date.
If you pay by the original due date (April 15 for most), no failure-to-pay penalty or interest accrues, even if you file on extension later.
Failure to file is 5 percent of unpaid taxes per month up to 25 percent total, much higher than the 0.5 percent per month failure-to-pay penalty. Always file on time or request an extension even if you cannot pay.
Form 4868 extends the filing deadline by 6 months, from April 15 to October 15 for most taxpayers. This extension is automatic when filed on time, but it does not extend the payment deadline.
Yes. The IRS may waive penalties for reasonable cause such as natural disasters, serious illness, or death in the family. First-time penalty abatement is also available for taxpayers with a clean compliance history.
The combined failure-to-file and failure-to-pay penalty is 5 percent per month for the first 5 months, then 0.5 percent monthly after that. On a $5,000 tax bill, filing 3 months late costs approximately $750 in penalties alone.
If you miss the April 15 extension deadline, you are subject to both failure-to-file and failure-to-pay penalties from the original due date. File as soon as possible to stop the more expensive failure-to-file penalty.
The failure-to-file penalty maxes out at 25 percent of unpaid taxes. The failure-to-pay penalty also caps at 25 percent. Combined with interest, total penalties can reach 50 percent or more of the original tax owed.
Failure-to-Pay Penalty = Unpaid Tax × 0.5% × Months Late
(Max 25%; reduced to 0.25%/month on installment plan)
Interest = Unpaid Tax × (Federal Rate + 3%) × Days Late / 365
(2024 federal rate ~8%, varies quarterly)
Every formula on this page traces to a federal agency, central bank, or peer-reviewed institution. We cite the rule-makers, not secondhand blogs.
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Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.