Estimated Tax Penalty Calculator
Check if you'll owe an IRS underpayment penalty and how to avoid it with the safe harbor rules.
Tax & Payment Information
Your total federal tax owed for 2026
Total W-2 withholding for the year
Quarterly Estimated Payments
Penalty Analysis
| Safe Harbor Test | Required | Status |
|---|---|---|
| 90% of current year tax | $22,500 | FAIL |
| 100% of prior year tax | $22,000 | FAIL |
| Owe less than $1,000 | Under $1,000 owed | FAIL |
| Quarter | Due Date | Required | Paid | Shortfall |
|---|---|---|---|---|
| Q1 | Apr 15 | $5,500 | $5,250 | $250 |
| Q2 | Jun 15 | $5,500 | $5,250 | $500 |
| Q3 | Sep 15 | $5,500 | $5,250 | $750 |
| Q4 | Jan 15 (next year) | $5,500 | $5,250 | $1,000 |
How to Avoid the Penalty
- 1.No safe harbor met — you may owe a penalty of ~$108
- 2.2026 quarterly due dates: April 15, June 15, September 15, January 15 (2027)
- 3.Withholding counts as paid evenly throughout the year — increase W-4 withholding to avoid penalties
- 4.File Form 2210 to calculate your exact penalty — or let the IRS calculate it for you (they'll send a bill)
This is a simplified penalty estimate. The IRS uses daily compounding and may calculate a different amount. File Form 2210 for the exact calculation.
How the IRS Underpayment Penalty Works
If you don't pay enough tax throughout the year — through withholding or estimated payments — the IRS charges a penalty on the underpaid amount. The 2026 penalty rate is approximately 8% per year (updated quarterly based on federal short-term rate + 3%). The penalty compounds daily, calculated separately for each quarter's shortfall from the due date until the tax is paid.
Three Ways to Avoid the Penalty (Safe Harbor)
| Safe Harbor Rule | What It Means | Best For |
|---|---|---|
| 90% of current year tax | Pay at least 90% of what you owe | Predictable income |
| 100% of prior year tax (110% if AGI over $150K) | Pay at least your prior year's total tax | Variable income, growing income |
| Owe less than $1,000 | Balance due under $1,000 | Most W-2 employees |
2026 Quarterly Estimated Tax Deadlines
| Quarter | Income Period | Due Date |
|---|---|---|
| Q1 | January 1 – March 31 | April 15, 2026 |
| Q2 | April 1 – May 31 | June 15, 2026 |
| Q3 | June 1 – August 31 | September 15, 2026 |
| Q4 | September 1 – December 31 | January 15, 2027 |
Frequently Asked Questions
Can I avoid the penalty by paying extra in Q4?
Partially. The IRS calculates penalties per quarter, so if you underpaid in Q1–Q3 but make a large Q4 payment, you'll still owe penalties for the earlier quarters. However, a smarter strategy is to increase your W-4 withholding late in the year — withholding is treated as paid evenly throughout the year, effectively covering earlier shortfalls retroactively.
What if my income varies throughout the year?
Use the annualized income installment method (Form 2210, Schedule AI) to calculate penalty based on when you actually earned income. If most of your income came in Q4, this method can significantly reduce or eliminate your penalty. This is particularly useful for freelancers with seasonal income or anyone who received a large bonus late in the year.
See also: Quarterly Tax Calculator and Tax Refund Estimator.