Estimated Tax Underpayment Penalty Calculator

How it works

Under 26 U.S.C. 6654(d)(1) and IRS Topic No. 306, your safe-harbor floor is the smaller of two numbers. The first is 90% of this year's tax. The second is 100% of last year's 12-month tax. Under 26 U.S.C. 6654(d)(1)(C), that prior-year test rises to 110% if last year's AGI beat $150,000.00 ($75,000.00 if married filing separately). Under 26 U.S.C. 6654(e)(1), you also owe $0.00 when total tax minus withholding is under $1,000.00. In the default case, $20,000.00 of current tax and $15,000.00 of prior tax set four $3,750.00 installments.

26 U.S.C. 6654(c)(2) sets the four due dates on April 15, June 15, September 15, and January 15 of the next year. Under 26 U.S.C. 6654(b)(3), each payment goes to the oldest unpaid Form 2210 installment first. You cannot tag a late check to a newer quarter while an older one is still short. Under 26 U.S.C. 6654(b)(2), daily interest runs from the due date until the day you pay or April 15, whichever comes first.

Under 26 U.S.C. 6654(g)(1) and the Instructions for Form 2210 (2025), federal tax withheld is split into four equal parts on the four due dates. You can use actual withholding dates instead by checking box D in Part II of Form 2210. When a due date falls on a weekend or legal holiday, the Form 2210 instructions count a payment on the next business day as on time. For 2025, Sunday, June 15 shifted to Monday, June 16, 2025.

Under 26 U.S.C. 6621(a)(2), the individual rate is the federal short-term rate plus 3 percentage points. Under 26 U.S.C. 6621(b)(3), that short-term rate is rounded to the nearest full percent. The IRS Quarterly interest rates page lists 7% for all four quarters of 2025. For 2026, it lists 7%, 6%, 7%, and 7% for the four quarters, and IR-2026-98 confirms 7% for the fourth quarter. Under 26 U.S.C. 6621(b)(2)(B), the March rate also covers the first 15 days of April. That is why the Form 2210 (2025) worksheet keeps the 7% rate from Q1 2026 all the way through April 15, 2026.

Formula

Form 2210 required annual payment = min(90% of this year's tax, 100% or 110% of last year's tax)
Form 2210 required installment = 25% of the required annual payment, due April 15, June 15, September 15 and January 15
unpaid on installment k, any day = min(installment, max(0, k × installment − payments made through the day before))
penalty = Σ over installments and days (after the due date, to April 15) of unpaid × daily rate
daily rate = the IRS underpayment rate for the day's quarter ÷ 365

Example

Adapted from Example 2 of the Form 2210 instructions, with this page's own amounts ($4,800.00 prior-year tax, $1,200.00 per quarter). Paying $700.00 on April 15 leaves $500.00 unpaid. A $1,700.00 payment on June 10 clears that $500.00 April gap first, so it runs 56 days at 7%: $500.00 × (56 ÷ 365) × 7% = $5.37. The other $1,200.00 covers June on time for a $0.00 second-quarter charge.

Default case ($20,000.00 current tax, $15,000.00 prior tax, $70,000.00 prior AGI). The 90% current-year test is $18,000.00, so the smaller $15,000.00 prior-year floor wins ($3,750.00 per quarter). You pay $3,750.00 on April 15, nothing in June, $7,500.00 on September 15, and $3,750.00 on January 15. The June installment is late for 92 days: $3,750.00 × (92 ÷ 365) × 7% = $66.16.

Single year-end payment ($15,000.00 paid in one lump sum on January 15, 2026). Each quarterly target is $3,750.00. The April quarter is 275 days late, June is 214 days late, and September is 122 days late. The January quarter is on time. At 7%, the total charge is $3,750.00 × 7% × (275 + 214 + 122) ÷ 365 = $439.42.

Full-year Table 2 benchmark ($4,000.00 prior-year tax, $1,000.00 per quarter, $0.00 paid before April 15, 2026). The first quarter stays unpaid across all four rate periods (76 + 92 + 92 + 105 = 365 days) and costs $70.00 at 7%. Across all four quarters using the Table 2 day counts, the total penalty is $186.22.

Assumptions and limitations

• Follows 26 U.S.C. 6654, Form 2210 (2025), and the Instructions for Form 2210 (2025). Published quarterly rates come from the IRS Quarterly interest rates page and IR-2026-98 through December 31, 2026. For tax year 2026, days in early 2027 use the rate you enter.
• Models the Form 2210 regular method only. The January 31 return cutoff and Form 2210-F farm and fishing rules are not modeled. Form 2210 Part II elections — boxes A and B waivers, box C Schedule AI, box D actual withholding dates, and box E joint-to-separate splits — are outside this page, as are state penalties.
• Uses last year's tax only when you select a 12-month prior return. Under the Form 2210 instructions, a 12-month prior return with $0.00 tax sets the prior-year floor to $0.00. Payments count on the date entered (use the postmark date for mailed checks) for up to 60 lines in the tax year and the next year.
• Scenario tables and comparison rows vary one input at a time while holding your other entries fixed. Lowering last year's tax shrinks each Form 2210 quarterly target while the prior-year floor is the smaller test, and your listed payment dates and amounts stay unchanged.

These figures are estimates for learning and planning, not financial, tax, legal or investment advice. Terms of use.

What to do with the result

Check the Form 2210 flowchart before filing the form. The Form 2210 (2025) instructions state that unless box A, B, C, D, or E in Part II applies, you should not attach Form 2210. The IRS will figure any penalty, such as the $66.16 in the default case, and mail a bill. No interest runs on that bill if you file by April 15 and pay by the notice date.

Test the annualized income method if your pay arrived late in the year. If you earned most of a $20,000.00 tax bill in the fall, open the annualized income installment calculator. Filing Form 2210 Schedule AI (Part II box C) can shrink your April and June targets.

Use late-year W-2 or pension withholding to fix earlier quarters. Withholding spreads 25% onto each due date. Adding $4,000.00 of W-2 withholding in the federal paycheck withholding calculator credits $1,000.00 to each quarter and cuts the default penalty to $30.88. Raising withholding to $8,000.00 cuts it to $0.00.

Set next year's safe-harbor schedule or check refund deadlines. Use the quarterly estimated tax calculator to lock in 4 equal payments of $3,750.00, the 25% installments of 26 U.S.C. 6654(d)(1)(A). If you overpaid old vouchers, check the tax refund claim deadline calculator.

Frequently asked questions