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Calculator · IRC §6654 · Tax year 2026

2026 US Quarterly Estimated Tax Calculator

Two numbers from last year — prior-year AGI and total tax — are enough to compute the IRC §6654 safe-harbor minimum for 2026 and the per-quarter payment that keeps you out of the underpayment-penalty zone. Optionally add a current-year projection to unlock the 90%-current-year path.

The safe harbor in five lines

  • Safe harbor = pay quarterly estimates that meet the lower of two paths: 90% of current-year tax OR 100% of prior-year tax (110% if prior-year AGI was over $150k).
  • Four 2026 deadlines: Apr 15, Jun 15, Sep 15, Jan 15, 2027. None shift for weekends in 2026.
  • For most growing freelancers the prior-year path wins — last year's tax is the known smaller number.
  • Pay via IRS Direct Pay, EFTPS, or Form 1040-ES voucher. Direct Pay is free and verifies in seconds.
  • Underpayment penalty is daily interest at the IRS short-term rate + 3 percentage points (~7-8% APR in 2026), not a flat fine.
Apr 15, 2026
Q1 2026
Jun 15, 2026
Q2 2026
Sep 15, 2026
Q3 2026
Jan 15, 2027
Q4 2026

All four 2026 deadlines land on a weekday — no weekend/holiday shift applies. Q4 is due after year-end because §6654(c) pairs each quarterly payment with the period it covers, not the calendar quarter itself.

Live calculator

Your numbers

Two numbers from last year + an optional current-year projection. We compute the IRC §6654 safe-harbor minimum and the per-quarter payment that keeps you penalty-free.

Adjusted gross income from your most recent filed return. Triggers the 110% multiplier above $150,000.

Last year's total federal tax liability — not what you owed or were refunded.

Leave blank to use prior-year safe harbor only. Adding a projection unlocks the 90%-current-year path, which can be lower when this year's income is well below last year's.

Enter your figures above to see your estimate.

How the §6654 safe harbor actually works

IRC §6654(d)(1) gives taxpayers a minimum-payment rule that avoids the underpayment penalty. You are safe if your total withholding + estimated payments for the year meet either:

  1. 90% of the current-year tax shown on your 2026 return, OR
  2. 100% of the prior-year tax shown on your 2025 return — 110% if your 2025 AGI exceeded $150,000 (married-separate: $75,000) per §6654(d)(1)(C) if you were a higher earner.

You pay the lower of the two. For most solo freelancers with growing income, path #2 wins because last year's tax is the known, smaller number. The calculator defaults to this path and only introduces the 90%-current-year path when you provide a projection.

Four scenarios, walked through with numbers

Steady freelancer

Prior-year AGI $90,000, prior-year tax $14,000

  1. Below the $150,000 AGI threshold → 100% prior-year path applies.
  2. Annual safe-harbor minimum: $14,000.
  3. Per-quarter payment: $14,000 / 4 = $3,500.
  4. Pay $3,500 by Apr 15, Jun 15, Sep 15, Jan 15, 2027 → no §6654 underpayment penalty regardless of what 2026 actually owes.

Crossed $150k AGI last year

Prior-year AGI $180,000, prior-year tax $38,000

  1. Prior-year AGI exceeds $150,000 → 110% multiplier kicks in per §6654(d)(1)(C).
  2. Annual safe-harbor minimum: $38,000 × 1.10 = $41,800.
  3. Per-quarter payment: $41,800 / 4 = $10,450.
  4. The 10% premium relative to last year's tax is the cost of the 110% rule. It is fixed — you can dodge it only by switching to the 90%-current-year path with a projection.

Income dropped this year

Prior-year tax $20,000, projected 2026 tax $9,000

  1. Path A (prior-year, 100%): $20,000.
  2. Path B (current-year, 90%): $9,000 × 0.90 = $8,100.
  3. Pay the lower → safe-harbor minimum: $8,100.
  4. Per-quarter payment: $8,100 / 4 = $2,025.
  5. The current-year path requires confidence in your projection — under-projecting and missing the 90% target retroactively triggers penalties on the shortfall. If unsure, project conservatively (assume more income).

W-2 + side hustle

W-2 withholding $11,000, prior-year total tax $15,000

  1. Annual safe-harbor minimum: $15,000 (100% prior-year).
  2. W-2 withholding of $11,000 counts toward the safe harbor and is treated as paid evenly across the four quarters per §6654(g) — so it credits $2,750/quarter automatically.
  3. Required quarterly estimate: ($15,000 − $11,000) / 4 = $1,000/qtr.
  4. If side-hustle income spikes mid-year, raising W-2 withholding via a new W-4 is the cleanest cure — withholding is retroactively even, estimated payments are not.

Drop these prior-year-tax numbers into the calculator above to confirm. Shareable URL encodes the scenario for handing to a CPA.

What the penalty actually costs if you miss it

The §6654 penalty is not a flat fee — it is a daily interest charge on the shortfall, computed at the IRS short-term federal rate + 3 percentage points. The rate resets each calendar quarter. For 2026 the combined rate is in the 7–8% APR range, applied for every day between the missed due date and the final April-15 filing date (or the date you make the payment, whichever is earlier).

A $5,000 Q1 underpayment that you only true-up at filing on Apr 15, 2027 carries roughly $380 of penalty interest at today's rates — small enough that paranoid planning is not required, large enough that consistent missing is expensive. The safe-harbor math keeps you structurally out of the penalty calculation.

Frequently asked questions

Who has to pay quarterly estimated taxes?

Anyone whose total tax bill (federal income + SE) is expected to be at least $1,000 after withholding. IRC §6654(e)(1) sets the floor. In practice that means most 1099 freelancers, gig workers, single-member LLCs, and S-Corp owner-employees with distributions on top of W-2 wages.

What is the §6654 safe harbor exactly?

A two-path minimum-payment rule that takes you out of underpayment-penalty exposure. You are safe if your total withholding + timely estimated payments meet either: (a) 90% of current-year tax, or (b) 100% of prior-year tax (110% if your prior-year AGI exceeded $150,000). You pay the lower of the two.

When is the 110% rule triggered instead of 100%?

When your prior-year AGI exceeded $150,000 ($75,000 married filing separately). Above that threshold, the prior-year safe-harbor multiplier flips from 100% to 110% per IRC §6654(d)(1)(C). The calculator above checks this automatically when you enter prior-year AGI.

Are the four payments equal, or can I weight them?

Default is four equal payments — the calculator computes safe-harbor / 4 per quarter. If your income is lumpy (e.g. most of your revenue lands in Q3), you can use the annualized income installment method on Form 2210 Schedule AI to weight payments to actual income periods. More paperwork, but it can defer cash. Most solo freelancers stick with equal quarters.

What are the 2026 quarterly deadlines exactly?

Q1: April 15, 2026 (covers Jan-Mar). Q2: June 15, 2026 (covers Apr-May). Q3: September 15, 2026 (covers Jun-Aug). Q4: January 15, 2027 (covers Sep-Dec). All four 2026 dates fall on weekdays so no weekend/holiday shift applies. The "quarters" are not calendar quarters — Q2 is two months, Q3 is three months. See the deadline page for the full schedule.

What happens if I miss a quarter?

You owe the §6654 underpayment penalty — daily interest at the IRS short-term federal rate plus 3 percentage points, computed from the missed due date until the date you actually pay (or April 15, 2027, whichever is earlier). The rate resets each calendar quarter. For 2026 the combined rate is in the 7-8% APR range. A $5,000 missed Q1 trued up at filing is roughly $380 of penalty interest — annoying but not catastrophic. Consistent missing is structurally expensive.

Does W-2 withholding count toward the safe harbor?

Yes — and it counts as if it were paid evenly across all four quarters by default, even if your employer concentrated withholding late in the year. This is a quirk of IRC §6654(g). So if you have a W-2 plus 1099 income, increasing your W-2 withholding via a new W-4 is a way to cure underpayment retroactively — a tactic estimated-payments alone cannot match.

Can I pay all the safe-harbor amount in Q1 and skip Q2-Q4?

Yes — overpaying early always cures underpayment because the penalty stacks per-quarter. Paying $X in Q1 against a $X/4 quarterly minimum credits $3X/4 of "advance payment" forward through the year. Many freelancers with savings prefer to front-load to be done with it. The calculator does not enforce equal quarters; it just shows the per-quarter minimum.

How do I actually pay — Form 1040-ES, Direct Pay, or EFTPS?

Three options, all equivalent for safe-harbor purposes. IRS Direct Pay is the fastest — pay from a bank account, no fee, instant confirmation. EFTPS is the older system; required for some businesses, optional for most individuals. Form 1040-ES is the paper voucher route — print, write a check, mail. Pick whichever you will actually use four times in a year.

Do I need to pay state estimated taxes too?

Most states with an income tax mirror the federal safe harbor with their own quarterly schedule. California, New York, and several others have different deadlines or weighting rules — check your state taxing authority. This calculator only handles the federal §6654 safe harbor; state estimates are a separate calculation.

What if I'm new to self-employment and have no prior-year tax?

No prior-year return = no prior-year safe-harbor path. You are stuck with the 90%-current-year path, which means you have to forecast 2026 tax with reasonable accuracy. Most first-year freelancers err on the side of overpaying — the IRS will refund the overage at filing, but the underpayment penalty cannot be retroactively waived (except in narrow casualty/death exceptions per §6654(e)(3)).

Does this calculator handle SE tax, or just income tax?

Both, indirectly. The "prior-year total tax" input is your combined 2025 federal tax liability — Form 1040 Line 24 — which already includes SE tax (Schedule SE rolls through Schedule 2 into Line 23 of the prior 1040). Same for the current-year projection. So the safe-harbor minimum the calculator outputs covers both taxes at once. For SE-tax-only sizing, use the 1099 SE tax calculator.

Six mistakes that trigger the §6654 penalty

  • Confusing tax owed at filing with quarterly liability

    The §6654 minimum is based on prior-year total tax (Form 1040 Line 24), not the amount you wrote a check for at last filing. If you had withholding, the line-24 number is bigger than what you actually paid in April. Use the right line.

  • Missing the 110% threshold at $150,000 prior-year AGI

    A common surprise: cross $150k AGI and the prior-year safe-harbor multiplier flips from 100% to 110%. On a $30,000 prior-year tax bill that is an extra $3,000 spread across four quarters. Worth knowing in advance, not discovering at the Q3 deadline.

  • Using calendar quarters instead of the §6654 schedule

    Q2 covers Apr-May (not April-June). Q3 covers Jun-Aug (not July-September). People who set calendar reminders for "end of June" for Q2 miss the Jun 15 due date by two weeks. The deadlines are Apr 15, Jun 15, Sep 15, Jan 15 — set those exact dates.

  • Treating the underpayment penalty as a fixed fee

    It is not. It is daily interest from the missed due date until the payment lands. Pay one day late = pay one day of interest. Pay nine months late = pay nine months. Cheap to cure quickly, expensive to ignore.

  • Skipping state estimated payments

    States usually have their own §6654 equivalent and their own deadlines. New York and California are not aligned with the federal schedule. Federal safe harbor does not protect against state penalties.

  • Not increasing W-2 withholding when income spikes mid-year

    If you have a W-2, mid-year withholding bumps via a new W-4 are credited evenly across quarters, retroactively. Estimated payments only credit when made. So the W-4 lever can rescue you from a Q1/Q2 underpayment that estimated payments alone cannot fix.

Keep going

Sources

Last reviewed
Tax year
2026
Rule-module version
us.2026.v1

Author: Marcus Hale · United States tax analyst · Methodology

Estimation tool only — not professional tax advice. Consult a qualified tax advisor for your specific situation.