What you must have paid by each 2026 IRS installment date - and what the gap is already costing you at 7%.
| Your safe harbor | — |
|---|---|
| Safe harbor for the full year | — |
| Per installment | — |
| Must have been paid by this date | — |
| Counted as paid | — |
| Shortfall at this installment | — |
| Penalty running at 7% to Apr 15, 2027 | — |
| Pay by this date to be current | — |
| Verdict | — |
This page is the working piece. The full pack has everything below.
What you must have paid by each 2026 IRS installment date - and what the gap is already costing you at 7%.
A CPA package with quarterly estimate reviews runs $1,300-$2,500 a year; CPA compliance time bills $150-$250 an hour (2026 published rates).
Buy the full version — $60· ReadyStack
Real numbers from this tool, line by line.
$8,850 short at the September 15 installment - US freelancers and 1099 contractors with uneven income.
That is the checker's actual output for an ordinary case: 2025 tax $18,000, 2025 AGI $165,000, expected 2026 tax $24,000, with $3,000 paid in April and $3,000 in June.
| Result | |
|---|---|
| Your safe harbor | 110% of your 2025 tax (2025 AGI above $150,000) |
| Safe harbor for the full year | $19,800.00 |
| Per installment | $4,950.00 |
| Must have been paid by this date | $14,850.00 |
| Counted as paid | $6,000.00 |
| Shortfall at this installment | $8,850.00 |
| Penalty running at 7% to Apr 15, 2027 | $359.82 |
| Pay by this date to be current | $8,850.00 |
| Verdict | Short $8,850.00 at September 15, 2026. Each period is tested on its own, so paying the balance later does not undo this one. |
Now the two things that produced that number, because neither is the version most summaries give you.
The bar is not always 100%. The safe harbor everyone quotes is: pay 100% of last year's tax and you cannot be penalised. That is true, with something left out. If your 2025 AGI was above $150,000 ($75,000 if you file married filing separately), the number is not 100% - it is 110%. On an $18,000 2025 tax bill that is $1,800 of extra required payment that most summaries never mention.
The safe harbor is not an annual test. IRS Form 2210 tests each of the four periods separately. So you can pay your entire year's tax - the full 110%, every dollar of it - as one payment in January, and still be penalised for Q1, Q2 and Q3, because each of those installments was short on its own due date. The penalty is computed like interest: it runs on each underpaid installment for the number of days it stayed unpaid, at the underpayment rate the IRS has held at 7% for 2026.
That is where the $359.82 in the table comes from. The $8,850 gap sits unpaid from September 15, 2026 to April 15, 2027, and 7% runs against it for every one of those days. Paying the balance in January does not undo it.
The 2026 dates are April 15, June 15, September 15, and January 15, 2027 - all four fall on weekdays, so nothing shifts.
There is a way out if your income genuinely arrived late in the year: the annualized income installment method on Schedule AI recalculates the required installments against when you actually earned the money, and it can erase Q1-Q3 penalties entirely. It is worth knowing before you assume the penalty is fixed.
The checker takes your 2025 tax and AGI, your expected 2026 tax and what you have paid, and returns the safe harbor that applies to you, the dollar required by the installment date you pick, the shortfall, and the penalty already running on it.
Every installment date is free - all four periods, no key, no limit, and the answer is never locked. $60 once adds the next job: the schedule and penalty figures exported as a .csv you keep, and reminders 30, 14 and 1 day before each date. Yardstick: a CPA package with quarterly estimate reviews runs $1,300-$2,500 a year, and CPA compliance time bills $150-$250 an hour on 2026 published rates.
You enter your 2025 tax and AGI, your expected 2026 tax, and what you have paid so far. It returns the safe harbor that applies to you, the cumulative dollar that must have been paid by the installment date you picked, the shortfall, and the penalty already accruing at the 7% rate the IRS set for 2026.
US freelancers, 1099 contractors, consultants and S-corp owners whose income arrives unevenly, and the bookkeepers who handle them. If your income is a steady W-2 with withholding, you almost certainly do not need this. If your big month was June or December, you do.
The IRS page lists the four 2026 dates and the rule; it does not tell you the dollar you are short right now. Chatbots routinely repeat pay 100% of last year and drop the $150,000 AGI trigger that makes it 110%, and they treat the year as one total when Form 2210 tests each period on its own.
The whole calculation is free, for all four periods, with no key, no watermark and no usage limit. The $60 licence adds two things on a different axis: exporting the schedule and penalty figures as a .csv you keep, and browser reminders 30, 14 and 1 day before your installment date.
A solo or small-firm CPA package that includes quarterly estimate reviews is commonly $1,300-$2,500 a year, and CPA compliance time bills at $150-$250 an hour on 2026 published rates. The penalty this is built to catch is often larger than either, because it compounds daily from each missed date.
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