Your safe harbor, your payment history and the installments that are actually still ahead of you — as of today, not as of a blank January.
Quick answer
This builds the Form 2210 ledger for your year: what each installment required, what your payments and withholding covered by each due date, and what is left. Installments whose due date has passed are shown as history — paid, underpaid or past due — and never as payments to make.
What this includes
The 90%-of-current-year and 100%/110%-of-prior-year safe harbors, and which one governs
Every payment you have made, credited to the earliest installment still short
Withholding treated as paid in four equal amounts, or on the dates it happened under the Form 2210 box D election
The annualized income installment method, including Schedule AI Part II's prorated Social Security wage base
Farmers and fishers: one installment, 66⅔%, and the March 1 filing alternative
A short prior year, or no prior return, removing the prior-year method entirely
What it excludes
The dollar penalty itself — that needs the federal short-term rate for each quarter the shortfall ran
State estimated tax, which has its own dates and its own safe harbors
Annualizing the Net Investment Income Tax or the Additional Medicare Tax, which Schedule AI line 16 asks for separately
Fiscal-year filers, whose due dates are computed from their own year end
The 2026 rule most people get wrong: Dividing your annual target by four is not penalty-safe once an installment has been missed. The penalty in IRC § 6654 is charged period by period, so a shortfall on 15 April keeps accruing even after the year's payments add up correctly — and only extra withholding, not another payment, can reach back and cover it.
🔒Private by design. No SSN, no bank login, no IRS login, no payroll password. No account is required. Calculator inputs are processed locally in your browser and are not transmitted to or stored by TaxSaveIQ. Standard website analytics and technical logs may still apply. See our Privacy Policy. Educational estimate only.
When are you planning from?
Defaults to today. Installments whose due date has passed are shown as history, never as payments to make.
Expected 2026 income
$
Income your employer withholds from
$
After business expenses
$
Interest, dividends, retirement
Withholding
$
Federal income tax, from any source
$
From your remaining paychecks or distributions
The default is what the law assumes and is usually better. The election requires you to file Form 2210.
Payments already made
Enter the date and amount of each payment. A payment is credited to the earliest installment still short, not to the quarter you sent it in — so a late payment clears the one you missed and leaves the current one open.
$
$
$
$
Last year's return
$
Form 1040 line 24 — drives the safe harbor
$
Line 11 — decides 100% vs 110%
Filing separately halves the threshold to $75,000
A short prior year removes the prior-year safe harbor
One installment instead of four, and 66⅔% instead of 90%
Method
Annualizing matches each installment to the income you had actually received by then
Your safe harbor
Safe-harbor target
$18,000
Pay by Sep 15
$4,500
Expected total tax for 2026$32,660
Form 1040 line 24, including self-employment tax
Self-employment tax inside that$16,955
Current-year method (90% of this year)$29,394
Prior-year method (100% of last year)$18,000
Safe-harbor target$18,000
The lesser of the two — the prior-year method governs
Withholding credited$0
Payments made$0
Still to pay across remaining installments$9,000
Your 2026 installment schedule
Due
Status
Required
Credited
Action
Apr 15
Jan 1 – Mar 31
Past due
$4,500
$0
$4,500 short
Jun 15
Apr 1 – May 31
Past due
$4,500
$0
$4,500 short
Sep 15
Jun 1 – Aug 31
Due next
$4,500
$0
Pay $4,500
Jan 15
Sep 1 – Dec 31
Future
$4,500
$0
Pay $4,500
As of 2026-08-05. 2 of 4 installments still ahead.
Two ways to close the $9,000 you have missed
Catch-up payment now$9,000
Credited on the day you send it. Stops further penalty from today, but the periods already missed keep what has accrued.
Extra withholding instead$18,000
Larger, because only $9,000 of it lands on the periods you missed — the rest reduces the installments still ahead. Total still to pay this year is $18,000 either way.
You are $9,000 short across installments that have already fallen due. The underpayment penalty in IRC § 6654 is charged period by period, so paying the year's full safe-harbor amount over the installments that remain does NOT undo it — the shortfall keeps accruing until it is covered.
Increasing withholding on a paycheck or a retirement distribution is the one instrument that reaches backwards: it is treated as paid in four equal amounts on the four due dates regardless of when it was actually withheld, so $9,000 of a $18,000 increase is credited to the installments you have already missed. An estimated payment is credited on the day you send it and cannot do that. Neither route costs more in total — the year needs the same money either way — but the withholding route stops the penalty clock on the earlier periods.
Only 2 of the four 2026 installments are still ahead of you, so dividing your annual target by four is the wrong arithmetic today. The figures below spread what is left over the installments that actually remain.
These installments assume your income arrives evenly. If it does not — a bonus, a property sale, a seasonal business — the annualized income installment method can lower the early installments. Switch the method above to see the difference.
This schedule shows what was required and what was credited. It does not compute the dollar penalty, which is charged at the federal short-term rate plus three points and changes every quarter — Form 2210 or an IRS notice will produce that figure.
The 2026 installments
They are called quarterly and they are not. The second installment covers two months, the third covers three, and the fourth covers four and is due in the following January. If a date ever falls on a weekend or a legal holiday it moves to the next business day — none of the 2026 dates does.
Installment
Income period
Due
Schedule AI factor
Cumulative requirement
Q1
Jan 1 – Mar 31
April 15, 2026
× 4
22.5%
Q2
Apr 1 – May 31
June 15, 2026
× 2.4
45.0%
Q3
Jun 1 – Aug 31
September 15, 2026
× 1.5
67.5%
Q4
Sep 1 – Dec 31
January 15, 2027
× 1
90.0%
The last two columns are the annualized method's. Income through 31 March is multiplied by four to estimate the year, and 22.5% of the resulting tax is what that installment must cover. Under the regular method every installment is simply 25% of the annual target instead.
What the safe harbor comes to at different income levels
A single filer whose only income is Schedule C net profit, with no withholding, planning from 2026-04-01 — before the first installment, so all four are still ahead. Last year is assumed to have been 80% of this year, which is what makes the prior-year method the smaller number in most rows. Computed by the same functions the calculator above uses.
Net profit
Total tax
90% of this year
Prior-year method
Safe harbor
Per installment
$30,000
$5,417
$4,875
$4,012100% of last year
$4,012prior year
$1,003
$60,000
$12,989
$11,690
$9,955100% of last year
$9,955prior year
$2,489
$100,000
$25,745
$23,171
$18,830100% of last year
$18,830prior year
$4,708
$150,000
$43,385
$39,047
$32,660100% of last year
$32,660prior year
$8,165
$250,000
$76,424
$68,781
$67,738110% of last year
$67,738prior year
$16,935
Watch the fourth column change percentage as income rises. Once prior-year AGI passes $150,000 the prior-year test becomes 110% rather than 100%, and at that point it can stop being the cheaper of the two — which is the moment the current-year method starts governing and your target falls rather than rises.
Two rules that decide whether you owe a penalty
The penalty is charged per period, not per year
This is the rule that catches people out. Paying the full safe-harbor amount by the following April does not undo a missed 15 April installment: IRC § 6654 computes an underpayment for each period separately and charges interest on each from its own due date. A taxpayer who paid nothing until December and then paid everything can still owe a penalty on three periods.
It follows that the arithmetic changes as the year runs. In January, four equal payments work. In August, with two dates gone, dividing the remaining target by four is simply the wrong sum — and dividing by two is right only for what is left, not for what was missed. That is why the schedule above separates the two.
Withholding is credited evenly, whenever it happened
Federal income tax withheld from wages, a pension or an IRA distribution is treated under IRC § 6654(g) as paid in four equal amounts on the four due dates, no matter when it was actually withheld. A withholding increase in November is therefore credited a quarter each to April, June, September and January — it reaches backwards, and an estimated payment does not.
That makes a late-year withholding bump the standard fix for someone who is behind, and it is why a retiree can leave withholding off their distributions all year and take one large withheld distribution in December. It also means the reverse election — Form 2210 box D, crediting withholding on the dates it really happened — only helps if your withholding was front-loaded, and it commits you to filing Form 2210.
Neither route is cheaper in total. The year needs the same money either way; what changes is which periods it is treated as covering, and therefore how much interest accrues.
When you can ignore all of this
✓Your balance due after withholding and refundable credits will be under $1,000. The penalty generally does not apply at all.
✓You had no tax liability at all in a prior year that covered a full 12 months, and you were a US citizen or resident for the whole of it.
✓Your prior-year AGI was at or below $150,000 ($75,000 filing separately) and your withholding alone already reaches 100% of last year's total tax.
✓You are a farmer or fisher and you file your return and pay the tax in full by March 1, 2027. No installment is required at all.
Frequently asked questions
What are the 2026 quarterly estimated tax due dates?
April 15, June 15 and September 15 of 2026, then January 15 of 2027. None of those four dates falls on a weekend or a federal holiday this year, so none shifts. They are not evenly spaced: the second installment covers only April and May, which is why the year's payments are not really quarters.
How much should a 1099 worker pay each quarter?
Enough that the year's payments reach a safe harbor — the lesser of 90% of this year's total tax or 100% of last year's, and 110% of last year's if your prior-year AGI was over $150,000 ($75,000 filing separately). Divide that by four only if the year has not started. Partway through, divide what is still needed by the installments that are actually left, which is what the schedule on this page does.
I missed the April payment. Can I just pay more later?
Not without a penalty. The IRC § 6654 penalty is computed per period, so a shortfall on 15 April keeps accruing until it is covered even if the year's total ends up correct. There is one instrument that reaches backwards: withholding is treated as paid in four equal amounts on the four due dates whenever it actually happened, so raising withholding on a paycheck or a retirement distribution can cure an earlier installment. An estimated payment cannot.
What is the 110% safe harbor and does it apply to me?
If your PRIOR-year adjusted gross income exceeded $150,000 — $75,000 if you filed separately — the prior-year safe harbor is 110% of last year's total tax rather than 100%. The test looks at last year's AGI, not what you expect to earn this year, so a large current year does not push you to 110% and a large previous year does even if this year is small.
Does withholding count toward my quarterly payments?
Yes, and generously. Federal income tax withheld from wages, pensions or IRA distributions is credited toward the same safe harbor as estimated payments, and it is treated as paid in four equal amounts across the year regardless of when it was withheld. That timing rule is why a taxpayer who is behind is often better off raising withholding than sending a cheque.
What is the annualized income installment method?
It is the alternative on Form 2210, Schedule AI, that matches each required installment to the income you had actually received by the end of that period rather than assuming the year was flat. Someone whose income arrives in the fourth quarter can owe almost nothing for the first installment under it. It works — but you have to file Form 2210 with Schedule AI attached to claim it; the IRS will not apply it for you.
Is there an amount below which I can skip estimated payments?
If your balance due after withholding and refundable credits will be under $1,000, the underpayment penalty generally does not apply at all. There is a second exception for anyone who had no tax liability in a prior year that covered a full 12 months, provided they were a US citizen or resident for the whole of it.
How large is the penalty if I get this wrong?
It is interest, charged at the federal short-term rate plus three percentage points, running from each missed due date until the amount is paid. This page does not compute the dollar figure, because the rate changes every quarter and the arithmetic needs the rate for each quarter the shortfall ran. Form 2210 or an IRS notice will produce it.
Pay through IRS Direct Pay or EFTPS— both are free and both give you a confirmation number, which is the record you will want if a period is ever questioned. If you would rather not deal with vouchers at all, the W-4 optimizer sizes the payroll equivalent.
Educational estimate only. This is a federal planning estimate. It reconstructs the Form 2210 ledger from what you enter but does not compute the penalty, does not cover state estimated tax, and cannot see payments you have not told it about. Your own records and an IRS transcript are the authority on what has been credited. Full disclaimer.