Quarterly Estimated Tax Calculator
A quarterly estimated tax calculator helps plan federal estimated payments from your projected annual tax, withholding, and eligible prior-year tax figures. This 2026 tool compares the regular current-year and prior-year payment targets, then shows an equal-installment schedule. It does not calculate your income tax return or determine a late-payment penalty.
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Report a calculation issue Quarterly Estimated Tax Calculator: purpose and method
A quarterly estimated tax calculator helps plan federal estimated payments from your projected annual tax, withholding, and eligible prior-year tax figures. This 2026 tool compares the regular current-year and prior-year payment targets, then shows an equal-installment schedule. It does not calculate your income tax return or determine a late-payment penalty.
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Method and test recordFormula v1.0.1
- Recorded scope
- Not recorded
- Publisher
- CalculatorGeek
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- CalculatorGeek Editorial Team
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- Not recorded
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- Not scheduled
- Definition fixtures
- 6 configured scenarios
- Published examples
- 6 shown below
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No tool-specific review method has been recorded.
These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy
Known limitations
Method sources
Latest model update
2026-10-28 - Created from finished package copy and deterministic contract.
Reference inputs and expected results
Up to 12 examples from the configured definition fixtures are shown. Expected values use the stated output units; invalid inputs are intended to be rejected.
| Case | Inputs | Expected result |
|---|---|---|
| High-AGI prior safe harbor | Current Tax: 30000; Prior Tax: 24000; Prior Agi: 180000; Mfs: false; Prior Eligible: true; Withholding: 6000 | Current Tax: 30000; Prior Tax: 24000; Prior Agi: 180000; Withholding: 6000; Required Annual: 26400; Annual Installments: 20400; Quarterly: 5100; Year End Balance: 3600 (allowed numeric tolerance: 1.0E-6) |
| Below $1,000 remaining tax | Current Tax: 12000; Prior Tax: 10000; Prior Agi: 100000; Mfs: false; Prior Eligible: true; Withholding: 11200 | Planned Estimates: 0; Equal Installment: 0; Projected Filing Balance: 800 (allowed numeric tolerance: 1.0E-6) |
| Third-period cumulative amount | Annual Planned Estimates: 20400; Installment: 3; Estimated Payments To Date: 10000 | Cumulative Target: 15300; Additional Cumulative Needed: 5300 (allowed numeric tolerance: 1.0E-6) |
| Prior method unavailable | Current Tax: 10000; Prior Eligible: false; Withholding: 0 | Required Annual: 9000; Planned Estimates: 9000; Equal Installment: 2250; Projected Filing Balance: 1000 (allowed numeric tolerance: 1.0E-6) |
| Qualifying zero-prior-tax exception without required prior return | Current Tax: 10000; Withholding: 0; Prior Return Filed: false; Prior Zero Tax Exception Verified: true | Required Annual: 0; Planned Estimates: 0; Baseline Plan Balance: 10000 (allowed numeric tolerance: 1.0E-6) |
| Actual estimates exceed planned target | Current Tax: 30000; Withholding: 6000; Planned Estimates: 20400; Actual Estimates And Applied Credits: 25000 | Baseline Plan Balance: 3600; Projected Final Balance With No More Payments: -1000 (allowed numeric tolerance: 1.0E-6) |
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Gather the correct tax figures
Enter projected 2026 total federal tax after the credits used in the estimated-tax worksheet, but before withholding and estimated payments. For 2026, this is worksheet line 11c, already net of the line 11b refundable credits. Include applicable self-employment and other taxes in that projection. Do not enter gross income, taxable income, or only the balance due on last year's return.
For the prior-year method, use the 2025 tax amount figured under page 8 of the 2026 IRS instructions, before applying the 100% or 110% factor, along with prior-year adjusted gross income and your current filing-status category. Confirm that the prior return covered 12 months and that the prior-year method applies. The verified no-prior-tax exception is separate: it can apply when no prior return was required if the citizen/resident and full-year conditions are met. A missing return alone does not establish that exception.
Enter expected annual federal withholding from all relevant sources. Withholding is different from estimated payments already sent. Keep those prior estimated payments in their own field so the calculator can compare them with the cumulative target through a selected installment.
How the regular payment target works
Under the general rules in IRS Publication 505, estimated payments may be required when you expect to owe at least $1,000 after withholding and credits and withholding falls below the applicable payment target. The ordinary annual target compares 90% of current-year tax with 100% of eligible prior-year tax.
The prior-year percentage is generally 110% when prior-year adjusted gross income exceeds $150,000, or $75,000 for married filing separately. The calculator subtracts expected withholding from the smaller applicable annual target and divides the remaining amount into four equal planned installments.
This is the regular equal-installment method. Farmers, fishers, uneven-income annualization, certain filing-status changes, disaster relief, and other special situations may need different treatment. Meeting an estimated-payment target does not mean that no balance will be due when you file.
Example: safe-harbor payments and a remaining tax balance
Assume projected 2026 tax is $30,000, eligible 2025 tax is $24,000, prior-year AGI is $180,000, and the taxpayer is not married filing separately. Expected annual withholding is $6,000.
| Calculation | Result |
|---|---|
| 90% of current projected tax | $27,000 |
| 110% of eligible prior-year tax | $26,400 |
| Smaller annual payment target | $26,400 |
| Less expected withholding | $6,000 |
| Planned estimated payments for the year | $20,400 |
| Four equal planned installments | $5,100 each |
If the final tax really is $30,000, paying $20,400 in estimates plus $6,000 in withholding leaves $3,600 due at filing. That is why the payment target and the final tax bill should be shown separately. Timeliness and the accuracy of the inputs still matter.
2026 regular installment dates
The ordinary 2026 schedule listed in IRS Publication 505 is April 15, June 15, September 15, 2026, and January 15, 2027. These are not four evenly spaced three-month intervals. Check for relief or special rules that apply to your location or circumstances.
If you are checking the third installment, the equal-installment cumulative target is three-fourths of the planned annual estimated payments. Subtract qualifying estimates and credits allocated through that point. Paying a catch-up amount later does not necessarily remove an earlier-period underpayment penalty.
Use the result in your cash plan
Update the projection when income, deductions, credits, or withholding changes. If your income is seasonal, a regular four-way split may differ from an annualized-income calculation. Keep records of payment dates and amounts, and reconcile the estimate with the actual return. The baseline filing balance assumes you pay the planned annual total; payments already made above that target must also be credited when assessing a possible overpayment.
For business budgeting, the business loan calculator can show debt payments as a separate cash commitment. Those payments are not automatically a tax deduction. If retirement withdrawals affect your income or withholding, the retirement withdrawal calculator can help model the spending side while the tax projection handles tax treatment.
Frequently asked questions
Should I divide my self-employment tax by four?
That alone is incomplete. Federal estimated payments can also cover income tax and other taxes, while withholding, credits, and safe-harbor rules can reduce the payment needed.
Is prior-year tax the amount I paid with the return?
No. The balance due after withholding and estimates is different from the tax figure used by the safe-harbor worksheet. Use the amount defined in the IRS instructions.
Does a safe harbor eliminate all tax due at filing?
No. It concerns the required payment target under the applicable rules. Your final tax can exceed the target, as the example shows.
Can this tool calculate a penalty for a late installment?
No. It shows a planning target and cumulative difference. Actual underpayment calculations depend on dates, amounts, withholding treatment, exceptions, and applicable IRS rates.
Enter the worksheet tax figures and expected withholding, then review the installment plan and possible filing balance together.