Quarterly Estimated Tax Calculator
Estimate 2026 U.S. federal tax, compare safe-harbor targets, and spread the remaining amount across active Form 1040-ES due dates.| Payment | Income period | Due date | Planned amount | Cumulative target | Copy |
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Governing target
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Quarterly estimated tax is not a bill for four equal three-month quarters. It is a way to prepay federal tax when withholding will not cover enough of the year's liability, commonly because of self-employment, investment, rental, or other income. The regular payment periods end March 31, May 31, August 31, and December 31, so their lengths are uneven.
Two annual targets answer different questions. Full projected tax is a cash-flow target intended to reduce the balance left for filing. Required annual payment is the smaller safe-harbor amount after the relevant current-year, prior-year, withholding, and under-1,000 tests. Paying a safe-harbor amount may reduce underpayment-penalty exposure while still leaving tax due with the return.
| Planning question | Relevant figure | Important limit |
|---|---|---|
| What might the year cost? | Projected total federal tax | Depends on complete income, deduction, credit, and special-tax inputs. |
| What minimum is modeled? | Required annual payment | A minimum can leave a filing balance. |
| What remains to schedule? | Selected target less withholding and estimates already paid | Earlier missed installments and penalties are not calculated. |
| When is it due? | Active Form 1040-ES dates | Weekend, holiday, fiscal-year, or special-rule timing may differ. |
Self-employment income affects both income tax and self-employment tax. Net profit is reduced to 92.35% for the Schedule SE planning base. Social Security tax applies only to the remaining annual wage-base room after W-2 wages, Medicare tax has no wage-base cap, and Additional Medicare tax can apply above a filing-status threshold. Half of regular self-employment tax is then deducted when estimating adjusted gross income.
Withholding is especially important because it reduces the amount left under both safe-harbor and full-tax planning. Estimated payments already made also reduce the remaining schedule, but the model does not decide whether a late payment satisfies an earlier installment. Income arriving unevenly during the year may require the annualized income installment method instead of a simple equal split.
Some tax items cannot be approximated safely with ordinary-income brackets alone. Qualified dividends, capital gains, net investment income tax, alternative minimum tax, retirement contributions, itemized-deduction limits, credit phaseouts, and the full qualified business income (QBI) deduction can materially change the return. State and local estimated taxes are separate.
This is a 2026 U.S. federal planning estimate, not tax advice or filing software. Use the current Form 1040-ES and its recent developments, and seek professional review when income is uneven, international, investment-heavy, partnership-based, or affected by special elections.
How to Use This Tool:
Build the annual tax estimate first, then choose whether the payment schedule should target the safe-harbor minimum or the full modeled tax.
- Choose the expected Filing status and First payment period. Use the farming or fishing option only when the special two-thirds rule applies to the taxpayer.
- Select Full projected federal tax to plan toward the modeled liability, or Required annual payment to use the modeled safe-harbor minimum.
- Enter annual net self-employment profit after business expenses, annual Medicare wages, and other income that should be taxed at ordinary rates. Do not place gross business receipts or preferential-rate gains in the ordinary-income fields.
- Choose the standard or manual itemized deduction and decide whether to omit QBI or use the simplified 20% estimate. Enter only credits supported by a separate estimate.
- Add expected federal withholding, 2026 estimates already paid or credited, prior-year total tax, and the applicable prior-year rule. If there is no qualifying 12-month prior-year amount, choose the no-prior-year option.
- Use Advanced for independently calculated adjustments, alternative minimum tax, other federal taxes, refundable credits, or a planning cushion. Clear every validation message and confirm the active due dates before using the payment amount.
Interpreting Results:
- Total estimated tax combines modeled income tax, self-employment tax, Additional Medicare tax, entered other taxes, and credits.
- Required annual payment becomes 0 when projected tax after withholding is less than 1,000 or withholding already covers the smaller safe-harbor target.
- Remaining target subtracts expected withholding and estimates already paid from the selected annual target, then floors the result at 0.
- Projected filing balance after this plan can remain positive under the required-payment target. That is expected when the safe harbor is lower than full projected tax.
- The schedule divides the remaining target across the selected active dates. It does not calculate late-payment penalties, interest, or an annualized-income schedule.
Technical Details:
The annual model has three stages. First it estimates self-employment and ordinary income tax. Next it constructs current- and prior-year safe-harbor targets. Finally it subtracts prepayments and spreads the selected remainder across the active 2026 Form 1040-ES dates.
Formula Core:
Let P be net self-employment profit, W Medicare wages, and T projected total federal tax. Monetary results are calculated to full working precision and then rounded to cents.
Self-employment net earnings below 400 are treated as 0 for this calculation. The deductible half of regular self-employment tax is half of the Social Security and 2.9% Medicare amounts; Additional Medicare tax is not included in that deduction. Additional Medicare tax is 0.9% of combined wages and self-employment net earnings above 200,000 for single or head of household, 250,000 for married filing jointly, or 125,000 for married filing separately.
Adjusted gross income subtracts the regular self-employment-tax deduction and entered adjustments from self-employment profit, wages, and other ordinary income. The selected standard or itemized deduction is then applied. The simplified QBI amount is the smaller of 20% of net self-employment profit and 20% of taxable income before QBI.
Lookup Core:
The ordinary-income calculation uses the following 2026 bracket ceilings. Income above the last listed ceiling continues at 37%.
| Rate | Single | Married joint | Married separate | Head of household |
|---|---|---|---|---|
| 10% | 12,400 | 24,800 | 12,400 | 17,700 |
| 12% | 50,400 | 100,800 | 50,400 | 67,450 |
| 22% | 105,700 | 211,400 | 105,700 | 105,700 |
| 24% | 201,775 | 403,550 | 201,775 | 201,750 |
| 32% | 256,225 | 512,450 | 256,225 | 256,200 |
| 35% | 640,600 | 768,700 | 384,350 | 640,600 |
| 37% | Above 640,600 | Above 768,700 | Above 384,350 | Above 640,600 |
| Filing status | Standard deduction | Additional Medicare threshold |
|---|---|---|
| Single | 16,100 | 200,000 |
| Married filing jointly | 32,200 | 250,000 |
| Married filing separately | 16,100 | 125,000 |
| Head of household | 24,150 | 200,000 |
Rule Core:
| Rule | Modeled amount | Boundary |
|---|---|---|
| Current-year target | 90% of projected total tax | Regular payment-period options. |
| Farming or fishing target | 66 2/3% of projected total tax | Special one-payment option only. |
| Prior-year target | 100% of prior-year total tax, or 110% when the high-income rule is selected | Requires a qualifying prior-year amount; 110% is not applied in farming/fishing mode. |
| Safe-harbor comparison | Smaller of current-year and prior-year targets | No-prior-year mode uses the current-year target. |
| Withholding test | Safe-harbor target − expected withholding | At 0 or less, required annual payment becomes 0. |
| Residual test | Total estimated tax − expected withholding | Below 1,000, required annual payment becomes 0; exactly 1,000 does not clear this test. |
The high-income 110% choice is generally associated with prior-year adjusted gross income above 150,000, or 75,000 for married filing separately. Eligibility is not inferred from the current-year inputs; the appropriate prior-year rule must be selected from the prior return.
| Payment | Income period | Due date |
|---|---|---|
| 1st | Jan 1–Mar 31, 2026 | Apr 15, 2026 |
| 2nd | Apr 1–May 31, 2026 | Jun 15, 2026 |
| 3rd | Jun 1–Aug 31, 2026 | Sep 15, 2026 |
| 4th | Sep 1–Dec 31, 2026 | Jan 15, 2027 |
| Farming/fishing | 2026 tax year | Jan 15, 2027 |
The remaining target is divided evenly in cents across the active payment rows, with any leftover cents assigned to the earliest rows. Whole-dollar display rounding changes presentation only. A planning cushion increases the selected annual target by the entered percentage; it is not an IRS safe-harbor rule.
Accuracy and Privacy Notes:
Tax rules and personal facts can change after a planning run. Confirm the figures with the current 2026 Form 1040-ES, applicable worksheets, and professional advice where warranted.
- The simplified QBI estimate omits business-type restrictions, income phaseouts, wage and property limits, losses, capital-gain limits, and other full Form 8995/8995-A rules.
- Capital gains, qualified dividends, net investment income tax, penalty calculations, state tax, and the annualized income installment method are not modeled.
- Alternative minimum tax and other federal taxes are accepted only as separately calculated inputs.
- Calculations use the amounts in the browser and do not send tax inputs to a server. Copied text, downloads, and screenshots can still expose sensitive income and filing details.
Worked Examples:
Full-tax plan with prior-year safe harbor
A single filer with 85,000 of net self-employment profit, 30,000 of wages, 8,000 of other ordinary income, the standard deduction, simplified QBI, 1,200 of nonrefundable credits, 5,200 of withholding, and 3,500 already paid has modeled total tax of 23,979. A prior-year total tax of 18,500 is the smaller safe-harbor target. With full projected tax selected before April, the remaining 15,279 is divided into four payments of 3,819.75.
High-income prior-year target
For a single filer with 100,000 of wages and 250,000 of net self-employment profit, 20,000 of withholding, 5,000 already paid, and 50,000 of prior-year tax under the 110% rule, the prior-year target is 55,000. The remaining required-payment target is 30,000, while the modeled filing balance remains 45,980.16 because projected total tax is much higher.
References:
- 2026 Form 1040-ES, Estimated Tax for Individuals, Internal Revenue Service, February 2026.
- Tax inflation adjustments for tax year 2026, Internal Revenue Service, October 9, 2025.
- Topic no. 554, Self-employment tax, Internal Revenue Service.
- Topic no. 560, Additional Medicare tax, Internal Revenue Service.
- Contribution and Benefit Base, Social Security Administration.