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HomeLegal & BusinessQuarterly Tax Calculator

Quarterly Tax Calculator

Calculate your quarterly estimated tax payments to avoid IRS underpayment penalties. Supports current-year and safe harbor methods.

Auto-updated May 11, 2026 · Verified daily against IRS, Fed & Treasury sources

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Quarterly Tax Calculator

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Assumptions· 2026

  • ·Estimated quarterly payments due: April 15, June 16, Sept 15, Jan 15 (2026 schedule)
  • ·Safe harbor: 100% of prior-year tax (110% if prior-year AGI > $150k) avoids underpayment penalty
  • ·Self-employment income subject to SE tax (15.3% on 92.35% of net earnings, IRC §1401)
  • ·Quarterly installment = annual estimated tax ÷ 4 (annualized income method also shown)
When this is wrong
  • ·Underpayment penalty rate: 8% APR (2026 IRS rate) on any shortfall below safe harbor
  • ·Annualized income installment method (Form 2210 Schedule AI) for uneven income — reduces overpayment
  • ·State estimated tax requirements — most states have separate quarterly schedules
  • ·Withholding from W-2 counts toward estimated tax — adjust quarterly payment for side income only
Assumptions· 2026▾
  • ·Estimated quarterly payments due: April 15, June 16, Sept 15, Jan 15 (2026 schedule)
  • ·Safe harbor: 100% of prior-year tax (110% if prior-year AGI > $150k) avoids underpayment penalty
  • ·Self-employment income subject to SE tax (15.3% on 92.35% of net earnings, IRC §1401)
  • ·Quarterly installment = annual estimated tax ÷ 4 (annualized income method also shown)
When this is wrong
  • ·Underpayment penalty rate: 8% APR (2026 IRS rate) on any shortfall below safe harbor
  • ·Annualized income installment method (Form 2210 Schedule AI) for uneven income — reduces overpayment
  • ·State estimated tax requirements — most states have separate quarterly schedules
  • ·Withholding from W-2 counts toward estimated tax — adjust quarterly payment for side income only
Real-world example: Freelancer deciding between LLC and S-Corp▾

A Texas-based freelance graphic designer earns $140,000 net profit/year from client work. She's evaluating whether to stay as a sole proprietor, form an LLC, or elect S-Corp status to reduce self-employment taxes.

  • Net business profit: $140,000
  • Sole prop SE tax (15.3%): ~$19,800
  • S-Corp reasonable salary: $75,000
  • SE tax on salary portion: ~$11,475
  • S-Corp distribution (no SE tax): $65,000
Annual SE tax savings via S-Corp
~$8,300/yr

Takeaway: S-Corp saves $8,300/year but adds ~$1,500-$3,000 in accounting fees (payroll, extra returns). Break-even is around $80-90K net profit. Below that, the overhead eats the savings. Texas has no state income tax, so the benefit is purely federal SE savings.

When this calculator is wrong▾
  • Entity structure recommendations depend on state law

    LLC annual fees range from $0 (Ohio) to $800 minimum (California, even for zero-revenue LLCs). Delaware C-Corp is standard for VC-backed companies but adds registered agent costs (~$300/yr) for out-of-state entities. The "best" structure is state-specific.

  • S-Corp election has eligibility requirements

    S-Corps cannot have more than 100 shareholders, cannot have non-US shareholders, and cannot have corporate shareholders. Violating these rules (e.g., adding a foreign investor) terminates S-Corp status retroactively, potentially creating a large unexpected tax event.

  • Reasonable compensation determination is subjective

    The IRS requires S-Corp owner-employees to pay themselves a "reasonable salary" before taking distributions. There is no fixed formula — the IRS looks at industry benchmarks, duties, and hours worked. Setting the salary too low is a common audit trigger for S-Corps.

  • Break-even calculations exclude time cost

    Business break-even models track revenue vs. direct costs. They rarely factor in the owner's time as a cost. If you're working 60 hours/week at imputed $50/hour, your "profitable" business may be paying you $12/hour after the opportunity cost calculation.

    Break-Even Calculator
  • Business valuation methods produce different results

    A service business valued on EBITDA multiples (2-4×) gets a very different number than one valued on SDE (seller's discretionary earnings) or discounted cash flow. Buyers and sellers typically use different methods to argue their preferred price. This calculator uses a single method.

    Business Valuation Calculator

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AI Savings Calculator →Break-Even Calculator →Business Expense Tracker →
Your Results

Based on your inputs

ℹ️Demo numbers — replace inputs to see yours
Quarterly Payment
$4,388positive

per quarter

Q1 Due — April 15$4,388
Q2 Due — June 15$4,388
Q3 Due — Sept 15$4,388
Q4 Due — Jan 15$4,388
Estimated Total Tax$19,501
SE Tax Component$11,304

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Q1 (Jan–Mar): April 15. Q2 (Apr–May): June 15. Q3 (Jun–Aug): September 15. Q4 (Sep–Dec): January 15 of the following year.

Pay either 100% of last year's tax liability (110% if AGI > $150k) OR 90% of this year's expected tax. The safe harbor method uses prior year's liability.

The IRS charges an underpayment penalty (currently ~8% annualized). Pay as soon as possible to minimize the penalty.

Yes if you expect to owe $1,000+ after subtracting withholding. W-2 employees with side income may also need to make estimates.

You avoid penalties by paying at least 100% of last year's tax liability (110% if AGI exceeded $150,000) or 90% of current year's tax, whichever is less.

Technically yes, but you may owe underpayment penalties for the earlier quarters you missed. The IRS expects roughly equal quarterly payments. The annualized income installment method can reduce penalties for uneven income.

Pay online at IRS.gov/payments using Direct Pay or EFTPS. You can also mail Form 1040-ES with a check. Most states have separate estimated tax systems requiring additional payments.

This method calculates estimated tax based on income actually earned in each quarter rather than dividing the annual estimate by four. It benefits freelancers with seasonal or uneven income patterns.

Yes. Most states with income tax require separate estimated tax payments on their own schedule. Some states follow the federal due dates; others have different deadlines and forms.

Project your annual income and deductions, then calculate self-employment tax and income tax on that estimate. Divide the total by four for equal payments. Adjust each quarter as actual income becomes clearer to avoid overpaying or underpaying.

Current Year: Pay 90% of expected tax ÷ 4

Safe Harbor: Pay 100% of prior year tax ÷ 4

Published byJere Salmisto· Founder, CalcFiReviewed byCalcFi EditorialEditorial standardsMethodologyLast updated May 12, 2026

Primary sources & authoritative references

Every formula on this page traces to a federal agency, central bank, or peer-reviewed institution. We cite the rule-makers, not secondhand blogs.

  • USA.gov — Money and consumer protection — U.S. General Services Administration (opens in new tab)

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Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.