Why does the safe-harbor percentage change to 110%?

For taxpayers whose prior-year AGI exceeded $150,000, the IRS requires paying 110% of last year's tax (instead of 100%) to qualify for the safe harbor.

Why are the quarterly periods uneven?

The IRS's own Form 1040-ES schedule splits the year into periods of 3, 2, 3, and 4 months rather than four equal quarters.

Do I need to make the January payment?

No — you can skip it if you file your complete tax return and pay any remaining balance by February 1.

Does this include state estimated taxes?

No — this covers federal income tax and federal self-employment tax only.

Why is only half of my SE tax deductible?

The IRS treats the employer-equivalent half of the 15.3% regular SE tax as a business expense, deductible above the line — but the 0.9% Additional Medicare surtax is never deductible.

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Quarterly Estimated Tax Calculator

Quarterly IRS estimated tax payments for self-employment income, with safe-harbor guidance.

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Last reviewed 2026-08-30

About the Quarterly Estimated Tax Calculator

Estimates federal quarterly estimated tax payments for self-employment income — combining self-employment tax with a federal income tax estimate — and checks whether your planned payments meet the IRS safe-harbor threshold to avoid an underpayment penalty.

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How to use it

Enter your expected annual net self-employment income.
Enter your prior year's total tax liability and AGI, to check safe-harbor guidance.
Read your estimated quarterly payment, and the safe-harbor amount that avoids a penalty.

Formula

Self-employment tax follows the same calculation as the Self-Employment Tax Calculator (92.35% net-earnings factor, 12.4% Social Security up to the wage base, 2.9% Medicare, +0.9% Additional Medicare above $200,000). Half of the regular 15.3% SE tax is deducted above the line before computing federal income tax on the 2026 single-filer brackets with the standard deduction. Total estimated tax = federal income tax + SE tax; quarterly payment = total ÷ 4. Safe harbor annual payment = the smaller of 90% of this year's estimated tax, or 100% (110% if prior-year AGI exceeded $150,000) of last year's total tax liability.

Worked example

$100,000 expected net self-employment income, $20,000 prior-year tax, $90,000 prior-year AGI: SE tax of about $14,130, federal income tax of about $11,616, for a total estimated tax of about $25,745 — a quarterly payment of about $6,436. The safe-harbor annual payment (100% of last year's $20,000 tax) is about $5,000/quarter.

2026 quarterly estimated tax due dates

2026 quarterly estimated tax due dates
Period	Income earned	Due date
Q1	Jan 1 – Mar 31, 2026	April 15, 2026
Q2	Apr 1 – May 31, 2026	June 15, 2026
Q3	Jun 1 – Aug 31, 2026	September 15, 2026
Q4	Sep 1 – Dec 31, 2026	January 15, 2027

Interpreting your result

Models a single filer using the standard deduction, federal income tax, and federal SE tax only — no state estimated tax, itemized deductions, QBI deduction, or other filing statuses. Paying at least the safe-harbor amount each quarter avoids the IRS underpayment penalty even if actual liability is higher.

Recommendations

• The safe-harbor percentage jumps from 100% to 110% of last year's tax once your prior-year AGI exceeds $150,000.
• Quarterly periods are uneven by design (Q2 spans 2 months, Q3 spans 3) — this follows the IRS's own Form 1040-ES schedule.
• The January (Q4) payment can be skipped if you file your full tax return and pay any remaining balance by February 1.

Frequently asked questions

Paying at least the safe-harbor amount avoids an IRS underpayment penalty — even if your actual tax bill ends up higher, you'd just owe the difference at filing without a penalty.