Compute Schedule SE self-employment tax, federal income tax estimate, QBI deduction, and your quarterly payment.
Total estimated tax (SE + federal income)
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SE tax (Schedule SE)
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Federal income tax
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Half-SE deduction
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Above-the-line, reduces federal AGI.
QBI deduction estimate
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Worked example
Take a single freelancer with $80,000 of net self-employment income, no W-2 wages, and QBI eligibility. Self-employment tax applies to 92.35% of net earnings, so the base is $73,880. The Social Security portion is 12.4% of that, $9,161.12, since the total is under the $176,100 wage base, and the Medicare portion is 2.9%, $2,142.52, for a total SE tax of $11,303.64. You deduct half of that, $5,651.82, above the line. The Qualified Business Income deduction is roughly 20% of business income after the half-SE deduction, about $14,869.64 here. Federal taxable income then becomes $80,000 minus the half-SE deduction, minus the QBI deduction, minus the $15,750 standard deduction, around $43,729, which produces about $5,009 of income tax. Adding SE tax and income tax gives a total estimated federal bill of $16,312.57, roughly $4,078 per quarter, an effective rate of about 20.4% on the $80,000.
| Step | Amount |
|---|---|
| Net SE income | $80,000 |
| SE earnings base (92.35%) | $73,880 |
| SE tax (12.4% SS + 2.9% Medicare) | $11,304 |
| Deductible half of SE tax | $5,652 |
| QBI deduction estimate | $14,870 |
| Federal income tax | $5,009 |
| Total estimated tax | $16,313 |
How it is calculated
Because the self-employed pay both the employee and employer halves of FICA, the combined rate is 15.3%, 12.4% for Social Security plus 2.9% for Medicare. That rate applies to 92.35% of net earnings, an adjustment that approximates the employer-side deduction a W-2 worker never sees. Social Security is capped at the $176,100 wage base, and any W-2 wages you also earn use up that cap first. You may deduct half of the SE tax when computing income tax, and many businesses also claim the 20% Qualified Business Income deduction. The tool then runs the federal brackets on income net of those deductions and the standard deduction, adds the full SE tax back on, and divides by four to estimate quarterly payments. High earners may also owe the 0.9% additional Medicare tax above the filing-status threshold.