Qualified business income deduction (IRC 199A) is 20% of QBI, capped at 20% of taxable income. It shrinks the income you later apply income-tax brackets to. It is not a 20% off coupon on your whole bill. It does not reduce self-employment tax.
Live engine, same numbers as the calculator page:
- QBI $100,000, taxable income $80,000
- 20% of QBI = $20,000
- 20% of TI = $16,000
- Deduction = $16,000 (the TI cap)
Run the QBI §199A calculator →
SECA on $80,000 net earnings is $11,303.64 (taxable base $73,880). Self-employment tax. Hub: United States calculators.
This engine does not model SSTB phase-outs, W-2 wage or UBIA limits, or the net-capital-gain haircut. High earners can get less than 20%. Estimate, not a filed 1040. There is no live Form 1040 tax engine on this page.
Direct answer: $16,000 off taxable income
- 0.20 × $100,000 = $20,000
- 0.20 × $80,000 = $16,000
- Deduction = min($20,000, $16,000) = $16,000
- That $16,000 is 20% of taxable income, not 20% of the tax itself
- SE tax on $80,000 net still uses 92.35% × 15.3% on the SECA base = $11,303.64
deduction = min(0.20 × QBI, 0.20 × taxable income)
People quote “20% effective rate” after they see 199A. Wrong object. 20% is the deduction. Your effective income-tax rate is tax ÷ income after that deduction (and after the standard deduction, credits, and the rest). Your effective SECA rate is still about 14.13% of net ($11,303.64 ÷ $80,000) until the Social Security wage base bites.
Checks you can re-run
| QBI | Taxable income | 20% QBI | 20% TI | Deduction |
|---|---|---|---|---|
| $50,000 | $200,000 | $10,000 | $40,000 | $10,000 |
| $80,000 | $80,000 | $16,000 | $16,000 | $16,000 |
| $80,000 | $60,000 | $16,000 | $12,000 | $12,000 |
| $100,000 | $80,000 | $20,000 | $16,000 | $16,000 |
SECA on $80,000: 0.9235 × $80,000 = $73,880. Social Security 12.4% = $9,161.12. Medicare 2.9% = $2,142.52. Total $11,303.64. Topic 554. The $50,000 golden case on that page is $7,064.78.
What QBI does not do
- Does not cut the backup withholding 24% line.
- Does not replace estimated-tax safe harbor.
- Does not turn a 1099 into a W-2. SE take-home vs W-2.
No. You have $16,000 less taxable income. A 22% last-dollar band would save about $3,520 of income tax on that slice, not $16,000. We do not run a full 1040 here.
No. SECA is IRC 1401 on 92.35% of net earnings. QBI is an income-tax deduction.
Because taxable income is $80,000. The cap is 20% of that.