Tax Brackets for Small Business Owners: Marginal vs. Effective Rate
One of the most common misconceptions among small business owners is that “being in the 24% bracket” means paying 24% on all income. It doesn’t. The US tax system is progressive: the first dollars of taxable income are taxed at 10%, the next portion at 12%, the next at 22%, and so on. Only the dollars above each bracket threshold are taxed at the higher rate. The result is that the effective tax rate (total tax divided by total income) is always lower than the marginal rate (the rate on the last dollar earned). Understanding this distinction prevents two costly mistakes: over-estimating tax liability (and over-saving, reducing cash available for the business) and turning down additional income because of bracket fear.
2025 federal income tax brackets (single filer):
| Taxable Income | Rate |
|---|---|
| $0 - $11,925 | 10% |
| $11,926 - $48,475 | 12% |
| $48,476 - $103,350 | 22% |
| $103,351 - $197,300 | 24% |
| $197,301 - $250,525 | 32% |
| $250,526 - $626,350 | 35% |
| Over $626,350 | 37% |
“Taxable income” isn’t gross income or net profit. For a sole proprietor with $100,000 net profit:
- Net profit: $100,000
- Minus half of SE tax (deduction): $7,065
- Minus standard deduction: $15,750
- Minus QBI deduction (20% of net): $20,000
- Taxable income: $57,935
The owner is “in the 22% bracket” (taxable income falls between $48,476 and $103,350). But the effective income tax rate is much lower:
- First $11,925 at 10% = $1,193
- Next $36,550 at 12% = $4,386
- Next $9,460 at 22% = $2,081
- Total income tax: $7,660
- Effective income tax rate: $7,660 / $100,000 = 7.7%
Self-employment tax adds significantly:
- SE tax: $100,000 x 92.35% x 15.3% = $14,130
- SE tax effective rate: 14.1%
- Combined effective federal rate: 7.7% + 14.1% = 21.8%
The bracket fear mistake: A business owner earning $100,000 is offered a $20,000 project. They worry: “won’t that push me into the 24% bracket?” The answer: only the income above $103,350 (after deductions) is taxed at 24%. The additional $20,000 will be taxed at approximately 22% on income tax plus 15.3% on SE tax. The owner keeps approximately $12,500 of the $20,000 after federal taxes. Turning down the project to “stay in a lower bracket” makes no financial sense.
Self-employment tax phases out partially:
- The Social Security portion (12.4%) applies only to the first $176,100 of net SE earnings (2025)
- Above $176,100: only the Medicare portion (2.9%) applies, plus the 0.9% Additional Medicare Tax above $200,000 (single) / $250,000 (MFJ)
- This means the effective SE tax rate drops from 15.3% to 3.8% on income above $176,100
What’s the tax on each extra dollar of business income?
What strategies can reduce self-employment tax?
The most common approach is electing S-Corp status, which lets you split business income between a reasonable salary (subject to payroll tax) and distributions (not subject to FICA). Maximizing legitimate business deductions reduces net profit and therefore the base for self-employment tax. Contributing to a SEP-IRA or solo 401(k) reduces income tax but does not reduce self-employment tax because the contribution is calculated after SE tax. Hiring your children under age 18 (for a sole proprietorship or spousal partnership) shifts income to them without triggering FICA on their wages. Forming a limited partnership where you are a limited partner can avoid SE tax on partnership income, but the IRS scrutinizes this closely for service businesses.
How is the self-employment tax calculated?
Self-employment tax is 15.3% on net self-employment income up to the Social Security wage base ($168,600 in 2024), then 2.9% on income above that threshold. Net self-employment income is calculated as 92.35% of your Schedule C net profit (the 7.65% reduction approximates the employer-half FICA deduction that W-2 workers receive). You deduct half of the self-employment tax on Schedule 1 of Form 1040, which reduces your AGI and income tax but does not reduce the SE tax itself. The additional Medicare tax of 0.9% applies to combined wages and self-employment income exceeding $200,000 ($250,000 married filing jointly). This makes the effective rate on high-income self-employment earnings 16.2%.
Related guides:
How do you calculate the self-employment tax deduction?
The self-employment tax is 15.3% of net self-employment earnings (12.4% Social Security on income up to the wage base of $176,100 for 2025, plus 2.9% Medicare on all earnings). Before calculating the tax, you multiply net earnings by 92.35% (0.9235) to account for the fact that employees only pay tax on wages after the employer’s share is excluded. You deduct half of the self-employment tax as an above-the-line deduction on Form 1040, which reduces your AGI but not your self-employment income for SE tax calculation purposes. The additional 0.9% Medicare surtax applies to self-employment income exceeding $200,000 for single filers or $250,000 for joint filers, and this additional tax is not eligible for the 50% deduction.
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Yarik Yarosh, CPA. "Tax Brackets for Small Business Owners: Marginal vs. Effective Rate." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/small-business-tax-brackets-marginal-vs-effective
This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.