By Harry Prabandham · Updated September 28, 2026
Tax Planning
Self-Employment Tax: How It's Calculated and What Actually Lowers It
Self-employment tax is 15.3% Social Security and Medicare on 92.35% of net self-employment earnings; in 2026 the 12.4% part stops at $184,500.
Self-Employment Tax: How It's Calculated and What Actually Lowers It
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What is self-employment tax?
- It is Social Security and Medicare tax for people who work for themselves: 12.4% for Social Security plus 2.9% for Medicare, 15.3% in total.
- Employees split these taxes with their employer; self-employed people pay both halves.
- It is owed in addition to income tax, generally when net self-employment earnings reach $400 or more for the year.
- Sole proprietors, independent contractors, and most general partners and LLC members active in the business are subject to it.
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Full Guide
What is self-employment tax?
- It is Social Security and Medicare tax for people who work for themselves: 12.4% for Social Security plus 2.9% for Medicare, 15.3% in total.
- Employees split these taxes with their employer; self-employed people pay both halves.
- It is owed in addition to income tax, generally when net self-employment earnings reach $400 or more for the year.
- Sole proprietors, independent contractors, and most general partners and LLC members active in the business are subject to it.
How is self-employment tax calculated?
- Start with net profit from Schedule C or your partnership K-1, then multiply by 92.35% to get net earnings from self-employment.
- The 12.4% Social Security portion applies only up to the 2026 wage base of $184,500, reduced by any W-2 wages you also earned.
- The 2.9% Medicare portion applies to all net earnings, with no cap.
- Half of the tax is deductible on Schedule 1, which lowers income tax but not the self-employment tax itself.
When does the Additional Medicare Tax apply?
- An extra 0.9% applies to combined wages and self-employment earnings above $200,000 single, $250,000 joint, or $125,000 married filing separately.
- There is no employer match on this portion, so it is paid entirely by the individual.
- These thresholds are set in the statute and are not indexed, so more earners reach them over time.
- It is separate from the 3.8% net investment income tax, which applies to investment income rather than earnings.
How do estimated payments work?
- Self-employed people generally pay tax through quarterly estimates on Form 1040-ES, due in April, June, September, and the following January.
- Payments should cover both income tax and self-employment tax.
- You generally avoid an underpayment penalty by paying 90% of this year's tax or 100% of last year's, or 110% if last year's AGI exceeded $150,000.
- If you also have a W-2 job, extra withholding there can cover some or all of what estimates would.
What actually lowers self-employment tax?
- Legitimate business expenses reduce net profit, which directly reduces self-employment tax.
- An S corporation election can limit payroll tax to a reasonable salary, but adds payroll, filing, and state costs.
- SEP-IRA or solo 401(k) contributions, HSA contributions, and self-employed health insurance lower income tax but do not reduce self-employment tax.
- Earnings above the Social Security wage base face only Medicare tax, which changes the math for higher earners.
What mistakes come up most often?
- Budgeting only for income tax and being surprised by the self-employment tax bill.
- Skipping estimated payments in the first profitable year and owing penalties and interest.
- Setting an S corporation salary unreasonably low, which invites IRS reclassification of distributions as wages.
- Forgetting that Schedule SE is still required when a W-2 job already covers the Social Security wage base.
Key takeaways
- Self-employment tax is 15.3% on 92.35% of net earnings, with the 12.4% part capped at $184,500 in 2026.
- An extra 0.9% Medicare tax applies above unindexed thresholds.
- Retirement and HSA contributions cut income tax, not self-employment tax.
- Entity choice and estimated payments are CPA decisions; Rubric coordinates with your CPA rather than preparing returns.
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