Self-employment tax is the Social Security and Medicare tax that people who work for themselves generally pay on net earnings from self-employment. On a W-2 job, FICA is split: your employer withholds the employee share and pays an employer share. When you are self-employed (Schedule C freelancers, many sole proprietors, and some partners), Schedule SE figures a tax that roughly covers both shares.
Form differences and mixed W-2/1099 years: W-2 vs 1099 tax basics. Cash-flow reserves: Side hustle quarterly taxes and Side hustle money basics.
What “net earnings” means here
Self-employment tax is not calculated on every dollar that hits Stripe, Square, Uber, or your business checking account. Broadly:
- Start with business profit on Schedule C (revenue minus ordinary and necessary expenses).
- Apply the Schedule SE definition of net earnings from self-employment (a percentage factor appears on the form - use the current IRS Schedule SE).
- Pay SE tax on that base up to the Social Security wage base for the OASDI portion; Medicare generally continues above that base (Additional Medicare Tax can apply at higher incomes).
Income tax on profit is separate. You can owe income tax and self-employment tax on the same net profit. Filing workflow: Filing taxes for beginners.
Eligible pass-through profit may also support a Section 199A deduction on the income-tax side: QBI deduction basics.
The deduction for “one-half” of SE tax
You may deduct one-half of your self-employment tax when computing adjusted gross income (an above-the-line deduction on Form 1040). That deduction does not mean you only write a check for half. Cash still leaves for the full SE tax; the deduction only reduces the income-tax side of the return.
Software usually loops this correctly. Manual filers should follow Schedule SE and the Form 1040 instructions for the year.
Worked example: illustrative rates only
Casey has $40,000 Schedule C profit after expenses in a sample year (no employees). Using simplified educational math (confirm current Schedule SE factors and wage base):
| Step | Illustrative figure |
|---|---|
| Approximate SE tax base | ~92.35% × $40,000 ≈ $36,940 |
| Combined SE rate often cited | 15.3% (12.4% Social Security + 2.9% Medicare) on the base, subject to wage-base caps |
| Rough SE tax | ≈ $5,650 |
| Deductible half (AGI) | ≈ $2,825 |
| Still remitted | Full SE tax via estimates / return |
Casey also owes income tax on profit after that half-SE deduction and other adjustments. Parking roughly 25–30% of profit for federal tax (plus state if any) is a common reserve habit until a real projection exists - not a universal rule.
How this ties to quarterly estimates
Because platforms rarely withhold SE tax, many self-employed people pay through Form 1040-ES quarterly estimates or by raising W-2 withholding on a day job. Workflow: How to estimate quarterly estimated taxes. When income is rising, prior-year safe-harbor percentages can prevent underpayment penalties: Estimated tax safe harbor rules.
Pay via IRS Direct Pay or EFTPS; keep confirmation numbers next to bookkeeping in QuickBooks, Wave, or a spreadsheet.
Common mix-ups
- Treating gross deposits as the SE tax base (expenses matter).
- Forgetting that LLC single-member defaults are still often Schedule C / SE unless taxed as an S corp (S corp payroll is a different design - get professional help before DIY payroll).
- Assuming a 1099-NEC under a threshold means “no SE tax” - filing thresholds for forms and taxability of net earnings are not the same question.
- Ignoring state income tax estimates when your state requires them (State tax basics).
Named payroll/tax contexts people bump into: IRS Schedule SE, SSA wage-base notices, and preparer software from TurboTax, H&R Block, or a CPA firm.
High-limit retirement sheltering on net profit often starts with a SEP IRA for side income or a solo 401(k). Shops with employees may evaluate a SIMPLE IRA instead.
Checklist
- Track revenue and expenses so Schedule C profit is real, not vibes.
- Project SE tax + income tax; automate a reserve transfer.
- Calendar quarterly estimates or adjust W-2 withholding.
- Complete Schedule SE at filing; claim the allowable half-SE deduction.
- Watch the Social Security wage base if you also have W-2 wages (combined caps).
- Re-forecast after a big client lands or disappears.
Classic residential rental losses on Schedule E follow passive activity rules more than self-employment tax: Passive activity loss basics.
Self-employed Americans abroad still work through Schedule SE alongside any Form 2555 exclusion: FEIE basics.
Above-the-line self-employed health insurance premiums (does not cut SE tax): SE health insurance deduction.
Educational only. Not tax advice. Rates, wage bases, Additional Medicare Tax thresholds, and Schedule SE lines change; confirm with current IRS instructions and a credentialed preparer (CPA, EA, or tax attorney).