The two components of SE tax
| Component | Rate | Applies to (2025) |
|---|---|---|
| Social Security | 12.4% | First $176,100 of net earnings |
| Medicare | 2.9% | All net earnings (no cap) |
| Additional Medicare | +0.9% | Earnings above $200k single / $250k MFJ |
Total for most self-employed people: 15.3% on the first $176,100 of net earnings, then 2.9% above that.
The 92.35% adjustment
SE tax doesn't apply to 100% of your net earnings. It applies to 92.35% of them. Why? Because the IRS simulates the fact that a W-2 employee's wages don't include the employer's share of FICA.
So the real formula is:
Net SE earnings × 0.9235 × 15.3% = SE tax owed.
The deduction for the "employer half"
You get to deduct half of your SE tax (the "employer half") on Schedule 1, Line 15. This reduces your AGI and therefore your income tax — but not your SE tax itself.
Example: $10,000 SE tax owed. You deduct $5,000 on Schedule 1. At a 22% bracket, that saves $1,100 in income tax.
Worked example: $80,000 net SE earnings
- Taxable for SE purposes: $80,000 × 0.9235 = $73,880
- SE tax: $73,880 × 15.3% = $11,304
- Employer-half deduction: $11,304 ÷ 2 = $5,652 (goes on Schedule 1 Line 15)
- If you're in the 22% bracket, the deduction saves: $5,652 × 22% = $1,243 in income tax
- Net cost of SE tax after deduction: $11,304 − $1,243 = $10,061 effectively
When do you owe SE tax?
You owe SE tax if your net earnings from self-employment were $400 or more. The filing threshold is much lower than for income tax. Even if you don't owe income tax, you may owe SE tax.
How it's paid
- If you expect to owe $1,000+ in total tax, you must pay quarterly estimated tax (Form 1040-ES). Safe harbor rule here.
- Otherwise, it's due with your annual return by April 15.
- If you have a W-2 job plus self-employment, you can increase W-2 withholding instead of making quarterlies.
Where SE tax sits on your return
The calculation lives on Schedule SE. The result flows to:
- Schedule 2, Line 4 — the tax owed
- Schedule 1, Line 15 — the half-deduction
Both flow into Form 1040 in the usual spots.
Why S-Corp election reduces SE tax
This is the main appeal of the S-Corp election for profitable self-employed people. An S-Corp owner pays themselves a "reasonable salary" (subject to SE tax equivalent via W-2 FICA) plus takes the remainder as a distribution (not subject to SE tax).
Example: $150,000 net profit.
- As Schedule C: SE tax on 92.35% × 15.3% ≈ $21,200 (up to the SS cap, then 2.9%)
- As S-Corp with $80k "reasonable salary": FICA on $80k ≈ $12,240. Remaining $70k as distribution: $0 SE/FICA.
- Savings: ~$9,000/year
S-Corp has real costs (payroll, additional tax return, state fees), so it's not free. When S-Corp pays off.
Common SE tax mistakes
- Forgetting the employer-half deduction — software usually does this, paper filers often miss it
- Doubling up if you have W-2 income — if your W-2 wages already hit the SS cap ($176,100), your SE earnings only pay Medicare, not the full 15.3%
- Not paying quarterly — underpayment penalty is currently around 8% annually
- Thinking the SE tax deduction reduces SE tax — it reduces income tax, not SE tax itself
We verify your SE tax calculations.
Including the employer-half deduction, the SS cap interaction, and whether S-Corp would save you money.