Self-Employment Tax: How Schedule SE Actually Works
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Self-employment (SE) tax is the self-employed equivalent of FICA. For 2026, net SE earnings are multiplied by 92.35% to reach the SE-tax base; that base is taxed at 12.4% Social Security up to the $184,500 wage base and 2.9% Medicare with no cap, plus a 0.9% Additional Medicare surtax above $200,000 single / $250,000 MFJ. Half of SE tax is deducted above the line on Schedule 1.
The 92.35% multiplier
SE tax does not apply to gross self-employment income; it applies to 92.35% of net earnings from self-employment. The 7.65% reduction is the statutory employer-equivalent that an employer would pay in FICA on a wage of the same economic value (IRC §1402(a)(12)). Net earnings from SE = net Schedule C profit (and partnership Schedule K-1 box 14A, where applicable).
Social Security: 12.4% to the wage base
The 12.4% Social Security portion applies to the SE-tax base up to the 2026 wage base of $184,500 (SSA cost-of-living adjustment). W-2 wages and SE earnings stack: if W-2 wages were $150,000, only $34,500 of SE base is subject to the Social Security portion. Above the base, only the Medicare portion applies.
Medicare: 2.9% uncapped + 0.9% Additional Medicare
The 2.9% Medicare portion applies to the entire SE-tax base with no cap. The 0.9% Additional Medicare Tax (IRC §3101(b)(2) / §1401(b)(2)) applies to combined wages + SE earnings above $200,000 single / $250,000 MFJ / $125,000 MFS. Additional Medicare is reported and computed on Form 8959.
Half-SE above-the-line deduction
One-half of SE tax (the employer-equivalent portion) is deducted on Schedule 1 line 15. This reduces AGI — affecting QBI taxable-income tests, IRA contribution limits, ACA premium tax credit, and most phase-out thresholds. The deduction does not reduce SE tax itself; it reduces income tax only.
Quarterly planning
SE tax is owed quarterly via Form 1040-ES. Safe harbour is 100% of last year's total tax (110% if prior-year AGI > $150,000) or 90% of current-year tax. SE tax counts toward the safe-harbour figure — it is part of "total tax" for §6654 purposes.
Worked example: Devon Park, freelance copywriter (Brooklyn, NY)
Devon's 2026 Schedule C net profit is $120,000. No W-2 wages. Single filer.
SE-tax base: 120,000 × 0.9235 = 110,820 Social Security (12.4%): 110,820 × 0.124 = 13,742 (below the $184,500 wage base, so the full SS portion applies) Medicare (2.9%): 110,820 × 0.029 = 3,214 Additional Medicare (0.9% on SE base > $200k): n/a (under threshold) Total SE tax: 13,742 + 3,214 = 16,956 Half-SE deduction (Schedule 1 line 15): 16,956 / 2 = 8,478
Statute references
- Self-employment tax imposed —
IRC §1401 - Definition of net earnings from SE (92.35% multiplier) —
IRC §1402(a) - Half-SE deduction —
IRC §164(f) - Additional Medicare Tax —
IRC §1401(b)(2) / §3101(b)(2)
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