OASDI vs Medicare Tax for Self-Employment (2026 Breakdown): Schedule SE, Wage Base, Additional Medicare

Self-employment tax is the single largest tax line item for most self-employed Americans — bigger than federal income tax for many filers earning under $80,000. The 15.3% combined rate (Social Security 12.4% + Medicare 2.9%) is the self-employed's equivalent of the FICA tax that W-2 employees split with their employer. Understanding exactly how OASDI (the Social Security side) and Medicare (the Medicare side) work — and how the Additional Medicare Tax kicks in above $200,000 — is essential for accurate quarterly estimated tax payments and year-end tax planning.

This guide breaks down the 2026 self-employment tax mechanics using the inflation-adjusted figures from the Social Security Administration's October 2025 announcement and IRS Rev. Proc. 2025-32, with worked examples for $50,000, $150,000, and $300,000 of self-employment income.

The Statutory Framework — How SE Tax Compares to FICA

FICA (Federal Insurance Contributions Act) under IRC Chapter 21 applies to W-2 wages. The W-2 employee pays 6.2% Social Security and 1.45% Medicare; the employer pays a matching 6.2% + 1.45% (with the 0.9% Additional Medicare withheld from employee wages only). Total: 7.65% employee + 7.65% employer = 15.3% combined.

SECA (Self-Employment Contributions Act) under IRC Chapter 2 imposes the same economic burden on the self-employed by requiring them to pay both sides — the full 15.3% — on their net earnings from self-employment. The "half-SE deduction" under IRC §164(f) allows the self-employed to deduct one-half of the SE tax in computing adjusted gross income, partially recreating the W-2 employer-side deduction.

The Three Components of 2026 SE Tax

OASDI (Old-Age, Survivors, and Disability Insurance) — 12.4%

Applied to net earnings from self-employment up to the 2026 Social Security wage base of $176,100 (Social Security Administration announcement October 2025). Earnings above the wage base are not subject to OASDI tax. Maximum 2026 OASDI tax: 12.4% × $176,100 = $21,836.40.

The wage base is indexed annually to average wage growth. Recent history:

For 2026, SSA announced no increase from 2025 because the underlying wage index calculation did not produce a meaningful change. Verify on ssa.gov for any mid-year revision.

Medicare — 2.9%

Applied to all net earnings from self-employment with no wage base cap. A self-employed individual with $1,000,000 of net SE earnings owes Medicare tax on all $1,000,000 (2.9% × $1,000,000 = $29,000). No exception or threshold.

Additional Medicare Tax — 0.9%

Per IRC §1401(b)(2), an additional 0.9% Medicare tax applies to combined wages + net earnings from self-employment above the following thresholds (NOT inflation-adjusted, fixed by statute):

Additional Medicare Tax is calculated on Form 8959 (Additional Medicare Tax) and reported on Schedule 2 of Form 1040. Unlike regular Medicare, the Additional Medicare Tax is NOT deductible as the half-SE deduction — only the base 2.9% portion qualifies.

The Half-SE Deduction Under IRC §164(f)

To recreate the W-2 employer-side tax deduction for the self-employed, IRC §164(f) allows the self-employed to deduct one-half of their total SE tax (excluding the Additional Medicare Tax) on Schedule 1 of Form 1040 as an above-the-line adjustment to income.

The deduction reduces:

• Adjusted Gross Income (and therefore federal income tax)
• State income tax (in states that conform to federal AGI)
• Other income-driven thresholds (Premium Tax Credit, Roth IRA contribution limits, Saver's Credit)

The deduction does NOT reduce:

• Self-employment tax itself (the SE tax base is unaffected)
• Net earnings from self-employment for retirement plan contribution limits (which uses a separate adjusted calculation)
• The Additional Medicare Tax (the 0.9% portion is excluded from the deduction)

Schedule SE — How the Calculation Works

The self-employed completes Schedule SE (Self-Employment Tax) attached to Form 1040. The 2026 Schedule SE (form likely renumbered Schedule 2 sub-line in 2026 — verify with IRS) follows this flow:

1. Net earnings from self-employment. From Schedule C net profit (sole proprietor), Schedule F (farm), Schedule K-1 partnership income (general partners; limited partners excluded for SE tax purposes per §1402(a)(13)).
2. SE-tax-adjusted net earnings. Multiply net SE earnings × 0.9235 (the "92.35% adjustment" — this corrects for the fact that the employer-side FICA is not subject to FICA itself in the W-2 context).
3. OASDI calculation. Apply 12.4% to the lesser of adjusted SE earnings or $176,100. Maximum: $21,836.
4. Medicare calculation. Apply 2.9% to all adjusted SE earnings. No cap.
5. Total SE tax. Sum of OASDI + Medicare.
6. Half-SE deduction. Multiply total SE tax × 0.5. Report on Schedule 1.
7. Additional Medicare Tax. Separate Form 8959 calculation. Combine W-2 wages + SE earnings, subtract filing-status threshold, multiply excess by 0.9%.

Worked Example #1 — $50,000 Self-Employment Income (Single Filer)

Worked Example #2 — $150,000 Self-Employment Income (MFJ)

Worked Example #3 — $300,000 Self-Employment Income (Single Filer)

Quarterly Estimated Tax Payments

Self-employed individuals generally must pay quarterly estimated taxes (Form 1040-ES) to avoid underpayment penalties under IRC §6654. The four quarterly deadlines for 2026 (with the typical first-business-day-after-weekend convention):

Safe harbor from the underpayment penalty: pay (a) 100% of prior-year total tax (110% if prior-year AGI exceeded $150,000), or (b) 90% of current-year tax. The IRS calculates the penalty on Form 2210 (Underpayment of Estimated Tax) — the penalty is computed as the federal short-term rate plus 3% applied to each quarter's underpayment for the period it was late.

The §1402(a)(13) Limited Partner Exception

One of the most consequential planning opportunities in SE tax is the §1402(a)(13) limited partner exception. K-1 income distributed to a "limited partner as such" is excluded from self-employment tax — meaning a passive LLC member or limited partner reports the K-1 income on Schedule E (no SE tax) rather than Schedule C (full SE tax).

The IRS has aggressively challenged the application of this exception in recent litigation (notably Renkemeyer, Campbell & Weaver LLP v. Commissioner, 136 T.C. 137 (2011); Castigliola v. Commissioner, T.C. Memo. 2017-62; Soroban Capital Partners LP v. Commissioner, 161 T.C. No. 12 (2023)). The current general rule: an LLC member who "actively participates" in the LLC's business does NOT qualify for the limited partner exception, even if state law calls them a limited partner. Active participation typically requires more than 500 hours per year of participation; passive participation under 100 hours per year likely qualifies. Consult a tax attorney for any structuring decision under §1402(a)(13).

S Corporation Strategy

For self-employed individuals netting above approximately $80,000-$100,000, electing S corporation status can substantially reduce SE tax. The mechanics:

• The self-employed forms an LLC and elects S corporation tax treatment via Form 2553.
• The owner pays themselves a "reasonable compensation" salary as a W-2 employee — subject to FICA (7.65% × 2 = 15.3%).
• The remaining business profit flows through as K-1 distribution — NOT subject to SE tax under §1402(a)(2) (which excludes corporate dividends from SE tax).

Example: Sara nets $200,000 from her consulting LLC in 2026. As a single-member LLC taxed as a disregarded entity, she would owe approximately $26,000 in SE tax. Electing S corporation status with a $120,000 reasonable salary + $80,000 K-1 distribution: FICA on $120,000 = $18,360; K-1 distribution = $0 SE tax. Total payroll tax burden ~$18,360 — saving ~$7,640/year vs sole proprietorship.

Important caveat: the "reasonable compensation" must be defensible based on industry comparables, hours worked, and job responsibilities. IRS routinely audits and recharacterizes underpaid S corp owner salaries — penalty exposure can be substantial. See our companion guide on SEP-IRA vs Solo 401(k) 2026 for related retirement-plan implications of the S corp strategy.

Net Investment Income Tax (NIIT) — Separate from SE Tax

The 3.8% Net Investment Income Tax under IRC §1411 applies to passive investment income (interest, dividends, capital gains, rental income, royalties) above the same $200,000/$250,000 thresholds. NIIT is NOT applied to self-employment income — the active business income is excluded. But NIIT may apply to interest/dividends from a self-employed individual's high-balance business cash account if the income is passive in character. Calculated on Form 8960 separately from Form 8959.

Frequently Asked Questions