Self-Employment Tax in Connecticut: The Federal Layer
Self-employed workers in Connecticut — freelancers, independent contractors, sole proprietors, single-member LLC owners — owe federal self-employment (SE) tax in addition to regular income tax. SE tax is 15.3% of 92.35% of net self-employment earnings: 12.4% for Social Security (capped at the wage base of $176,100 in 2026) plus 2.9% for Medicare (no cap, plus 0.9% surcharge on combined earnings above $200,000 single / $250,000 joint).
The "92.35% of net earnings" calculation effectively gives you a deduction for the employer-equivalent half of SE tax. You then deduct half of your SE tax (the "employer half") above-the-line on your Form 1040, reducing your federal taxable income. This deduction does not reduce SE tax itself — it only lowers the income tax base.
Connecticut State Income Tax on Self-Employment Income
Connecticut taxes self-employment income through the same progressive bracket structure that applies to wage income, with a top marginal rate of 6.99%. Unlike federal SE tax, Connecticut's state tax does not include a separate Social Security/Medicare component — those are federal only. State income tax is calculated on net SE income (after business expenses) plus other taxable income.
For a $75,000 net self-employment income in Connecticut, expect roughly $10,598 in federal SE tax (15.3% × 92.35%), federal income tax in the ~12%–22% bracket range depending on filing status, and Connecticut state tax of roughly $3,408–$4,456. Total all-in rate often runs 32.2%–39.2% on net SE earnings — substantially higher than W-2 employees because the self-employed pay both halves of FICA.
Quarterly Estimated Tax Payments — Required for Most Connecticut Self-Employed
If you expect to owe $1,000 or more in federal taxes after subtracting withholding and credits, the IRS requires quarterly estimated payments via Form 1040-ES. Payments are due April 15, June 15, September 15, and January 15 of the following year. Underpayment triggers a penalty calculated as interest on the shortfall. The safe harbor: pay at least 100% of last year's total tax (110% if AGI > $150,000) or 90% of current-year liability, spread evenly across the four quarters.
Connecticut typically requires quarterly state estimates as well; check your Connecticut Department of Revenue for the specific form (often a state-equivalent of 1040-ES) and threshold. Most accounting software calculates and reminds you of estimated payments automatically once you log net SE income.
Deductions That Reduce Connecticut Self-Employment Tax Burden
Business expenses reduce your net SE earnings, which reduces both federal SE tax (15.3%) and federal/state income tax. Common deductions: home office (simplified method allows $5/sq ft up to 300 sq ft), business mileage (federal rate updates annually, currently around $0.67/mile), health insurance premiums (above-the-line for self-employed, no AGI floor), business meals (50% deductible), professional development, software subscriptions, and equipment (Section 179 expensing or bonus depreciation).
Solo 401(k) and SEP-IRA contributions are powerful: a Solo 401(k) lets you contribute up to $24,500 as employee (2026) plus 25% of net SE earnings as employer, with combined limit of $70,000. SEP-IRA caps at 25% of net SE earnings up to $70,000. Both reduce federal taxable income and Connecticut state taxable income. For a freelancer netting $100,000, maxing a Solo 401(k) can shelter $40,000+ from current-year tax — a roughly $10,000–$15,000 deferral depending on bracket.