Self-employment tax is 15.3% on 92.35% of your net earnings — 12.4% for Social Security (up to the $184,500 wage base in 2026) plus 2.9% for Medicare on everything, with an extra 0.9% Medicare tax above $200,000 single / $250,000 joint. It's separate from income tax, it applies from the first $400 of net earnings, and yes — you can owe it even when you owe zero income tax.
Why this tax blindsides new freelancers
As an employee, you never really meet the full cost of Social Security and Medicare. You see 7.65% come out of your paycheck; your employer quietly pays the other 7.65% behind the curtain. When you go out on your own, the curtain lifts: you are now both the employee and the employer, so you pay both halves — the full 15.3%.
That alone would be manageable if people expected it. What makes it a shock is the timing. Employees pay tax with every paycheck, automatically. Freelancers get the whole check, spend like it's all theirs, and meet the tax bill once a year in April — when it's far too late to budget for it. The IRS knows this, which is why it runs a pay-as-you-go system: if you'll owe $1,000 or more, you're expected to send estimated payments four times a year, and there are penalties for skipping them.
The fix is mechanical, not mathematical: set the money aside the day each payment arrives. Open a separate savings account, move 25–30% of every invoice into it immediately, and pay your quarterly estimates from that account. The estimator above gives you a personalized percentage to replace the rule of thumb.
How the estimate is calculated
The calculator runs the same sequence the IRS uses, simplified for planning:
- Self-employment tax base: net earnings × 92.35%. The 7.65% haircut mirrors the employer-half treatment employees get. No SE tax at all if net earnings are under $400.
- Social Security: 12.4% on the base up to the 2026 wage base of $184,500. Earnings above that pay no additional Social Security tax.
- Medicare: 2.9% on the entire base, no cap — plus an additional 0.9% on base earnings above $200,000 (single) or $250,000 (married filing jointly).
- Federal income tax: adjusted gross income is approximated as net earnings minus half of SE tax (which is deductible). Subtract the 2026 standard deduction ($16,100 single / $32,200 joint), then apply the 2026 marginal brackets (10%, 12%, 22%, 24%, 32%, 35%, 37%).
- State tax: a planning estimate using 2026 published state rates on (net earnings − half of SE tax). States with no wage income tax show $0. For graduated-rate states the top marginal rate is applied, which makes the figure an upper bound — your real state tax is usually lower once brackets and deductions apply.
What's deliberately left out: the 20% qualified business income (QBI) deduction, tax credits, retirement plan contributions, itemized deductions, and local/city taxes. That means this estimate leans conservative — most freelancers' actual liability comes in somewhat lower, which is the safe direction for planning.
Worked example
Alex is a single freelance developer in Texas with $80,000 of net self-employment income for 2026:
- SE tax base: $80,000 × 92.35% = $73,880
- Social Security: $73,880 × 12.4% = $9,161.12 (under the wage base, so all of it counts)
- Medicare: $73,880 × 2.9% = $2,142.52
- Self-employment tax: $11,303.64
- AGI: $80,000 − $5,651.82 (half of SE tax) = $74,348.18
- Taxable income: $74,348.18 − $16,100 (standard deduction) = $58,248.18
- Federal tax: 10% × $12,400 ($1,240) + 12% × $38,000 ($4,560) + 22% × $7,848.18 ($1,726.60) = $7,526.60
- Texas state tax: $0 (no income tax)
- Total: $18,830.24 → $4,707.56 per quarter, an effective rate of about 23.5%.
Notice the structure: SE tax ($11,304) is the bigger half of the bill. That's the piece new freelancers forget — and exactly why the rule of thumb starts at 25%, not 15%.
Quarterly payments, without the dread
The quarterly system sounds bureaucratic but it's just four deadlines: mid-April, mid-June, mid-September, and mid-January. Each payment should be about a quarter of what you'll owe for the year. The IRS offers a safe harbor — pay at least 100% of last year's total tax (110% at higher incomes) across the four quarters and you generally avoid underpayment penalties even if this year's income surprises you.
Practically speaking: take the quarterly figure from the calculator, set up the payments, and stop thinking about taxes until next quarter. The freelancers who get in trouble aren't the ones who estimate imperfectly — they're the ones who never set up the system at all.