SECA vs FICA comes down to one structural difference: both collect the same 15.3% in Social Security and Medicare taxes, but FICA splits the bill between employer and employee, while SECA makes self-employed workers pay the whole amount themselves. Every other distinction, from how taxable income is calculated to when payments are due, flows from that split.
Who Pays What
The rates are identical under both systems. Social Security (Old-Age, Survivors, and Disability Insurance) is taxed at 12.4%, and Medicare (Hospital Insurance) is taxed at 2.9%, for a combined 15.3%. Those numbers have been fixed since 1990. Under FICA, they appear in IRC §§ 3101 and 3111; under SECA, in IRC § 1401.
Under FICA, you and your employer each pay 7.65% (6.2% for Social Security plus 1.45% for Medicare). Your employer withholds your share from each paycheck and sends the combined 15.3% to the IRS. Under SECA, you owe the full 15.3% yourself, because there is no employer to cover the other half.
How the Taxable Amount Is Figured
FICA applies to gross wages, salaries, tips, and bonuses. Most cash compensation counts, though certain employer-provided fringe benefits (employer-sponsored health insurance, limited educational assistance, HSA contributions, and qualified commuter benefits, among others) are excluded before the tax is calculated.
SECA works differently. You don’t pay on gross receipts. You start with net earnings, which is gross income minus ordinary business expenses (the figure that comes off Schedule C for sole proprietors). You then multiply that net profit by 92.35%. The multiplier exists to put you on roughly equal footing with employees by removing the portion of your earnings that corresponds to the employer’s share of FICA, which employees never pay tax on either. The result is your self-employment income for tax purposes.
SECA also has a floor that FICA doesn’t. You owe self-employment tax only if your net earnings from self-employment reach $400 or more in a tax year. Below that, you don’t file Schedule SE and owe nothing. It’s a hard cutoff: $399 in net earnings means zero SECA tax.
The Social Security Wage Base
The 12.4% Social Security portion only applies up to an annual earnings cap that adjusts for inflation. For 2026, the cap is $184,500. Every dollar above that is exempt from the Social Security piece, though the 2.9% Medicare tax keeps going with no ceiling.
The cap works the same under both systems. An employee earning $200,000 in W-2 wages has employer withholding of the 6.2% Social Security portion stop once year-to-date wages hit $184,500. A self-employed worker with $200,000 in net earnings (after the 92.35% adjustment) stops owing the 12.4% at the same point.
When You Have Both W-2 Wages and Self-Employment Income
If you hold a day job and run a side business, your W-2 wages count first toward the $184,500 Social Security cap. Only the remaining gap, if any, gets hit with the 12.4% portion of SECA. If your W-2 wages already meet or exceed the cap, you owe zero Social Security tax on your self-employment income. The 2.9% Medicare tax still applies to all of your net self-employment earnings regardless.
This is where miscalculations most often occur. Ignore your W-2 wages when figuring quarterly SECA estimates and you can overpay Social Security tax all year, then wait for a refund at filing.
The Additional Medicare Tax
An extra 0.9% Additional Medicare Tax kicks in once earnings cross a threshold tied to filing status:
- Single or head of household: $200,000
- Married filing jointly: $250,000
- Married filing separately: $125,000
The thresholds apply to both FICA wages and SECA income. For employees, the employer must start withholding the extra 0.9% once wages exceed $200,000 in a calendar year regardless of filing status, and any adjustment based on actual filing status is sorted out on the tax return. For self-employed workers, the Additional Medicare Tax is calculated on Schedule SE and paid with the return or through estimated payments. There is no employer match on the 0.9% under either system.
The 50% Deduction That Offsets SECA
Because self-employed workers pay both halves of the 15.3%, IRC § 164(f) lets you deduct half of your self-employment tax as an above-the-line adjustment on Form 1040. The deduction reduces adjusted gross income whether or not you itemize, which can lower your income tax bracket and affect eligibility for other deductions and credits.
One catch trips people up: the 50% deduction does not include the 0.9% Additional Medicare Tax. The statute explicitly excludes the tax imposed under § 1401(b)(2). If you owe the Additional Medicare Tax, that portion comes out of your pocket with no corresponding deduction. That mirrors the FICA side, where employers don’t match the 0.9% either.
How and When You Pay
Employers Under FICA
Employers report FICA taxes quarterly on Form 941. The deadlines fall on the last day of the month following each quarter: April 30, July 31, October 31, and January 31. Deposit on time all quarter and you get an extra 10 calendar days to file the return.
Self-Employed Workers Under SECA
Self-employed individuals report SECA tax on Schedule SE, filed with the annual Form 1040. Net business income typically flows from Schedule C onto Schedule SE, which handles the 92.35% adjustment, applies the rates, and produces the total. The 50% deduction then transfers to the front of Form 1040.
But you don’t wait until April to pay. The IRS requires quarterly estimated payments covering both income tax and self-employment tax. The four deadlines for 2026:
- January 1 – March 31 earnings: April 15
- April 1 – May 31 earnings: June 15
- June 1 – August 31 earnings: September 15
- September 1 – December 31 earnings: January 15, 2027
If a deadline lands on a weekend or federal holiday, the payment is due the next business day. To avoid an underpayment penalty, total payments for 2026 generally must equal the lesser of 90% of your 2026 tax liability or 100% of what you owed for 2025. If your 2025 adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the 100% figure rises to 110%.
Penalties
Employers who miss FICA deposit deadlines face escalating penalties based on how late the payment is:
- 1–5 days late: 2% of the unpaid deposit
- 6–15 days late: 5%
- More than 15 days late: 10%
- After IRS notice demanding payment: 15%
The percentages don’t stack. A deposit 10 days late triggers the 5% rate, not 2% plus 5%.
Self-employed workers who underpay estimated taxes face a penalty calculated as interest on the shortfall for each quarter. The IRS underpayment rate for the first quarter of 2026 is 7%, and it has held at that level through recent quarters. The penalty applies separately to each quarter’s underpayment, running from the due date until the tax is paid or until the annual return filing deadline, whichever comes first.
Statutory Employees: The Hybrid Category
A small group of workers, called statutory employees, are technically independent but treated as employees for Social Security and Medicare, meaning their clients withhold FICA rather than leaving them to pay SECA. The IRS recognizes four categories: certain delivery drivers, full-time life insurance agents working primarily for one company, home workers producing goods to an employer’s specifications, and full-time traveling salespeople turning in orders on behalf of a single firm. If you fall into one of these categories, Box 13 on your W-2 is checked, you report business expenses on Schedule C, and you do not file Schedule SE or pay self-employment tax.
For everyone else, the rate is the same either way. The real adjustment moving from employment to self-employment is cash-flow discipline: paying the full 15.3% yourself in quarterly installments instead of watching 7.65% quietly disappear from each paycheck.