Self-employment tax calculator

Self-employment tax is not an extra tax — it is the half your employer used to pay

Every employee in the country pays 7.65% of their wages into Social Security and Medicare, and their employer pays the same amount again on top. The employee never sees the second half; it does not appear on the payslip and most people have no idea it exists.

When you work for yourself there is no employer, so you pay both halves. That is self-employment tax: 12.40% for Social Security and 2.90% for Medicare, 15.30% in total. It is not a penalty for being self-employed and it buys the same benefits — it is simply the whole cost, visible for the first time.

Two adjustments soften it and both are easy to miss. Only 92.35% of your net profit is subject to it (§ 1402(a)(12)), and you deduct half of what you pay from your adjusted gross income (§ 164(f)). On $80,000 of profit that is $11,304 of self-employment tax and a $5,652 deduction against income tax.

The number that actually matters is the comparison. $80,000 of self-employment profit costs $16,647 in total federal tax; the same $80,000 as a salary costs $14,890. The gap of $1,757 is the employer half you are now covering yourself, and it is the single most important number in any decision about invoicing rather than being on a payroll.

Which is why a contract rate has to exceed the salary it replaces by more than people assume. Matching $80,000 of take-home from a salary needs roughly $81,757 of profit before you have accounted for health cover, paid leave, or an employer retirement match — none of which arrive with an invoice.

The number to enter is profit, not what you invoiced

Self-employment tax applies to net profit: what you billed, minus the ordinary and necessary costs of earning it. Someone who invoiced $120,000 and spent $40,000 running the business pays on $80,000, not on $120,000.

The deductions people actually miss are rarely exotic. The qualified portion of a home office. Mileage for business driving, which at standard rates is usually worth more than tracking actual costs. Professional insurance and licensing. Software and subscriptions used for the work. Accountancy fees. A phone and internet line apportioned to business use. Equipment, which can often be expensed in the year of purchase rather than depreciated.

Two more that are commonly overlooked because they sit on the personal side of the return rather than on Schedule C: health insurance premiums for the self-employed, deductible above the line, and contributions to a SEP-IRA or solo 401(k), which for someone self-employed can shelter far more than an employee's contribution limit allows.

The discipline that makes all of this survivable is a separate bank account from the first day. Not for tax reasons — the law does not require it — but because reconstructing which of four hundred mixed transactions were business is the reason people either overpay or take positions they cannot document.

And note what is not deductible, because optimism here is expensive: commuting to a regular place of work, clothing that is wearable outside the job, the cost of meals eaten alone while working, and the portion of a mixed trip that was personal. A deduction that fails on audit costs the tax, the interest and the penalty.

The 20% deduction most self-employed people qualify for

Section 199A lets many self-employed people deduct up to 20% of qualified business income before income tax is computed. It is the largest single break available to someone working for themselves, it requires no spending, and a surprising number of people never claim it.

On $80,000 of profit, the deduction here is $11,650 — which at this income is limited not by the 20% of profit but by the 20%-of-taxable-income ceiling, the constraint that actually binds at ordinary incomes. It reduces the income tax bill, never the self-employment tax, which is charged before any of this.

Above $201,750 single or $403,500 joint the rules change, and this is where the profession matters. A "specified service trade or business" — law, medicine, accounting, consulting, financial services, performing arts, athletics — loses the deduction across a phase-in range ending at $276,750 single. A trade, a shop, a manufacturer or most freelancers outside those fields keeps it, subject instead to limits based on wages paid and property held.

The threshold is on taxable income, not on profit, which gives people more control over it than they expect. A retirement contribution that drops taxable income back below the line can restore a deduction worth several times the tax saving on the contribution itself — one of the few places in the code where two reliefs compound rather than compete.

The trap to avoid: assuming the deduction is automatic because it usually applies. It is claimed on the return, it interacts with the standard deduction in ways that change the arithmetic, and where a business shows a loss the negative amount carries forward against next year's qualified income.

Nobody is withholding anything, so you pay four times a year

An employee's tax arrives at the IRS in instalments all year without them doing anything. Self-employed income has no such mechanism, so the law requires estimated payments — 15 April, 15 June, 15 September, and 15 January of the following year, dates that are not evenly spaced and catch people out every June.

On $80,000 of profit the annual liability is $16,647, which is $4,162 a quarter if you simply divide. The safe harbour usually lets you pay less: $14,150 across the year in this example, because it is the lower of 90% of this year's tax and 100% of last year's — rising to 110.00000000000001% where the prior year's AGI exceeded $150,000.

Inside the safe harbour, owing money in April carries no penalty. Outside it, the underpayment penalty is computed quarter by quarter, which is what catches people who have a good year and try to fix it with one large payment in December. The first quarter needed paying in the first quarter, and a late catch-up does not undo it.

There is one asymmetry worth exploiting. Withholding is treated as paid evenly across the year no matter when it actually happened, while estimated payments are credited when made. So a household with one salary and one self-employed income can fix an underpayment discovered in November by increasing the W-4 withholding on the salary — and the whole amount counts as though it had been paid since January.

The practical system that works: a separate account, and a fixed percentage of every payment received moved into it the day it arrives. At this profit level roughly 20.81% covers federal; add your state's rate on top. Nobody has ever been penalised for having set aside too much.

When an S-corp starts to make sense, and when it does not

The most repeated advice in this area is to form an S-corp and save on payroll tax. The mechanism is real: an S-corp owner pays themselves a salary subject to FICA and takes the remaining profit as a distribution, which is not. On the distribution, the 15.30% simply does not apply.

The constraint is that the salary must be reasonable for the work actually performed. That is a facts-and-circumstances test rather than a formula, and setting it artificially low is the single most litigated issue in this corner of the code. Where it fails, distributions are recharacterised as wages with tax, interest and penalties, which costs more than the election ever saved.

Against the saving sit real costs: a payroll service, a separate corporate return, in several states a franchise tax or annual fee, and the administrative discipline of actually running payroll on a schedule. Those typically run $1,000 to $2,500 a year before anyone has saved anything.

The arithmetic therefore only works once profit meaningfully exceeds a defensible salary. At $80,000 of profit, where a reasonable salary might be most of it, there is little distribution left to shelter and the costs eat the benefit. At two or three times that, with a salary that still stands up, the numbers change substantially.

And an S-corp is not the only structure with consequences. A single-member LLC is disregarded for federal tax by default — it changes your liability exposure, not your tax bill, which is worth knowing before paying for one on the promise of tax savings it does not by itself provide.

The retirement accounts an employee cannot use

This is the compensation for paying both halves of FICA, and it is genuinely large. A solo 401(k) lets you contribute both as the employee and as the employer, so the combined limit is far above what a salaried worker can reach — and the employer portion is a percentage of business profit rather than a flat cap.

A SEP-IRA is the simpler alternative: a percentage of net self-employment earnings, no separate filing until the balance is substantial, and it can be opened and funded after year end, which makes it the tool for someone who discovers in March that last year was better than expected.

Every dollar contributed reduces income tax at your marginal rate and, in the right circumstances, does something more valuable: pulls taxable income back below the QBI threshold. Where that happens, the effective saving on the contribution exceeds the marginal rate by a wide margin, because it restores a deduction as well as sheltering income.

What none of them reduce is self-employment tax. That is charged on net profit before any retirement contribution, which is the same asymmetry an employee meets with a 401(k) and FICA. There is no structure that avoids it on genuine self-employment earnings, and any advice claiming otherwise is describing something else.

The health insurance deduction runs alongside and is often larger than people expect: premiums for yourself, a spouse and dependants, deductible above the line rather than as an itemised medical expense, limited to the profit of the business. For someone buying cover on an exchange, it is frequently the biggest single deduction on the return after the QBI.

The first year is the one that goes wrong

Almost every unaffordable April in this category is a first year. The pattern is consistent: income arrives all year with nothing withheld, it feels like the whole amount is yours because nothing was ever deducted from it, and the bill for the entire year lands at once when the money has already been spent.

The size is the shock. On $80,000 of profit that is $16,647 of federal tax — $11,304 of it self-employment tax alone — plus whatever your state takes, which on the same figure ranges from nothing to $6,166 depending on where you live.

There is one genuine reprieve for a true first year. The prior-year safe harbour is computed on last year's tax, so someone who was employed the whole of the previous year and paid $5,000 then can pay that amount across this year and settle the rest in April without penalty. The tax is still owed; the penalty is not. Knowing that turns a cash-flow emergency into a planning problem.

The habit that prevents the whole thing takes an afternoon to set up: a second bank account, a standing rule to move a fixed percentage of every payment into it on arrival, and the four dates in the calendar with a reminder a week before each. People who do this find estimated payments boring, which is the correct outcome.

And keep the records as you go rather than reconstructing them. The deductions in the section above are only worth what you can document, and the difference between a shoebox and a spreadsheet is usually several thousand dollars of legitimate deductions that never got claimed.

Five ways a self-employment estimate goes wrong

Calculating on revenue rather than profit. Self-employment tax applies to what is left after business expenses. Entering what you invoiced rather than what you kept overstates the bill by the whole of your cost base.

Forgetting the two adjustments. Only 92.35% of profit is subject to the tax, and half of what you pay is deductible against income tax. Skipping both overstates the result by several hundred dollars on a typical profit — $5,652 of deduction on $80,000.

Treating self-employment tax as an income tax bracket. It is a flat charge on profit that sits alongside income tax, not inside it. Someone in the 22.00% bracket does not pay 22.00% in total; on $80,000 the combined effective rate here is 20.81%.

Missing the QBI deduction. Up to 20% of qualified business income, worth $11,650 at this profit level, and claimed on the return rather than applied automatically by anything.

Assuming a Social Security ceiling that has already been used. If you also have a salary, the $184,500 wage base is shared between the two. Someone earning that much on a payroll pays no further Social Security on self-employment profit — only Medicare, which has no ceiling — and a calculator that does not ask about wages will overstate their bill substantially.

What Schedule C actually asks for

Self-employment income is reported on Schedule C, which is a profit and loss statement in tax form: gross receipts at the top, categories of expense beneath, and net profit at the bottom. That bottom figure is what flows to both self-employment tax and income tax.

Gross receipts means everything received for the work, whether or not a 1099 was issued for it. Clients are only required to issue one above a threshold, and cash payments frequently carry none — none of which changes that the income is reportable. Reporting only what appeared on forms is the most common form of underreporting and the easiest to detect, because the forms are filed with the IRS as well as sent to you.

The expense categories are prescribed rather than free-form: advertising, car and truck, contract labour, depreciation, insurance, interest, legal and professional, office, rent, repairs, supplies, taxes and licences, travel, meals, utilities and wages, plus a line for anything else. Putting an expense in a sensible category matters less than claiming it, but wildly miscategorised expenses invite questions.

A loss is permitted and is not itself suspicious. Businesses lose money, particularly early. What draws attention is a pattern of losses year after year with no plausible path to profit, because that starts to look like a hobby — and hobby losses are not deductible against other income at all.

The threshold for owing self-employment tax is $400 of net earnings, a figure that has not moved since 1990. Below it there is no self-employment tax, though the income is still subject to income tax and still has to be reported.

The same profit at three levels

Self-employment tax is close to flat, income tax is progressive, and the QBI deduction moves with both — so the combined rate behaves differently at each level.

On $30,000 of profit: $4,239 of self-employment tax and $942 of income tax, $5,181 in total — an effective 17.27%. At this level self-employment tax is far larger than income tax, because the standard deduction shelters most of the profit from income tax and shelters none of it from self-employment tax.

On $80,000: $11,304 and $5,344, $16,647 in total, an effective 20.81%. The two are now comparable in size.

On $200,000: $28,234 and $25,196, $53,431 in total, an effective 26.72%. Income tax now dominates, and the Social Security portion of self-employment tax has stopped climbing because the profit has passed the $184,500 wage base — only Medicare continues.

That last effect is why the combined effective rate rises more slowly than the income tax brackets alone suggest at higher profits, and why the S-corp election becomes less compelling above the wage base than it is below it: there is less Social Security left to save.

The records that make a deduction survive

A deduction is worth what you can document. The rule is not that receipts must be perfect, but that the amount, the date, the business purpose and the business relationship must be establishable — and reconstructing that from memory two years later rarely persuades anyone.

Mileage requires a contemporaneous log: date, destination, purpose and distance. An estimate produced after the fact is the single most commonly disallowed deduction, and the standard rate is generous enough that keeping the log is well paid work.

Meals require the business purpose and who was present, and the deductible proportion is limited. A meal eaten alone while working is not deductible at all, however genuinely it was during business hours.

The home office requires exclusive and regular use of a defined space. Exclusive is strict — a room used as an office and as a spare bedroom does not qualify, and this is the test that most home office deductions actually fail on rather than on the calculation.

Everything gets easier with a separate bank account and card used for nothing else. It is not legally required for a sole proprietor, and it is the single highest-return administrative decision available: it converts an annual reconstruction exercise into a categorisation exercise, and it is what makes the difference between claiming everything you are entitled to and claiming what you happen to remember.

Questions

How much tax do I pay on $80,000 of self-employment income?

About $16,647 in federal tax: $11,304 of self-employment tax and $5,344 of income tax after the standard deduction of $16,100, the $5,652 deduction for half the self-employment tax, and a QBI deduction of $11,650. Your state may take more on top. The same money as a salary would cost $14,890.

What is the self-employment tax rate?

15.30% — 12.40% for Social Security and 2.90% for Medicare. It applies to 92.35% of your net profit, and the Social Security half stops above $184,500 of combined wages and self-employment earnings. Medicare has no ceiling.

How much should I set aside from each payment?

At $80,000 of annual profit the federal effective rate is about 20.81%, so setting aside 30% covers federal comfortably in most cases. Add your state's rate on top — that ranges from nothing to about 10% depending on where you live. Move it to a separate account the day each payment arrives rather than at quarter end.

When are quarterly taxes due?

15 April, 15 June, 15 September, and 15 January of the following year, shifting to the next business day when one falls on a weekend or holiday. Note they are not evenly spaced — the second is two months after the first, not three, which is the deadline people most often miss.

Do I owe self-employment tax on a small side income?

Yes, above $400 of net earnings for the year — a threshold that has not been adjusted since 1990. Below that you owe no self-employment tax, though the income is still subject to income tax. There is no exemption for it being a hobby, a side project or paid in cash.

Can I reduce self-employment tax with a retirement contribution?

No. Self-employment tax is charged on net profit before any retirement contribution, so a SEP-IRA or solo 401(k) reduces your income tax and not this. It is the same asymmetry an employee meets: a 401(k) contribution does not reduce FICA either. What contributions can do is pull taxable income below the QBI threshold, which is often worth more than the direct saving.