Small Business Taxes 101: What You Actually Owe
Self-employment tax kicks in at just $400 of net earnings. The safe-harbor rule can cap what you owe in estimates. A plain-English map of what you pay, when, and why.
Taxes are the part of business nobody warns you about until it's April and you owe a number that makes you feel faint. Here's how it actually works, so it never surprises you.
Educational only — not tax advice. Figures below are quoted from IRS guidance and several are adjusted annually, so check the current year before relying on any of them. A good accountant pays for themselves; this is your map so you know what they're talking about.
The taxes you'll actually pay
1. Income tax. You owe federal (and usually state) income tax on your business profit — not your revenue. Profit is what's left after expenses.
2. Self-employment tax. The big surprise for new owners, and the one worth understanding properly rather than as a single percentage. Details below.
3. Sales tax. If you sell products (and some services), you collect sales tax from customers and remit it to the state. It's not your money — you're holding it for the state, so never spend it.
4. Payroll tax. Only if you have employees.
Self-employment tax, decomposed
Most guides give you "15.3%" and stop. The structure underneath changes what you actually owe.
What the 15.3% is made of
The rate consists of "12.4% for social security (old-age, survivors, and disability insurance) and 2.9% for Medicare (hospital insurance)."
The Social Security half is capped. For 2024, "the first $168,600 of your combined wages, tips, and net earnings is subject to" it. Past that ceiling, the 12.4% stops.
The Medicare half is not capped. "All of your wages and tips are subject to the 2.9% Medicare part of the SE tax on all your net earnings" — there is no ceiling at all.
High earners pay more. An additional 0.9% Medicare Tax applies above $200,000 (single) or $250,000 (married filing jointly).
You file at $400. You must file if "your net earnings from self-employment (excluding church employee income) were $400 or more."
Two practical consequences fall out of that structure.
Your effective SE rate falls as you earn more, because the 12.4% portion stops at the wage base while the 2.9% continues. Someone well past the cap is paying a much lower marginal SE rate than someone below it — the opposite of how people usually assume tax works.
And $400 is genuinely the threshold. A weekend side project that nets a few hundred dollars crosses it. The arithmetic of what a side hustle actually earns after costs and hours matters partly because the tax obligation arrives long before the income feels significant.
The deduction that softens it
You "can deduct the employer-equivalent portion of your self-employment tax" — the employer share, which is half of the total. That deduction reduces your income for income-tax purposes (it does not reduce the SE tax itself).
So the headline 15.3% overstates the real bite. This is also exactly why the S-corp election exists as a planning option, and why a full walk through how self-employment tax is computed is worth reading before you decide your structure.
Quarterly estimated taxes
The IRS doesn't want to wait until April.
Who has to pay, and the rule that protects you
Individuals "generally have to make estimated tax payments if they expect to owe tax of $1,000 or more when their return is filed." For corporations the threshold is $500.
The year is divided into four payment periods. The exact due dates are published in Form 1040-ES — check it rather than working from memory, because they shift when a date falls on a weekend or holiday.
The safe harbor: most taxpayers avoid an underpayment penalty if they "owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller."
That last provision is the most useful sentence in this entire guide, and it's the one nobody tells new owners.
If you pay in 100% of what you owed last year, you're generally protected — even if this year is dramatically better. For a business that's growing fast, that's enormous: you don't have to forecast a boom accurately to avoid penalties. You have to cover a number you already know, because last year's return is sitting in a drawer.
There are special rules for farmers, fishermen, and certain higher-income taxpayers, which is exactly the kind of thing to raise with an accountant rather than infer.
The set-aside system
Every time money comes in, move 25–30% of the profit into a separate "taxes" savings account. Pay your quarterlies from it. April becomes a non-event.
Two refinements worth making:
- Set aside on profit, not revenue. Moving 30% of revenue starves the business; moving 30% of profit is the actual obligation.
- Check the percentage against reality once a year. 25–30% is a starting heuristic, not a computed figure — your bracket, your state, and your deductions all move it.
Write-offs (deductions) that are actually legit
A deduction lowers your taxable profit. Common legitimate ones:
- Home office (if used regularly and exclusively for business)
- Business use of your car (track the miles)
- Software, tools, and subscriptions
- Marketing and advertising
- Professional services (your accountant, lawyer)
- Business meals (partially deductible — the percentage has changed more than once, so check the current rule)
- Equipment and supplies
The rule: it must be ordinary and necessary for your business. "I bought a boat for vibes" is not a write-off.
Documentation is what makes a deduction survive scrutiny, and it has a shelf life — the IRS retention periods run from three years to indefinitely depending on circumstances, which a working bookkeeping habit handles as a matter of routine rather than as an annual scramble.
The 3 things that save you
- Separate business bank account — never commingle funds
- Set aside 25–30% of profit for taxes, automatically
- Use the safe harbor — cover 100% of last year's tax and stop trying to forecast this year perfectly
Do those three and taxes go from terrifying to tedious — which, in tax terms, is a win.
Frequently asked questions
I only made a few hundred dollars on the side. Do I really have to deal with this?
If net earnings from self-employment were $400 or more, the IRS filing requirement applies — that's the stated threshold, and it's low enough that a modest side project clears it. Whether you actually owe much is a separate question from whether you have to file, and the two get conflated constantly. If you're near the line, that's a short conversation with a tax professional rather than a guess.
If the safe harbor is based on last year, what do I do in my first year of business?
There's no prior-year return to anchor to, so the 100%-of-last-year route isn't available in the way it is later — which is precisely when the set-aside habit matters most, because you're estimating from scratch with no baseline. Being deliberately generous with the set-aside in year one costs you nothing but held cash, and getting it wrong costs a penalty.
Why does self-employment tax exist on top of income tax? It feels like double taxation.
It isn't double income tax — it's Social Security and Medicare, which an employee also pays. The difference is that an employee splits it with their employer, each covering half. Self-employed, you are both parties, so you cover both halves. The deduction for the employer-equivalent portion exists to acknowledge exactly that asymmetry.
Is forming an S-corp actually worth it to reduce self-employment tax?
Sometimes, and it depends on numbers this guide can't see. The mechanism is real — an S-corp lets you split earnings between salary (subject to employment taxes) and distributions (generally not) — but it brings payroll obligations, a reasonable-compensation requirement, filing costs and a March deadline instead of April. It tends to make sense above a certain profit level and to cost more than it saves below it. That threshold is genuinely specific to you.
It's just business — the government would simply like its cut, four times a year.
Sources
- IRS — Self-Employment Tax (Social Security and Medicare Taxes)
How this was checked
States the self-employment tax rate as 15.3%, consisting of '12.4% for social security (old-age, survivors, and disability insurance) and 2.9% for Medicare (hospital insurance).' For 2024, 'the first $168,600 of your combined wages, tips, and net earnings is subject to' the Social Security portion; the Medicare portion has no cap, with 'all of your wages and tips subject to the 2.9% Medicare part of the SE tax on all your net earnings.' An additional 0.9% Medicare Tax applies above $200,000 (single) or $250,000 (married filing jointly). Taxpayers 'can deduct the employer-equivalent portion' of the self-employment tax. The filing requirement applies if 'your net earnings from self-employment (excluding church employee income) were $400 or more.' Confirmed by direct fetch. The wage base is adjusted annually; the $168,600 figure is stated for 2024.
- IRS — Estimated Taxes
How this was checked
States that individuals 'generally have to make estimated tax payments if they expect to owe tax of $1,000 or more when their return is filed,' and that the corporate threshold is $500. Describes the safe harbor: most taxpayers avoid the underpayment penalty if they 'owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller.' Notes that special rules exist for farmers, fishermen and certain higher income taxpayers, directing readers to Publication 505. Confirmed by direct fetch. Note: this IRS page does not itself enumerate the four quarterly due dates, directing readers to Form 1040-ES instead, so no specific dates are asserted here.
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This article is educational and satirical content from Business Dog. It is not financial, legal, or tax advice. It's just business.