A Schedule C is where self employment income goes on your tax return. If you were paid for work and nobody withheld tax from it, this is usually the form that describes what you earned and what it cost you to earn it.
It is attached to your Form 1040 rather than filed on its own, and the number it produces flows into the rest of your return. That is the part people miss. A Schedule C is not a separate tax on a separate thing. It changes what you owe overall, and it changes it in two ways rather than one.
Who ends up filing one
You file a Schedule C if you carried on a trade or business as a sole proprietor. In practice, the people who arrive with one are most often contract software engineers and designers who have left a W-2 job and are now invoicing clients directly. The work has not changed. The tax treatment of it has, completely.
It also covers consulting, driving, selling online, and most paid work that is not an employee job.
A single member LLC that has not elected to be taxed as a corporation files a Schedule C as well. The LLC matters for liability, and it does not change where the income is reported. That surprises people, and it is worth knowing before forming one in the expectation of a tax result.
You file one per business. Two genuinely different businesses means two Schedule Cs.
What the form asks, in the order it asks it
Income, and what counts as income
The form opens with gross receipts. That is everything the business took in. Not the amount that landed in your account after fees, and not only the amounts that appeared on a 1099.
That second point causes the most trouble. A Form 1099-NEC or 1099-K is a report of some of your income, filed by somebody who paid you. It is not a statement of all of it. Income paid in cash, or by a client who never issued a form, is still income. The IRS matches the forms it received against what you reported, so a figure below the total of your 1099s is a question waiting to be asked. A figure above that total is normal.
Returns and allowances come off next, then cost of goods sold if you hold stock, and what remains is your gross profit.
Expenses, and the categories the form gives you
Part II is a list of expense categories, and the test for all of them is the same. The cost has to be ordinary and necessary for the business. Ordinary means it is the sort of expense a business like yours normally has. Necessary means it is helpful and appropriate, not that you could not have survived without it.
The categories are prescriptive: advertising, car and truck, contract labour, insurance, interest, legal and professional, office expense, rent, repairs, supplies, taxes and licences, travel, meals, utilities, wages, and a line for anything else. Much of the work of preparing a Schedule C is deciding which category a cost belongs in and staying consistent year to year.
Cost of goods sold, if you hold stock
If you buy or make things to sell, Part III works out what the goods you actually sold cost you, from opening stock, purchases, labour, materials and closing stock. If you sell services, you can skip it.
The point to understand is timing. Buying stock is not a deduction when you buy it. It becomes one when you sell it. A business that spent heavily on inventory in December can have a far smaller deduction that year than it expects.
The four expenses people get wrong most often
The home office, and the rent claimed with it. This is the one that comes up most. Somebody works from home, so they put the rent for the whole home on the Schedule C. The answer is that you can deduct rent, because the deduction is available to renters and not only to owners, but not all of it, and not automatically.
Two tests have to be met. The space must be used regularly and exclusively for the business, and your home must be your principal place of business. Exclusively is the word that decides most cases. A room you also eat in, sleep in, or keep the exercise bike in does not qualify, however much work happens there. What you then deduct is the business use percentage, worked out from the share of your home’s square footage the office takes up. There is also a simplified option that applies a set rate per square foot instead of tracking actual costs.
So the honest version is: yes to rent, no to all of it, and only if that space is used for nothing else.
The car. You can use the standard mileage rate or your actual costs, and the choice carries consequences into later years. The business rate was 70 cents a mile for 2025. For 2026 it changed partway through the year: 72.5 cents a mile from 1 January to 30 June, and 76 cents a mile from 1 July to 31 December. A single 2026 log therefore has two rates applied to it, split at the end of June. Either method needs a record of business miles kept at the time, not reconstructed afterwards.
Meals. Generally limited to 50 percent of the cost, with narrow exceptions. Entertainment is a separate question and is treated far less generously.
Clothing. Almost never deductible. The test is whether it is suitable for everyday wear, and if it is, the answer is no, however strictly your work requires it.
Your own health insurance and retirement contributions are often deductible, but not here. They go elsewhere on the return, and putting them on the Schedule C understates your self employment income while overstating the deduction.
What a Schedule C does to the rest of your return
Self employment tax
This is the part that surprises people, and it is why a Schedule C deserves planning rather than being filled in at the end.
An employee and their employer each pay half of Social Security and Medicare. Self employed, you are both, so you pay both halves. The rate is 15.3 percent, being 12.4 percent for Social Security and 2.9 percent for Medicare, and it is worked out on Schedule SE.
Three details matter. It is charged on 92.35 percent of your net profit rather than all of it. It starts once net earnings from self employment reach 400 dollars. And the 12.4 percent Social Security portion stops at the wage base, which was 176,100 dollars for 2025 and is 184,500 dollars for 2026, while the 2.9 percent Medicare portion has no ceiling at all. Above 200,000 dollars for a single filer, or 250,000 joint, a further 0.9 percent Additional Medicare Tax applies.
It is charged whether or not you owe any income tax. Somebody whose deductions leave them with no income tax liability can still owe self employment tax on the same profit. Half of it is deductible against your income tax, which softens the result without removing it.
Somebody who has just left a W-2 job should set aside more than they expect, and more than income tax alone would suggest, because self employment tax sits on top of it.
Estimated payments
The harder change is not the amount. It is that nobody is collecting it for you.
In a W-2 job the tax left before the money reached you. Self employed, the whole invoice arrives and the tax has to be paid out of your own account, in instalments across the year, on dates you are responsible for remembering. Missing those payments produces a penalty even where you pay everything you owe by the filing deadline.
One thing worth knowing if you have a spouse in a W-2 job: withholding is treated as paid evenly across the year, whenever it actually happened. Increasing it can repair an underpayment that estimated payments alone cannot, because a late estimated payment stays late.
Records that make this straightforward
You do not need an accounting system. You need a separate bank account.
Business income into the business account, business costs out of it, personal spending on the personal account, and no crossing over. That one habit does most of the work, because it turns your records into a statement you already receive and it removes the question that takes the longest to answer afterwards, which is whether a particular payment was business or not.
Beyond that, keep receipts for anything you would struggle to explain from a bank line alone, and keep a contemporaneous record of business mileage.
The reason to care is not tidiness. A deduction you cannot substantiate is one you may lose if the return is examined, and reconstructing a year afterwards is slower and more expensive than keeping it as you go.
When a Schedule C stops being the right answer
As profit grows, self employment tax on all of it becomes the largest part of the bill, and an S corporation election starts to be worth modelling. It brings payroll, a separate return, and a requirement to pay yourself reasonable compensation, and each of those has a cost. A late S corporation return has a penalty of its own, charged per shareholder per month, which is worth knowing before taking on the extra filing.
Before any of that, there is a question that is not about the maths at all.
An S corporation has eligibility rules, and they rule some businesses out entirely. Shareholders may not be partnerships, corporations, or non-resident aliens. There can be no more than 100 of them, and the company may have only one class of stock.
Two situations run straight into that. If you have a foreign shareholder, an S corporation is not available, whatever the numbers say. And if you expect to raise investment, it is usually not available either: investors are frequently partnerships or corporations, which cannot hold the stock, and preferred stock is a second class of stock, which breaks the one class rule on its own.
So the order of the questions is: can this business be an S corporation at all, and only then, is it worth it. It is a calculation rather than a rule of thumb, and it is worth doing before a year begins rather than after it ends.
If you are not a US citizen
This changes the largest number on the page, and it is the part most general guidance skips.
A nonresident alien is not subject to self employment tax. Not by treaty, and not by election. It is the default position: individuals who are neither citizens nor residents of the United States are outside the tax entirely. Somebody filing a nonresident return on self employment income can find that the 15.3 percent described above simply does not apply to them.
Two things qualify that, and both run in directions people do not expect.
The first is that a totalization agreement, which the United States has with a number of countries to stop the same earnings being charged twice, can work the other way. Rather than exempting a nonresident, it can assign social security coverage to the United States and make that person liable for self employment tax who otherwise would not have been.
The second is residency itself. Once you become a resident alien, self employment tax applies on the same terms as it does to a citizen, and it reaches self employment income received after that point even where the work was performed while you were still a nonresident.
Which of these you are is decided by the substantial presence test rather than by your visa. It is worth settling before you file, because it is the difference between owing self employment tax and not owing it at all.
Having it prepared
Individual returns with a Schedule C are on the published fee list, with the fee confirmed in writing before any work starts. You can see what that covers on the individual returns page, or describe your situation and get a straight answer about whether it is straightforward.