Federal income tax on a sole proprietorship is paid by the owner, not the business. You report the business’s profit or loss on Schedule C, carry the net figure to your Form 1040, and pay ordinary income tax at your marginal rate (up to 37% for 2026) plus a 15.3% self-employment tax on most of that same profit. There is no separate business return. Several deductions, most notably the 20% qualified business income deduction and the write-off for half of your self-employment tax, can pull the effective rate down meaningfully.
Why There Is No Separate Business Return
A sole proprietorship is not a taxpaying entity. Every dollar of net profit flows through to the owner’s Form 1040 and is taxed once at the individual’s marginal rate.1Internal Revenue Service. Forming a Corporation Whether you withdraw the money to a personal account or leave it sitting in a business account makes no difference. The IRS treats it as your income the moment it’s earned.
That single layer of tax is the defining feature of pass-through treatment, which also covers S corporations, partnerships, and most LLCs. The tradeoff is that a sole proprietor pays both halves of Social Security and Medicare tax, while a W-2 employee splits that cost with an employer.
Reporting Profit on Schedule C
Schedule C (Form 1040) is where the calculation starts.2Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship) Part I reports gross receipts from sales and services, less returns and allowances, to arrive at gross income. If you carry inventory, Part III walks through cost of goods sold. Part II lists operating expenses: supplies, rent, advertising, insurance, contract labor, and similar costs. The net figure on line 31 flows to Schedule 1 of Form 1040 for income tax purposes and to Schedule SE for self-employment tax.3Internal Revenue Service. Instructions for Schedule C (Form 1040)
Every expense you deduct has to be “ordinary and necessary” for your trade or business.4Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses Ordinary means common in your industry; necessary means helpful and appropriate. You don’t need to show the cost was indispensable, but you do need documentation of what it was and how it connected to the business.
Self-Employment Tax
Self-employment tax funds Social Security and Medicare. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.5Internal Revenue Service. Topic No. 554, Self-Employment Tax In a W-2 job, employer and employee each cover half. A sole proprietor pays both halves. The tax applies once your net earnings from self-employment reach $400 for the year.6Office of the Law Revision Counsel. 26 USC 1402 – Definitions
The tax isn’t calculated on your full net profit. You first multiply by 92.35%, which mirrors the fact that W-2 workers don’t pay FICA on the employer’s share of payroll taxes.5Internal Revenue Service. Topic No. 554, Self-Employment Tax So $80,000 of Schedule C profit becomes a $73,880 self-employment tax base, producing roughly $11,303 in self-employment tax.
The 12.4% Social Security piece stops at the annual wage base, which is $184,500 for 2026.7Social Security Administration. Contribution and Benefit Base Earnings above that cap keep paying the 2.9% Medicare portion, which has no ceiling. If your self-employment income tops $200,000 (single) or $250,000 (married filing jointly), an additional 0.9% Medicare tax applies to the excess and is reported on Form 8959.8Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
Deductions That Lower the Bill
Home Office
If you use a dedicated space in your home regularly and exclusively for business, you can claim a home office deduction. The simplified method allows $5 per square foot up to 300 square feet, for a maximum of $1,500.9Internal Revenue Service. Simplified Option for Home Office Deduction The regular method takes the business-use percentage of your home and applies it to actual costs like rent or mortgage interest, utilities, insurance, and property taxes. More paperwork, often a bigger deduction.
Vehicle Expenses
Business driving is deductible under either the standard mileage rate or actual expenses, but you have to pick one per vehicle per year. The 2026 standard mileage rate is 72.5 cents per mile.10Internal Revenue Service. The Standard Mileage Rates and Maximum Automobile Fair Market Values Have Been Updated for 2026 A contemporaneous log recording date, destination, purpose, and miles for each trip is what the IRS expects if the deduction is questioned. Actual expenses require tracking gas, insurance, repairs, and depreciation, then applying the business-use percentage.
Self-Employed Health Insurance
Sole proprietors who pay their own health insurance can deduct 100% of premiums for themselves, their spouse, and dependents as an adjustment to income on Schedule 1. The premiums can’t also be claimed as itemized medical expenses on Schedule A.11Internal Revenue Service. Form 7206, Self-Employed Health Insurance Deduction Two limits: the deduction can’t exceed your net business profit, and you can’t claim it for any month you were eligible for an employer-sponsored plan (through your own job or a spouse’s).
Half of Self-Employment Tax
You get to deduct half of the self-employment tax you owe when computing adjusted gross income, and you don’t need to itemize to take it.12Office of the Law Revision Counsel. 26 USC 164 – Taxes – Section 164(f) The reasoning tracks employment tax: an employer’s share of payroll taxes is a deductible business expense, and you’re effectively playing both roles. On $100,000 of net profit, this alone can save more than $1,000 of income tax.
The 20% Qualified Business Income Deduction
Section 199A lets eligible sole proprietors deduct up to 20% of qualified business income before calculating income tax.13Internal Revenue Service. Qualified Business Income Deduction The deduction was originally scheduled to expire at the end of 2025 but was made permanent by the One Big Beautiful Bill Act. You can claim it whether you take the standard deduction or itemize. On $100,000 of qualified business income, a clean 20% deduction pulls $20,000 out of taxable income.
The deduction is capped at the lesser of 20% of your qualified business income or 20% of your total taxable income minus net capital gains. For most sole proprietors at moderate income levels, the math is that simple.
Complications appear at higher incomes. Businesses in fields like law, health care, accounting, consulting, financial services, and athletics are classified as specified service trades or businesses.14eCFR. 26 CFR 1.199A-5 – Specified Service Trades or Businesses and the Trade or Business of Performing Services as an Employee Below the phase-in threshold, they still get the full 20%. Inside the range, the deduction shrinks; above it, it disappears entirely for those service businesses. For 2026, the phase-in range starts near $201,750 for single filers and roughly double that for joint filers. Non-service businesses face a different limitation at the same income levels, based on W-2 wages paid and business property owned.
Quarterly Estimated Payments
No one withholds tax from your sole proprietorship income, so the IRS expects quarterly estimated payments on Form 1040-ES.15Internal Revenue Service. Estimated Taxes For the 2026 tax year, the four deadlines are April 15, June 15, and September 15 of 2026, and January 15, 2027.16Internal Revenue Service. 2026 Form 1040-ES Estimated Tax for Individuals You can skip the January payment if you file the return and pay any balance by February 1.
Missing an installment triggers a penalty computed as interest on the shortfall for the days it stays unpaid, using the federal underpayment rate set each quarter.17Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax Each quarter is penalized separately, so a missed first payment hurts more than a missed fourth.
Two safe harbors keep you out of penalty territory. You’re protected if your payments and withholding cover at least 90% of the current year’s tax, or at least 100% of the prior year’s total tax (110% if your prior-year adjusted gross income was over $150,000).18Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty The prior-year rule is useful when income swings, because it gives you a fixed target. You also avoid the penalty entirely if your final balance owed is under $1,000 after credits and withholding.
2026 Tax Brackets
Your net profit, after the QBI deduction and the deduction for half of self-employment tax, is taxed at the same marginal rates as any other individual income. The 2026 brackets and standard deduction amounts reflect inflation adjustments and the permanent rates under the One Big Beautiful Bill Act.19Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments from the One Big Beautiful Bill The standard deduction is $16,100 for single filers and $32,200 for married couples filing jointly.
- 10%: Up to $12,400 (single) / $24,800 (married filing jointly)
- 12%: $12,401 to $50,400 / $24,801 to $100,800
- 22%: $50,401 to $105,700 / $100,801 to $211,400
- 24%: $105,701 to $201,775 / $211,401 to $403,550
- 32%: $201,776 to $256,225 / $403,551 to $512,450
- 35%: $256,226 to $640,600 / $512,451 to $768,700
- 37%: Over $640,600 / Over $768,700
These are marginal rates. At $80,000 of taxable income as a single filer, only the amount above $50,400 is taxed at 22%; the first $12,400 is taxed at 10% and the next $38,000 at 12%. Layer in the 20% QBI deduction and the deduction for half of self-employment tax, and the effective rate on business income often lands well below the top bracket you technically reach.
If You Pay Contractors
If your sole proprietorship pays an independent contractor $2,000 or more during the 2026 tax year, you file Form 1099-NEC for those payments.20Internal Revenue Service. General Instructions for Certain Information Returns (2026) The threshold rose from $600 for tax years beginning after 2025, and it will start adjusting for inflation in 2027. The 1099-NEC must reach the contractor and the IRS by January 31 of the following year.
Before work starts, have each contractor return a completed Form W-9 with their taxpayer identification number. If a contractor doesn’t supply one, backup withholding may apply to their payments.
How Long to Keep Records
The IRS can audit returns for at least three years after filing, and longer in certain cases. Match your retention to those windows.21Internal Revenue Service. How Long Should I Keep Records
- Three years is the standard period for receipts, bank statements, and invoices supporting a filed return.
- Six years applies if you omit more than 25% of gross income from a return.
- Seven years applies if you claim a deduction for bad debt or worthless securities.
- Indefinitely if you don’t file a return for a given year.
- For business property, keep records until at least three years after you dispose of the asset, because you need the original cost basis to figure depreciation and gain or loss.
Returns filed early are treated as filed on the due date for these timelines. When the situation is borderline, keep the records longer. Storage costs less than reconstructing an audit trail.