Sole Proprietor Tax Calculator
Running a business as a sole proprietor means your business income is taxed as personal income, plus you owe self-employment tax on your net earnings. This sole proprietor tax calculator estimates your total tax liability including self-employment tax (Social Security and Medicare), federal income tax, and quarterly estimated payments. Whether you're in your first year of business or an established sole trader, enter your business revenue and expenses below to understand your tax obligations and plan your cash flow.
How This Calculation Works
As a sole proprietor, your net business income (revenue minus expenses) is subject to both self-employment tax and federal income tax. The SE tax base is 92.35% of net income, taxed at 15.3% (12.4% Social Security on earnings up to $184,500 + 2.9% Medicare). Half of your SE tax is deductible when calculating adjusted gross income. Federal income tax is then computed on your taxable income after the SE deduction and the standard deduction ($16,100 for single filers, 2026) using progressive brackets from 10% to 37%.
What a Sole Proprietorship Is — and Isn't
A sole proprietorship is the default US business structure: if you earn business income in your own name and have not filed to become a corporation or partnership, you already are one. There is no separate tax return. Profit flows onto Schedule C of your personal Form 1040 and is taxed at your individual rates, plus self-employment tax of 15.3% on 92.35% of net profit.
| Structure | Tax return | Liability | Payroll tax on profit |
|---|---|---|---|
| Sole proprietor | Schedule C on Form 1040 | Personal, unlimited | Full 15.3% self-employment tax |
| Single-member LLC | Schedule C (unless elected otherwise) | Limited by the LLC | Full 15.3% self-employment tax |
| S-corporation | Form 1120-S plus K-1 | Limited | Only on the W-2 salary portion |
A single-member LLC changes your legal liability but, by default, nothing about your taxes — a distinction that surprises many owners who form an LLC expecting a tax cut.
Schedule C Line by Line
Schedule C converts business activity into a single profit figure. Getting the categories right protects the deductions if you are ever asked to substantiate them.
- Part I — gross receipts from all sources, including cash and payments never reported on a 1099.
- Cost of goods sold — inventory, materials and direct labour for product businesses.
- Part II expenses — advertising, contract labour, insurance, professional fees, office costs, rent, repairs, supplies, taxes and licences, travel, utilities.
- Vehicle expenses — standard mileage or actual costs, with a written log either way.
- Part V — other expenses, where software subscriptions, bank fees and merchant processing usually sit.
- Net profit — the figure carried to Form 1040 and to Schedule SE.
A loss can offset other household income, but repeated losses in an activity with personal enjoyment characteristics invite the hobby-loss rules, which disallow the deduction entirely.
Home Office, Vehicle and Mixed-Use Costs
Home office
The space must be used regularly and exclusively for business. The simplified method allows $5 per square foot up to 300 sq ft. The actual-expense method deducts a business percentage of rent or mortgage interest, property tax, utilities, insurance and repairs — usually larger for people paying high housing costs.
Vehicle
Standard mileage is simpler and better for economical, high-mileage vehicles. Actual expenses (fuel, insurance, depreciation, maintenance) suit expensive vehicles with lower mileage. You must choose in the first year of using the vehicle for business, which limits switching later.
Phone, internet, and equipment
Deduct only the business percentage of shared services. Equipment can often be expensed immediately under Section 179 or bonus depreciation rather than depreciated over several years.
Setting the Business Up Properly
- Get an EIN — free from the IRS, and it stops you handing your Social Security number to every client.
- Open a dedicated business bank account and use it for every business transaction.
- Check state and city requirements: DBA registration, sales-tax permit, local business licence.
- Register for sales tax if you sell taxable goods or services, including through online marketplaces.
- If you hire anyone, decide correctly between employee (W-2, withholding) and contractor (1099-NEC) — misclassification penalties are severe.
- Carry general liability or professional liability insurance, since your personal assets are exposed.
Paying Yourself and Paying the IRS
A sole proprietor does not take a salary. Transfers from the business account to your personal account are "owner's draws" and are not deductible; you are taxed on profit whether you withdraw it or not. Because of that, tax must be funded deliberately.
- Move 25–30% of every payment received into a separate tax savings account the same week.
- Pay quarterly estimates around 15 April, 15 June, 15 September and 15 January.
- Use the prior-year safe harbour (100%, or 110% if AGI exceeded $150,000) when income is unpredictable.
- Revisit an S-corporation election once profit is consistently above roughly $80,000–$100,000.
Estimate the instalments with the quarterly tax calculator, and compare the self-employment tax burden across structures with the self-employed tax calculator.