A sole proprietor files a personal Form 1040 with two business attachments: Schedule C to report business profit or loss, and Schedule SE to calculate self-employment tax. Most sole proprietors also file Form 1040-ES during the year to make quarterly estimated tax payments, and a few additional forms come into play depending on which deductions you claim. Because a sole proprietorship is not a separate legal entity, there is no standalone business return. Everything flows through your individual 1040 and is taxed at the same rates as wages and other personal income.
Schedule C: Profit or Loss From Business
Schedule C is where your business income and expenses live. You list gross receipts, subtract allowable business expenses, and land on a net profit or net loss on line 31. That number then moves to Schedule 1 (Form 1040), line 3, and becomes part of your adjusted gross income. It also carries over to Schedule SE.
If you run more than one business as a sole proprietor, file a separate Schedule C for each. You cannot combine them.1Internal Revenue Service. Instructions for Schedule C (Form 1040) (2025) Schedule C also asks for a six-digit Principal Business Activity code that matches your industry; the code list appears at the end of the instructions, and picking the wrong one can flag your return.2Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship)
The form has dedicated lines for common expense categories, including advertising, insurance, office supplies, contract labor, professional services, rent, and utilities. Two deductions have their own rules worth knowing when you fill out the form. The home office deduction can be taken by the simplified method at $5 per square foot up to 300 square feet, for a maximum of $1,500, or by the regular method that applies your business-use percentage to actual home expenses.3Internal Revenue Service. Simplified Option for Home Office Deduction Vehicle expenses can be claimed using actual costs or the standard mileage rate, which is 72.5 cents per mile for business use in 2026.4Internal Revenue Service. Notice 2026-10, 2026 Standard Mileage Rates If you want the option to use the standard mileage rate in later years, you must choose it in the first year you use the vehicle for business.
Schedule SE: Self-Employment Tax
No employer is withholding Social Security and Medicare from your business earnings, so you pay both the employer and employee shares yourself. Schedule SE calculates what you owe. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.5U.S. Government Publishing Office. 26 USC 1401 – Rate of Tax
The tax does not hit your full net profit. You multiply your Schedule C net profit by 92.35% first to get net earnings from self-employment. For 2026, the 12.4% Social Security portion applies only to the first $184,500 of those net earnings; the 2.9% Medicare portion has no cap.6Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet If your net self-employment earnings exceed $200,000 ($250,000 if married filing jointly), an Additional Medicare Tax of 0.9% applies to the amount above the threshold.7Internal Revenue Service. Topic No. 560, Additional Medicare Tax
You must file Schedule SE if your net self-employment earnings are $400 or more. Half of the total self-employment tax you calculate on the form is then deductible as an adjustment to income on Schedule 1 (Form 1040), line 15, which lowers your income tax.8Internal Revenue Service. About Schedule SE (Form 1040), Self-Employment Tax
Form 1040-ES: Quarterly Estimated Tax Payments
Because no one is withholding tax for you, the IRS expects payments throughout the year through Form 1040-ES. You are required to make estimated payments if you expect to owe $1,000 or more in tax after subtracting withholding and credits.9Internal Revenue Service. Estimated Taxes
Payments are due in four installments:
- April 15 (for income earned January 1 through March 31)
- June 15 (April 1 through May 31)
- September 15 (June 1 through August 31)
- January 15 of the following year (September 1 through December 31)
If a due date falls on a weekend or holiday, it shifts to the next business day. You can pay through IRS Direct Pay, the Electronic Federal Tax Payment System, or by mailing a check with a 1040-ES voucher.10Internal Revenue Service. Estimated Tax
To avoid an underpayment penalty, your total payments and withholding must equal at least the smaller of 90% of your current-year tax or 100% of the prior-year tax shown on your return. The prior-year figure rises to 110% if your prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately).11Internal Revenue Service. Instructions for Form 2210 (2025)
Other Forms You May Need
Two additional forms come up often for sole proprietors, tied to specific deductions rather than to the business itself.
Form 7206 calculates the self-employed health insurance deduction. If you pay for health coverage for yourself, your spouse, your dependents, or your children under age 27, you can deduct 100% of the premiums, but not on Schedule C. The deduction is claimed on Schedule 1 (Form 1040), line 17, and Form 7206 shows the math. The plan has to be established under your business, and you cannot take the deduction for any month you were eligible for an employer-subsidized plan, including through a spouse’s employer.12Internal Revenue Service. Instructions for Form 7206 (2025)
Form 8995 or Form 8995-A claims the Section 199A qualified business income (QBI) deduction, which allows eligible sole proprietors to deduct up to 20% of net business income from taxable income. The deduction was made permanent by the One Big Beautiful Bill Act, signed into law in July 2025. For 2025, you could use the simpler Form 8995 if your taxable income before the QBI deduction was $197,300 or less ($394,600 if married filing jointly); above those thresholds, you use Form 8995-A. The thresholds are inflation-adjusted each year.13Internal Revenue Service. Instructions for Form 8995 (2025) The QBI deduction reduces income tax only. It does not reduce self-employment tax.
Filing Deadline and Extension
For calendar-year filers, Form 1040 with Schedules C and SE attached is due April 15. If the date falls on a weekend or legal holiday, it moves to the next business day.14Internal Revenue Service. When to File
Filing Form 4868 before April 15 gives you an automatic six-month extension, usually to October 15. The extension covers filing only, not payment. Any tax you owe is still due April 15, and interest starts accruing from that date on anything unpaid.15Internal Revenue Service. Application for Automatic Extension of Time To File U.S. Individual Income Tax Return
Records to Keep Behind the Forms
The forms are only as good as the records supporting them. Before filing, pull together:
- All 1099-NEC forms from clients who paid you $600 or more, plus your own records of other business income including cash and card payments.16Internal Revenue Service. Am I Required to File a Form 1099 or Other Information Return
- Receipts, invoices, and statements for deductible expenses.
- A contemporaneous mileage log if you use the standard mileage rate, or actual-expense records if you do not.
- Square footage figures for the home office deduction, or your actual home expenses under the regular method.
- Proof of health insurance premiums paid under the business, plus records of any months you were eligible for employer-subsidized coverage.
Keep everything for at least three years after filing, the standard IRS audit window. Some situations extend that to six years. A separate business bank account makes sorting deductible expenses from personal spending far easier.
Penalties for Filing or Paying Late
Missing deadlines triggers two penalties that can run at the same time. The failure-to-file penalty is 5% of the unpaid tax per month or partial month, capped at 25%.17Internal Revenue Service. Failure to File Penalty The failure-to-pay penalty is 0.5% of the unpaid tax per month, also capped at 25%. When both apply in the same month, the combined charge is 5%, because the failure-to-file penalty is reduced by the failure-to-pay amount.18Internal Revenue Service. Failure to Pay Penalty
If you cannot pay the full amount, file on time anyway. That eliminates the 5%-per-month penalty, and if you set up an approved payment plan, the failure-to-pay rate drops to 0.25% per month. Interest keeps accruing on any unpaid balance from the original due date until the tax is fully paid.18Internal Revenue Service. Failure to Pay Penalty