If you own a single-member LLC, you file Schedule C for the LLC as an attachment to your personal Form 1040. The IRS treats a single-member LLC as a “disregarded entity” by default, so the business itself files no separate income tax return. Every dollar of profit flows through to your 1040 and gets taxed there, along with self-employment tax for Social Security and Medicare.
When Your LLC Actually Uses Schedule C
Federal tax classification, not state registration, decides which form you file. A single-member LLC is automatically disregarded for federal income tax purposes unless the owner files Form 8832 to elect corporate treatment.1Internal Revenue Service. Single Member Limited Liability Companies Disregarded status means the IRS looks through the LLC to you and treats the activity as a sole proprietorship. Income and expenses go on Schedule C, filed with your Form 1040.2Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship)
A spouse-owned LLC can qualify. If you and your spouse jointly own and operate the LLC and both materially participate, you can elect qualified joint venture treatment. Each spouse files a separate Schedule C for their share of income and expenses instead of a partnership return on Form 1065.3Internal Revenue Service. Election for Married Couples Unincorporated Businesses
Schedule C does not apply if your LLC has multiple members that are not a spousal joint venture (it defaults to partnership taxation on Form 1065), or if you elected S-corporation or C-corporation treatment. An S-corp files Form 1120-S, and the owner is paid through W-2 wages and a Schedule K-1 rather than Schedule C.4Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation
Working Through the Three Parts of Schedule C
Schedule C is organized into three main parts, and working them in order keeps the math clean.
Part I — Income. Enter gross receipts on Line 1, which should tie to your records of cash, checks, electronic transfers, credit card sales, and any 1099-NEC or 1099-K forms you received. Subtract returns and allowances. If you sell products, subtract cost of goods sold (from Part III) to get gross profit.
Part III — Cost of Goods Sold. Complete this section only if your business sells physical products. Enter beginning inventory, add purchases and labor, subtract ending inventory, and carry the resulting COGS back to Part I.
Part II — Expenses. Enter totals for each named category: advertising, insurance, office expenses, rent, utilities, wages paid to employees, and so on. Depreciation from Form 4562 goes on Line 13. Anything that doesn’t fit a named line goes on Line 27 with an itemized breakdown in Part V.
After totaling expenses in Part II and subtracting them from gross profit, Line 31 gives you net profit or loss. That figure drives the rest of your return: it moves to Schedule 1 as income and to Schedule SE as the base for self-employment tax.5Internal Revenue Service. Schedule C (Form 1040) – Profit or Loss From Business
Deductions That Change What You Owe
Vehicle Expenses
If you use a vehicle for business, choose one of two methods. The standard mileage rate for 2026 is 72.5 cents per business mile.6Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile, Up 2.5 Cents The alternative is tracking actual expenses (gas, insurance, repairs, depreciation) and deducting the business-use percentage. Either way, keep a mileage log or receipts. Actual expenses sometimes produce a larger deduction for vehicles with high operating costs.
Home Office
You can claim a home office deduction if you use part of your home exclusively and regularly as your principal place of business.7Internal Revenue Service. Instructions for Form 8829, Expenses for Business Use of Your Home “Exclusively” is strict: a desk in a room where you also watch TV won’t qualify.
The simplified method gives you $5 per square foot of dedicated office space, up to 300 square feet, for a maximum deduction of $1,500.8Internal Revenue Service. Simplified Option for Home Office Deduction The regular method, filed on Form 8829, deducts the business-use percentage of actual mortgage interest or rent, utilities, insurance, and repairs. More recordkeeping, often a larger deduction.
Depreciation and Section 179
Equipment, furniture, and other assets that last more than a year are usually depreciated over their useful life on Form 4562, with the total feeding Schedule C, Part II.9Internal Revenue Service. About Form 4562, Depreciation and Amortization Section 179 offers a shortcut: you can expense the full cost of qualifying property in the year you place it in service. For 2026, the cap is $2,560,000 in qualifying assets, and the deduction begins phasing out once total qualifying property placed in service exceeds $4,090,000.
Start-Up Costs
A new LLC can deduct up to $5,000 in start-up costs in its first year. That allowance shrinks dollar-for-dollar once total start-up costs pass $50,000 and disappears at $55,000. Anything you can’t deduct immediately is amortized over 180 months beginning the month the business starts operating.10Office of the Law Revision Counsel. 26 USC 195 – Start-Up Expenditures Start-up costs include market research, travel to find suppliers, and pre-launch advertising.
Self-Employment Tax on the Net Profit
The net profit on Schedule C Line 31 is the starting point for self-employment tax, which covers your share of Social Security and Medicare. There is no employer to split it with, so you pay both halves. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.11Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
Schedule SE first multiplies net earnings by 92.35% before applying the tax.12Internal Revenue Service. 2025 Schedule SE (Form 1040) The 12.4% Social Security portion applies only up to $184,500 in net earnings for 2026.13Social Security Administration. Contribution and Benefit Base The 2.9% Medicare portion has no cap. An additional 0.9% Medicare surtax applies to earnings above $200,000 for single filers or $250,000 for joint filers.14Internal Revenue Service. Topic No. 560 – Additional Medicare Tax
The SE tax then lands on Schedule 2 of Form 1040.15Internal Revenue Service. Schedule 2 (Form 1040) – Additional Taxes You get to deduct half of it as an adjustment to income on Schedule 1, which reduces your adjusted gross income and, through it, your income tax.16Internal Revenue Service. Topic No. 554, Self-Employment Tax
The Qualified Business Income Deduction
Section 199A lets many single-member LLC owners deduct up to 20% of their qualified business income on top of everything else.17Internal Revenue Service. Qualified Business Income Deduction The deduction was originally set to expire after 2025 and has been extended. Claim it on Form 8995, or Form 8995-A for higher earners.
Below the income thresholds, the math is simply 20% of net QBI from Schedule C. For 2026, wage-and-property limitations begin phasing in around $201,750 in taxable income for single filers and $403,500 for joint filers. Above those ranges, the deduction may be reduced or eliminated depending on the type of business and the wages it pays.
How Schedule C Feeds Your Form 1040
Two supporting schedules connect Schedule C to your 1040. Net profit or loss from Line 31 goes to Schedule 1, where it joins any other income to build adjusted gross income; the half-of-SE-tax deduction also lives on Schedule 1.18Internal Revenue Service. Schedule 1 (Form 1040) – Additional Income and Adjustments to Income Total self-employment tax from Schedule SE goes to Schedule 2, where it is added to your income tax.15Internal Revenue Service. Schedule 2 (Form 1040) – Additional Taxes
A complete filing usually includes Form 1040, Schedule C, Schedule SE, Schedule 1, Schedule 2, and any supporting forms such as Form 4562 for depreciation or Form 8829 for the regular home office method. Everything files together as one return.
Paying as You Go
No paycheck means no withholding, and the IRS wants its money throughout the year, not in one April payment. You’re generally required to make estimated tax payments if you expect to owe $1,000 or more after subtracting withholding and refundable credits.19Internal Revenue Service. Estimated Tax – Individuals The 2026 deadlines are:
- April 15, 2026, for income earned January through March
- June 15, 2026, for April and May
- September 15, 2026, for June through August
- January 15, 2027, for September through December
You can skip the January 15 payment if you file your full 2026 return and pay the balance by February 1, 2027.20Internal Revenue Service. 2026 Form 1040-ES To avoid an underpayment penalty, your total estimated payments and withholding should cover at least 90% of the current year’s tax or 100% of the prior year’s tax (110% if your AGI exceeded $150,000).19Internal Revenue Service. Estimated Tax – Individuals Many owners base their first year of payments on prior-year figures and adjust once the business’s earning pattern is clearer.
Mistakes That Draw Scrutiny
A few patterns reliably create trouble. Round expense numbers signal estimation rather than real records: $5,000 in office supplies and $3,000 in travel, each perfectly clean, tells the IRS you didn’t track actual spending.
Failing to report income shown on 1099s is another fast route to a notice. The IRS receives copies of every 1099-NEC and 1099-K sent to you, and its matching system flags returns where reported income falls short. If a 1099 overstates what you actually received, resolve it before you file, not after a letter arrives.
The accuracy-related penalty for underpayment due to negligence is 20% of the underpaid amount, on top of the tax owed and interest.21Internal Revenue Service. Accuracy-Related Penalty A separate business bank account, real-time bookkeeping, and organized receipts by category are the plain defenses against both audit exposure and careless math. The IRS generally recommends keeping business records for at least three years after filing, and employment tax records for four.22Internal Revenue Service. Taking Care of Business: Recordkeeping for Small Businesses