Schedule C — Complete Practitioner Guide

What Is Schedule C?

Schedule C (Form 1040), Profit or Loss from Business, is the IRS form used by sole proprietors, freelancers, independent contractors, and single-member LLCs (treated as disregarded entities) to report business income and expenses. The net profit or loss from Schedule C flows directly to Form 1040 and is subject to both income tax and self-employment (SE) tax.

In 2026, approximately 27 million Schedule C returns are filed annually — making it the most common business tax form in the United States. The average Schedule C filer has $50,000–$150,000 in gross receipts and $30,000–$80,000 in net profit. The self-employment tax on that net profit — 15.3% on the first $176,100 — is the single largest tax burden for most sole proprietors, and the primary reason the S-Corp election is so valuable.

This guide covers every major Schedule C issue: deductible expenses, vehicle rules, home office, meals, depreciation, SE tax calculation, QBI deduction, hobby loss rules, and the audit triggers that the IRS uses to identify returns for examination.

Schedule C Deductible Expenses: Line by Line

Schedule C Part II lists the deductible business expenses. Every expense must be "ordinary and necessary" under IRC §162 — ordinary means common in the trade or business, and necessary means appropriate and helpful for the business. Here are the key lines and what practitioners need to know:

Self-Employment Tax: The Hidden Cost of Schedule C

The self-employment tax is the most significant tax burden for most Schedule C filers — and the most compelling reason to consider the S-Corp election. SE tax is 15.3% on the first $176,100 of net self-employment income in 2026 (12.4% Social Security + 2.9% Medicare), and 2.9% on net SE income above $176,100. An additional 0.9% Medicare surtax applies to net SE income above $200,000 (single) or $250,000 (MFJ).

For a sole proprietor with $150,000 in net profit, the SE tax is approximately $21,195 — before income tax. This is the equivalent of both the employee and employer portions of FICA tax, because a sole proprietor is both the employer and the employee.

The deductible portion of SE tax (50%) is deducted on Schedule 1 of Form 1040 as an above-the-line deduction, reducing AGI. This reduces income tax but does not reduce SE tax. The only way to reduce SE tax is to reduce net self-employment income — either through legitimate business deductions or by electing S-Corp status and paying a reasonable salary.

The QBI Deduction on Schedule C Income

Schedule C net profit qualifies for the §199A qualified business income (QBI) deduction at 23% in 2026 — made permanent by the One Big Beautiful Bill Act (OBBBA). For taxpayers below the income phase-out threshold ($201,750 single / $403,500 MFJ in 2026), the deduction is simply 23% of qualified business income (net profit minus the deductible portion of SE tax minus the self-employed health insurance deduction).

Above the phase-out threshold, the QBI deduction may be limited by W-2 wages and the unadjusted basis of qualified property. For sole proprietors above the threshold, the W-2 wage limitation can significantly reduce or eliminate the QBI deduction — because sole proprietors pay no W-2 wages to themselves. This is another reason the S-Corp election is valuable for high-income sole proprietors: the S-Corp pays W-2 wages to the owner, which count toward the W-2 wage limitation for QBI purposes.

Specified service trades or businesses (SSTBs) — including health, law, accounting, financial services, consulting, and athletics — are phased out of the QBI deduction above the income threshold. This means high-income doctors, lawyers, accountants, and consultants who file Schedule C may not qualify for the QBI deduction at all.