Schedule C for small business: the 2026 IRS filing guide

Schedule C — 'Profit or Loss From Business' — is the one-page IRS form that separates hobbies from real businesses. If you're a sole proprietor or single-member LLC filing as a disregarded entity, this attaches to your Form 1040 and summarizes everything your business did in the tax year.

Done right, Schedule C is how you capture every legitimate deduction, lower your taxable income, and avoid the audit triggers most first-time filers walk into. Done wrong, it's the fastest way to a CP2000 notice.

Who has to file Schedule C?

You file Schedule C if you're any of the following:

• Sole proprietor (including freelancers, consultants, Etsy sellers, rideshare drivers)
• Single-member LLC not electing S-corp or C-corp tax treatment
• A statutory employee with W-2 box 13 checked
• Husband-and-wife business treating as qualified joint venture (files two Schedule Cs, not a partnership return)

When is Schedule C due?

Schedule C is attached to Form 1040, so the deadline is the same — April 15 for the prior tax year. If you file an extension (Form 4868), you get until October 15 to file, but any tax owed is still due April 15 or you'll pay interest and penalties on the unpaid balance.

Schedule C section by section

Part I — Income

• Line 1: Gross receipts or sales — everything you brought in before expenses
• Line 2: Returns and allowances — refunds, credits, discounts
• Line 4: Cost of goods sold — carry over from Part III if you sell products
• Line 6: Other income — state tax refunds on prior deductions, interest on receivables

Part II — Expenses (this is where the money is)

The deduction categories most small businesses use:

Part III — Cost of Goods Sold (if you sell products)

The inventory math: beginning inventory + purchases − ending inventory = COGS. If you're a pure service business, you skip this section entirely.

Part IV — Vehicle information

If you're deducting car expenses, you fill in business/commuting/personal miles. The IRS audits this section more than any other on Schedule C — keep a contemporaneous mileage log (an app that auto-tracks works; a reconstructed one six months later does not).

Schedule C deductions most people miss

• Home office deduction — simplified method gives $5/sq ft up to 300 sq ft ($1,500 max), or use actual expense method for bigger deductions
• Business portion of internet and cell phone — audit-proof at 50–70% if you use them for business daily
• Startup costs — up to $5,000 in the first year, remainder amortized over 15 years
• Retirement plan contributions — SEP IRA, Solo 401(k) contributions reduce taxable income directly
• Qualified Business Income (QBI) deduction — up to 20% of net profit on top of Schedule C, reported on Form 8995

Red flags that trigger Schedule C audits

• Losses in 3 of 5 consecutive years — IRS may reclassify as a hobby and disallow all deductions
• Home office that doesn't pass exclusive + regular use test
• 100% business use of a vehicle without a mileage log
• Large round-number deductions ($5,000 in supplies, $10,000 in meals) — IRS pattern-matches these
• Gross receipts significantly higher than reported by third parties (1099-K, 1099-NEC)

How Wemu simplifies Schedule C

Wemu's Bookkeeper Agent categorizes every transaction against the Schedule C line items as it happens — advertising, supplies, rent, contract labor all sort into the right buckets automatically. At year-end, the Agent produces a pre-filled Schedule C summary ready to hand to your CPA, with every deduction already categorized and sourced.

Frequently asked questions