Who does the IRS actually audit?
The overall individual audit rate is low — around 0.2% to 0.4% of all returns. But that average hides enormous variation. Self-employed workers filing Schedule C are audited at rates several times higher than W-2 employees, especially once income crosses the $25,000 threshold. The reason is straightforward: self-employment involves judgment calls (which expenses to deduct, what percentage of a car is business use, whether a home office qualifies) that create potential for both honest mistakes and intentional underreporting. The IRS knows this and allocates scrutiny accordingly.
The IRS uses an automated scoring system called Discriminant Inventory Function (DIF) to flag returns for review. The exact formula is proprietary, but decades of tax practitioner experience have identified the patterns it catches: unusual expense ratios for your industry, deductions that deviate significantly from statistical norms for similar businesses, and structural red flags like no separation between personal and business finances.
Important context: Most IRS contacts are correspondence audits — a letter asking for documentation on one or two line items, not a full field examination. Organizing your records now means a correspondence audit takes an hour rather than a nightmare.
The five most common audit triggers for self-employed people
1. High expense-to-revenue ratio
The IRS compares your deductions to industry averages for businesses at your revenue level. If your expense ratio significantly exceeds the norm — particularly if expenses exceed 60–80% of gross revenue — the return scores higher on DIF. Legitimate high-expense businesses should document every deduction carefully; this is when receipts matter most.
2. Claiming 100% business vehicle use
Very few vehicles are exclusively used for business. Claiming 100% business use signals either a dedicated business vehicle (a delivery truck, for example) or an inflated deduction. Without a contemporaneous mileage log — one maintained throughout the year with dates, destinations, and business purposes — the deduction is nearly impossible to defend in an audit. The IRS is well aware of this and pursues it aggressively.
3. Repeated business losses
Showing a profit in fewer than 3 of the last 5 years can trigger review under IRC Section 183, the hobby loss rule. The presumption flips: the IRS assumes your activity is a hobby, and you must prove otherwise. Factors they examine include whether you depend on the income, the time and effort you devote to the business, your expertise, and your history of generating profit in similar activities.
4. Commingled personal and business funds
Operating without a dedicated business bank account creates two problems: it makes it harder to document business income and expenses accurately, and it signals to the IRS that the operation may be informal. During an audit, an examiner who sees personal and business transactions mixed together has more latitude to question what's deductible.
5. Cash-intensive businesses
Restaurants, cleaning services, landscaping, childcare, and similar cash-based businesses are statistically more likely to underreport income — and the IRS knows it. If your reported income seems low relative to your lifestyle or industry norms, the discrepancy can prompt a bank deposit analysis or lifestyle audit.
The best defense is a paper trail. An audit isn't automatically a problem if you have documentation. The businesses that face real penalties are the ones that can't substantiate their deductions — not simply the ones who took them.
What to do if your risk score is high
A high score on this estimator doesn't mean you'll be audited — it means your return has characteristics that the IRS pays attention to. The right response is documentation, not panic. Start with the biggest red flags first: if you claimed vehicle expenses, reconstruct your mileage log now. If you've had consecutive losses, write a brief memo documenting your business plan, the steps you've taken to improve profitability, and your intent to earn a profit.
If you're in a high-risk category, working with a CPA or enrolled agent is worth the cost. A professional who signs your return has skin in the game and will flag deductions that might not survive audit scrutiny before they ever appear on your return.