What Really Triggers an IRS Audit? 7 Tax Mistakes Dentists Need to Avoid

If you think taking tax deductions is what gets people audited, you are not alone — and you are wrong. The IRS does not audit you for trying to lower your tax bill. The IRS audits you when your return looks like it cannot be defended. That usually means aggressive positions, sloppy records, inconsistent numbers, or income that does not match the forms the IRS already has.

What audits actually look like

Most IRS audits are not dramatic. Nearly 78% are handled by mail. The overall individual audit rate is around 0.3%, but that number climbs significantly as income rises. For taxpayers reporting $10 million or more, the audit rate is about 11%. And here is a fact most people miss: in fiscal year 2024, more than 14,000 audits resulted in refunds for taxpayers. An audit is not a guilty verdict — it is a request to prove what you already claimed.

Audit risk lives in three buckets

When I think about audit risk, I put it into three buckets: your numbers, your patterns, and your proof. Most dentists worry about bucket one and ignore buckets two and three — which is exactly where audits are won or lost.

Bucket one: your numbers

Income level matters, but it is not the whole story. Very high income gets more attention because the potential recovery is larger. But very low reported income can also attract scrutiny when it does not match the economic activity — like a practice with heavy revenue but consistent losses, or large deductions that wipe out taxable income.

1. 01High deduction-to-income ratio. If your return shows $150,000 of income and every personal expense somehow became a business write-off, that stands out.
2. 02Repeated large losses. Schedule C losses, big depreciation write-offs, or real estate losses that offset W-2 and 1099 income get attention — especially if they are a recurring theme.
3. 03Too many round numbers. Exactly $3,000 in meals or $5,000 in supplies looks estimated, not documented.

Bucket two: your patterns

This is where most IRS notices begin. The IRS receives copies of your W-2s, 1099s, K-1s, and other information returns. If your return does not match what they already have, the system flags it automatically. That is not deep investigation — that is data matching, and it is one of the fastest ways to create an IRS issue.

1. 01Under-reported income. Leaving off a 1099 or K-1 income item is a direct mismatch.
2. 02Math errors and filing mistakes. The IRS sent over 1.7 million math error notices in fiscal year 2024. Wrong boxes, wrong carryovers, and missing forms create friction.
3. 03Schedule C filing. Sole proprietors and independent contractors face more scrutiny than S corps, C corps, or partnerships because that is where the IRS sees inflated expenses, missing mileage logs, and mixed personal spending.
4. 04Cash-heavy activity and late filing. Both increase risk profile without proving anything is wrong.

Bucket three: your proof

This is where most people lose audits — not because the strategy was illegal, but because they could not prove it. In a tax audit, the burden of proof is on you, the taxpayer. A bank statement shows money was spent, but it does not show why it was business-related or whether it meets the rules for that deduction.

• Receipts, not just statements.
• Business purpose noted at the time of the expense.
• Mileage logs where required.
• Documentation created when the expense happened, not two years later from memory.

Myths that need to die

• A home office deduction does not automatically trigger an audit.
• Having an LLC does not automatically protect you from an audit.
• Using tax strategies does not automatically trigger an audit.
• A large deduction does not automatically mean you did something wrong.

“What matters is whether the return is accurate, the numbers make sense, and you can support the position if the IRS asks.”

How to actually protect yourself

1. 01Report all income. Do not play games with W-2s and 1099s — the matching system will catch it.
2. 02Clean your books before the return is filed. Tax season is not the time to guess.
3. 03Do not write things off because someone on TikTok called it a loophole. A write-off is not a strategy if it falls apart when someone asks for proof.
4. 04Keep documentation in real time. Capture the receipt, the business purpose, and the context while it is still fresh.
5. 05Separate business and personal spending. One account and one card for everything creates sloppiness that is easy to challenge.
6. 06Work with a CPA who thinks beyond the return. Good tax planning asks: if the IRS asks about this later, what is our defense?