IRS Audit Red Flags: What Triggers an Audit (and How to Avoid One)

Nobody wants an IRS audit notice in their mailbox. The good news? Your odds of being audited are actually pretty low—less than 1% for most taxpayers.

But certain things dramatically increase your risk.

The short answer: The IRS uses computer algorithms to flag returns that look unusual. High income, large deductions, missing income, and inconsistencies all raise red flags. Understanding these triggers helps you file confidently while avoiding unnecessary risk.

How the IRS Selects Returns for Audit

The IRS doesn't randomly pick returns to audit. They use three main methods:

1. Discriminant Information Function (DIF)

Every return gets a DIF score based on how unusual it looks compared to similar returns. High DIF scores get flagged for review.

What affects your DIF score:

Deductions that are unusually high for your income level
Income patterns that don't match your profession
Ratios that differ significantly from comparable taxpayers

2. Document Matching

The IRS receives copies of your W-2s, 1099s, K-1s, and other information returns. Their computers automatically match these against what you reported.

Mismatches trigger immediate notices. If your employer reported $80,000 in wages but you only reported $70,000, the computer catches it instantly.

3. Related Audits

If your business partner, investor, or related party is audited, you might be too. The IRS follows the money.

The Real Audit Rates

Not all returns face equal scrutiny:

Income Level	Audit Rate
Under $25,000	0.4%
$25,000 - $50,000	0.2%
$50,000 - $75,000	0.2%
$75,000 - $100,000	0.3%
$100,000 - $200,000	0.4%
$200,000 - $500,000	0.6%
$500,000 - $1M	1.0%
$1M - $5M	1.4%
$5M - $10M	2.0%
Over $10M	7.5%

Key insight: Higher income means higher scrutiny. But even at $1 million in income, your audit rate is only 1.4%.

Schedule C Filers Beware

Self-employed individuals with Schedule C income face higher audit rates than W-2 employees at similar income levels. The IRS knows self-employment offers more opportunities for underreporting.

Top Audit Red Flags

1. Not Reporting All Income

This is the #1 audit trigger. The IRS receives copies of every 1099 and W-2 sent to you. If you don't report that $500 freelance payment, the computer flags it automatically.

How to avoid it: Report every dollar of income. Even if you think a 1099 is wrong, report it and then explain the discrepancy.

2. Large Charitable Deductions

Charitable giving is great. But deductions that seem disproportionate to your income raise flags.

Red flag zone: Donating more than 3-5% of your income, especially non-cash donations.

How to protect yourself: Keep receipts for everything. For non-cash donations over $500, complete Form 8283. For donations over $5,000, get an appraisal.

3. High Business Deductions Relative to Income

A business that consistently shows losses, or one with expenses that seem too high for the revenue, draws scrutiny.

Red flag zone:

Schedule C losses year after year
Business expenses exceeding 50-60% of revenue
Home office deduction with minimal business income

How to protect yourself: Keep meticulous records. Be able to prove every deduction. Don't claim a "business" that's really a hobby.

4. Round Numbers Everywhere

Real expenses rarely come out to exactly $1,000 or $5,000. A return full of round numbers suggests estimation rather than actual record-keeping.

Red flag zone: Multiple deductions ending in zeros.

How to protect yourself: Report actual amounts. $4,847 looks more legitimate than $5,000—because it probably is.

5. Home Office Deduction

The home office deduction has historically been an audit magnet. It's not that claiming it is wrong—it's that many people claim it incorrectly.

Red flag zone:

Large home office relative to home size
Home office with minimal business income
Home office for W-2 employees (not allowed!)

How to protect yourself: Only claim if you have a dedicated space used exclusively for business. Take photos. Keep measurements.

6. Vehicle Deduction at 100%

Very few people use their vehicle 100% for business. Claiming full business use is a major red flag.

Red flag zone: 100% business use, especially for a vehicle that's your only car.

How to protect yourself: Keep a mileage log. Be realistic—most people with one vehicle are around 50-70% business use at best.

7. Cash-Intensive Businesses

Restaurants, bars, retail stores, and other cash businesses face extra scrutiny because cash is harder to trace.

Red flag zone: Cash businesses with unusually low reported income relative to industry norms.

How to protect yourself: Deposit all cash receipts. Keep detailed records. Report everything.

8. Excessive Business Meals

The meals and entertainment deduction is legitimate—but it's also frequently abused.

Red flag zone: Business meals that seem excessive for your business type or size.

How to protect yourself: Document the business purpose. Keep receipts. Note who you met with and what was discussed.

Special Audit Triggers

Cryptocurrency

The IRS has made crypto enforcement a priority. If you have cryptocurrency transactions:

Report all sales, even if at a loss
Answer the crypto question on your return honestly
Track your cost basis carefully

Foreign Accounts

Failing to report foreign accounts (FBAR) or foreign assets (FATCA) triggers serious penalties—and high audit risk.

Large Refunds

A refund that seems disproportionately large for your income level may trigger review. This is particularly true for refundable credits like the Earned Income Credit.

What Actually Happens in an Audit

If you're selected, don't panic. Most audits are "correspondence audits"—the IRS sends a letter asking for documentation on specific items.

Types of Audits

Type	What Happens	How Long
Correspondence	IRS mails questions; you mail answers	3-6 months
Office Audit	You visit an IRS office with documents	1 day + follow-up
Field Audit	IRS agent visits your home/business	Several days/weeks

Your Rights

Right to professional representation
Right to know why you're being audited
Right to appeal any findings
Right to privacy and confidentiality

Common Outcomes

No change: You were right; they were wrong
Agreed change: You owe more; you accept it
Disagreed change: You owe more; you appeal
Refund: Rare, but sometimes they find they owe you

How to Protect Yourself

Before Filing

Report all income — The IRS already knows about it
Keep good records — If you can't prove it, don't deduct it
Be reasonable — Deductions should make sense for your situation
Use actual numbers — Avoid round numbers that suggest guessing
Double-check math — Errors invite scrutiny

After Filing

Keep records for at least 7 years — The IRS can audit up to 3 years back (6 for substantial errors)
Respond promptly to IRS notices — Ignoring them makes everything worse
Consider representation — CPAs and tax attorneys can handle audits for you

If You're Audited

Don't panic — Most audits are resolved with documentation
Read the notice carefully — Know exactly what they're questioning
Gather documentation — Receipts, statements, contracts
Consider professional help — Especially for field audits
Know your rights — You can appeal unfavorable decisions

When to Worry (and When Not To)

Don't Worry If...

You reported all income
You have documentation for your deductions
Your return makes sense for your situation
You didn't claim anything you can't prove

Maybe Worry If...

You forgot to report some income
You estimated deductions without records
You claimed personal expenses as business
You have a cash business with loose records

The Bottom Line

The best audit protection is a well-documented, honestly prepared tax return. Don't be afraid to take legitimate deductions—but be able to prove them if asked.

If you're concerned about audit risk or have received an IRS notice, let's talk. An experienced CPA can review your situation and help you respond appropriately.

Got an IRS notice? Don't wait. Talk to me →

— Krystal Le, CPA

LeCPA helps individuals and businesses across Plano, Richardson, Frisco, and Dallas with tax preparation and IRS representation.