Tax audits triggered by medical expense deductions are uncommon. Fewer than 0.4% of individual returns face any kind of IRS examination in a given year, and most of that scrutiny lands on high-income filers or obvious reporting errors rather than medical claims. The deduction itself has a high floor before it produces any tax benefit, which already thins out who claims it. A medical write-off can still draw attention when it looks unusually large next to your income, but for most people the odds of being reviewed specifically over medical expenses are slim.
The Baseline Audit Rate for Individuals
The IRS publishes audit statistics each year through its Data Book, and the numbers consistently show that the vast majority of returns are accepted as filed.1Internal Revenue Service. Compliance Presence In fiscal year 2024, the agency closed about 505,500 individual return audits out of the roughly 150 million filed.2Internal Revenue Service. IRS Data Book
Audit risk climbs steeply with income. For tax year 2019, taxpayers reporting $10 million or more in total positive income faced an 11% audit rate. Those between $5 million and $10 million saw 3.1%, and the $1 million to $5 million range came in at 1.6%.1Internal Revenue Service. Compliance Presence Below the million-dollar line, rates drop well under 1%. If your income is moderate and your return is straightforward, an audit of any kind is unlikely, and an audit centered on medical expenses is rarer still.
What Actually Puts a Medical Deduction on the IRS Radar
The IRS scores every return with a computer system called the Discriminant Function System, which compares your figures against statistical norms for taxpayers with similar income and filing characteristics.3Internal Revenue Service. FS-2006-10 – The Examination (Audit) Process Numbers that deviate sharply from expectations push the score up and make human review more likely.
For medical expenses, the usual trigger is size relative to income. Someone earning $60,000 who claims $25,000 in medical costs stands out far more than someone earning $300,000 with the same claim. The system also notices round numbers, since $10,000 flat looks estimated where $9,847 looks recorded. A sudden spike compared to prior years without an obvious explanation gets attention too. None of these signals guarantees an audit; they raise the chance that a reviewer takes a second look.
Why Few Taxpayers Even Claim the Deduction
Two structural rules keep the pool of medical-deduction claimants small, which is part of why audits focused on this line item are rare.
The first is the 7.5% floor. Federal law allows you to deduct only the portion of medical spending that exceeds 7.5% of your adjusted gross income.4Office of the Law Revision Counsel. 26 USC 213 – Medical, Dental, Etc., Expenses If your AGI is $100,000, the first $7,500 of medical spending produces no benefit at all. Spend $12,000 and only $4,500 counts. You generally need a year with major surgery, chronic illness, or other substantial care before the deduction starts working in your favor.
The second is itemization. Medical expenses only produce a benefit if you itemize on Schedule A instead of taking the standard deduction. For 2026, the standard deduction is $16,100 for single filers, $32,200 for joint filers, and $24,150 for heads of household.5Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Even a substantial medical figure can disappear if your total itemized deductions don’t beat that number. Between the floor and the standard deduction, most people never end up claiming a medical write-off at all.
The Mistakes That Draw Attention
Most medical-expense audits come down to a simple question: can you prove what you claimed, and did you correctly subtract reimbursements? Two categories of error account for most trouble.
The first is including expenses that don’t qualify. The IRS defines deductible medical care as spending for diagnosis, treatment, prevention of disease, or anything affecting a structure or function of the body.4Office of the Law Revision Counsel. 26 USC 213 – Medical, Dental, Etc., Expenses Doctor visits, surgery, hospital stays, dental and vision care, mental health treatment, prescription drugs, insulin, and health insurance premiums paid with after-tax dollars all qualify. Common misses: over-the-counter medications only count if a doctor prescribes them, gym memberships and general wellness programs are almost always disallowed, and cosmetic procedures don’t count unless they correct a deformity from illness, injury, or a congenital abnormality.
The second is failing to subtract reimbursements. You cannot deduct any expense paid by insurance or through a tax-advantaged account like an HSA, FSA, Archer MSA, or HRA.6Internal Revenue Service. Frequently Asked Questions About Medical Expenses Related to Nutrition, Wellness and General Health If you spent $15,000, insurance covered $8,000, and your HSA covered $3,000, only $4,000 belongs on Schedule A. This is a frequent audit trigger because the IRS can cross-reference Form 1099-SA and W-2 Box 12 codes against what you claimed.
Documentation That Protects You
If your return is selected, the IRS will want proof that each expense was real, medically necessary, and unreimbursed. Keep receipts, cancelled checks, bank statements, and insurance explanation-of-benefits forms. Each record should show who was paid, the date, the amount, and what service was provided.
For anything that isn’t obviously medical (a special mattress, home modifications, prescribed supplements), keep a written statement from your physician explaining the medical necessity and the condition being treated. Without that letter, the IRS will disallow the expense almost automatically.
If you claim medical mileage, maintain a contemporaneous log with the date, destination, purpose, and miles for each trip. The IRS won’t accept a year-end estimate. Digital records are fine as long as they’re complete, legible, and retrievable.
Keep everything for at least three years from the filing date, which is the standard window for the IRS to open an examination.7Internal Revenue Service. How Long Should I Keep Records The window stretches to six years if you significantly underreported income, so longer retention is sensible.
What an Audit Actually Looks Like
The IRS always initiates contact by mail, never by phone.8Internal Revenue Service. IRS Audits About 85% of individual examinations are correspondence audits, where the agency sends a letter asking you to mail in documentation for specific line items.9Congress.gov. Distribution of IRS Audits by Income and Race Medical expense reviews almost always fall into this category. The question is usually whether you can prove what you claimed.
You typically get 30 days to respond.10Taxpayer Advocate Service. Letter 525 Audit Report/Letter Giving Taxpayer 30 Days to Respond If your records back up the return, the IRS issues a no-change letter and closes the matter. If you don’t respond or can’t document the claim, the deduction gets disallowed and the agency assesses the additional tax plus interest.
Penalties and Your Right to Challenge
An overstated medical deduction results in the additional tax plus interest from the original filing deadline. If the IRS decides the understatement was substantial (at least 10% of the correct tax or $5,000, whichever is greater), a 20% accuracy-related penalty applies on top.11Internal Revenue Service. Accuracy-Related Penalty Honest mistakes with reasonable cause can sometimes avoid the penalty if you explain what happened.
If you disagree with the findings, the IRS issues a notice of deficiency. You have 90 days from the date on that notice to petition the U.S. Tax Court, or 150 days if you’re outside the country.12Internal Revenue Service. Understanding Your CP3219N Notice Missing that deadline forfeits the right to contest before paying, and that lapse is genuinely difficult to undo.
The practical defense is straightforward. Claim only what clearly qualifies, subtract every reimbursement, keep organized records, and avoid round numbers. Taxpayers who do those things rarely hear from the IRS about their medical deduction at all.