Have you ever tried to use your Flexible Spending Account (FSA) for a health-related expense and been told you needed a formal “Letter of Medical Necessity” for it to qualify? Although that sounds a little intimidating, it’s actually a straightforward document that can unlock FSA eligibility for a wide range of treatments and products your account might not otherwise cover.
Here’s what you need to know.
What Is an LMN?
A Letter of Medical Necessity (LMN) is a written statement from a licensed healthcare provider (typically your doctor, nurse practitioner, or specialist) explaining that a specific treatment, product, or service is medically necessary for the diagnosis, treatment, or prevention of a specific health condition.
Think of it as a bridge between your healthcare provider’s clinical judgment and your FSA administrator’s eligibility rules. The IRS sets the framework for what qualifies as a medical expense under Section 213(d) of the tax code, but many items and services fall into a gray area. An LMN is how you move something from “not clearly eligible” to “approved.”
Why Does It Matter?
FSAs are funded with pre-tax dollars, which means every dollar you spend through your account is essentially a tax-free dollar. That financial benefit comes with rules. The IRS requires that FSA expenses be used for qualified medical expenses. Items that are considered general health or wellness products (even if they genuinely help you feel better) don’t automatically qualify.
That’s where the LMN becomes important. Without one, expenses like these are typically ineligible for FSA reimbursement:
- Special dietary foods (gluten-free products for someone with celiac disease, for example)
- Exercise equipment (such as when prescribed for a specific health condition like heart disease)
- Air purifiers or humidifiers (when neededfor a diagnosed respiratory condition)
- Compression socks or sleeves (beyond standard over-the-counter versions)
- Massage therapy (such as for a diagnosed musculoskeletal condition)
- Wigs (for patients experiencing medically-caused hair loss)
With a valid LMN from your provider on file, these expenses can shift from ineligible to reimbursable. That can add up to meaningful savings over the course of a plan year.
What Must a Letter of Medical Necessity Include?
Not all letters are created equal. A vague note saying “this patient needs to eat better and avoid gluten” isn’t going to cut it. To be accepted by your FSA administrator, a proper Letter of Medical Necessity generally needs to include the following elements:
- Patient information. The full name of the FSA account holder (or eligible dependent) being treated.
- Provider information. The healthcare provider’s full name, credentials (MD, DO, NP, etc.), practice name, address, and contact information.
- Diagnosis or medical condition. A clear description of the specific medical condition being treated or managed. Referencing the relevant ICD-10 diagnosis code strengthens the letter considerably.
- Description of the recommended item or service. Exactly what is being recommended? “Air purifier” is less effective than “HEPA air purifier for use in the patient’s bedroom to reduce allergen exposure.”
- Medical justification. The provider should explain why the item or service is medically necessary for this specific patient and condition, not just that it might be helpful in general.
- Duration of need. How long will the patient require this item or service? Is it ongoing? For the calendar year? For a specific treatment period? This helps determine whether the LMN needs to be renewed.
- Provider signature and date. The letter must be signed and dated by the licensed provider. Unsigned or undated letters will be rejected.
Things to Keep in Mind
An LMN doesn’t guarantee reimbursement. It supports a claim, but your FSA administrator still determines final eligibility in accordance with IRS guidelines. When in doubt, reach out to your benefits administrator before making a purchase. Many administrators, including our team, are happy to review whether a particular expense is likely to qualify.
Also, LMNs typically need to be renewed annually. A letter from three years ago probably won’t satisfy a current-year claim, even for a chronic condition.
Finally, keep copies of everything, including the LMN, the receipt, and any related correspondence. Good recordkeeping is your best protection if questions arise.
A Powerful Tool
A Letter of Medical Necessity isn’t red tape for its own sake. It exists to ensure that pre-tax FSA dollars are used appropriately – and it’s actually a powerful tool that lets you use those dollars for a broader range of genuine medical needs.
If your healthcare provider has recommended something that you think should be covered by your FSA, it’s worth asking them for an LMN. Your wallet will thank you!
Beneliance serves employers and employees with first-rate benefits administration for FSA, HSA, COBRA, and other employer-sponsored benefits.
