How to Fill Out and Submit an FSA Medical Necessity Form

An FSA letter of medical necessity is a one-page form your healthcare provider signs to confirm that a specific expense treats a diagnosed medical condition rather than serving general wellness. You need one whenever you file a Health Care FSA claim for a “dual-purpose” item, meaning something that could be either a personal purchase or a medical one depending on the circumstances. The form is a free PDF download from fsafeds.gov, and you submit it with your claim for reimbursement.¹

When You Need One

FSAFEDS sorts every product and service into three buckets: eligible with just a receipt, ineligible entirely, and conditionally eligible, which the program calls “Maybe Expenses.”² The middle category is where the letter of medical necessity comes in. If your provider believes a Maybe Expense, or even a normally ineligible expense, is medically necessary for you, the LMN is the document that opens the door to reimbursement.

The reason has to do with how the IRS defines qualifying medical care under Internal Revenue Code Section 213(d): amounts paid for the diagnosis, cure, mitigation, treatment, or prevention of disease, or for affecting any structure or function of the body.³ An expense only counts when it goes beyond general health maintenance; the test is whether you would have incurred the cost at all if not for a specific condition.⁴

Common expenses that require an LMN include:

Weight loss programs, when prescribed to treat a diagnosed disease such as obesity, hypertension, or heart disease. Gym memberships and diet food still don’t qualify, but structured program fees can.⁵
Vitamins and supplements, when a provider determines you have a specific deficiency or condition requiring supplementation beyond a normal diet.⁶
Massage therapy, when prescribed to treat a physical injury or diagnosed musculoskeletal condition rather than for relaxation.
Activity trackers and HEPA air purifiers, which require both an LMN and a detailed receipt.²
Alternative treatments such as acupuncture and chiropractic care that fall outside clearly eligible categories.²

One boundary worth knowing: cosmetic procedures. They’re specifically excluded from qualified medical expenses unless the procedure corrects a deformity caused by a congenital abnormality, an accident or trauma, or a disfiguring disease.⁷ Breast reconstruction after a cancer-related mastectomy qualifies. Teeth whitening for age-related discoloration does not.⁸ An LMN won’t override that exclusion.

What the Form Asks For

The FSAFEDS LMN is split into two sections: one you fill out and one your provider completes.¹

Your part is straightforward. You provide the patient’s name, which can be you, your spouse, or an eligible dependent.

Your licensed practitioner fills out the rest:

The specific medical condition that makes the expense necessary. A vague entry like “general wellness” will get the claim denied. The more precise the diagnosis, the smoother the review.
The duration of treatment. For chronic conditions such as multiple sclerosis, the form instructs providers to write “lifetime.” Once the stated duration expires, you’ll need a new LMN to keep getting reimbursed for that expense.¹
The practitioner’s printed name, signature, and date. No stamp, NPI number, or letterhead is required by the form itself, though adding them doesn’t hurt.

The form also carries a certification statement: the provider is confirming that the expense is medically necessary for the patient and is not for general health or cosmetic purposes. That distinction is the entire point of the document. If the explanation doesn’t clearly connect the specific diagnosis to the specific expense, the claims processor has no basis to approve it.

Who Can Sign It

The form uses the term “Licensed Practitioner” without listing specific professional titles.¹ In practice, physicians (MDs and DOs), nurse practitioners, and physician assistants are the safest signers. For mental health treatment, a licensed clinical psychologist or psychiatrist is the strongest choice. The FSAFEDS eligible expense list notes that alternative healers qualify for reimbursement “when rendered by a licensed, certified, and/or registered health care provider,” which suggests the same licensing standard applies to LMN signatures for those services.² If you’re uncertain about whether your provider’s credentials will be accepted, contact FSAFEDS before filing.

How to Submit It

You submit the completed LMN with your Health Care FSA claim form and a detailed receipt showing the service, who received it, and the amount charged. The LMN has to accompany each claim you file for that expense. It isn’t a one-time upload that covers future claims automatically.¹

Three channels are available:

Online: log in at fsafeds.gov and follow the claim submission steps to upload the LMN and supporting documents.⁹
Fax: 866-643-2245 (toll-free) or 650-577-5340.¹⁰
Mail: FSAFEDS Program – Claims, P.O. Box 14127, Lexington, KY 40512-4127.¹⁰

If you file without the LMN or other required documentation, processing stalls. FSAFEDS will reprocess the claim once the missing paperwork arrives, but your claim received date resets to the date they get the missing documents, and processing takes up to five business days from that revised date.⁹ Getting the LMN squared away before you file avoids that delay.

What Happens After You File

When a complete claim arrives, with receipt, claim form, and LMN together, FSAFEDS processes most claims within one to two business days. Payments follow shortly after by direct deposit.¹¹

Keep an eye on your online account after submitting. The dashboard shows claim status, and if something is denied, you’ll see the specific reason in your activity log. Catching a denial quickly leaves more time to fix the issue or file an appeal.

If Your Claim Is Denied

A denied claim has a structured appeal path with firm deadlines:

Informal review: contact an FSAFEDS Benefits Counselor within 30 calendar days of the decision for a detailed explanation of the denial.¹²
First-level written appeal: submit within 60 calendar days of the initial decision, including your reasons for disagreeing and any supporting documents such as a revised LMN, an Explanation of Benefits, medical records, or detailed bills.¹³
Second-level appeal: if the first is upheld, you have 30 more calendar days to file for reconsideration.¹²
Independent third-party review: if the second-level appeal is also upheld, you have another 30 calendar days to request review by an independent party.¹²

Most LMN-related denials come down to documentation problems: the diagnosis is too vague, the connection between the condition and the expense isn’t explained, or the LMN was missing altogether. When a provider rewrites the LMN with a clearer diagnosis and a more specific explanation of medical necessity, that alone can resolve a first-level appeal.

1
FSAFEDS. Letter of Medical Necessity Form
2
FSAFEDS. Eligible Health Care FSA (HC FSA) Expenses
3
Office of the Law Revision Counsel. 26 U.S. Code 213 – Medical, Dental, Etc., Expenses
4
Congressional Research Service. Health Savings Account (HSA) Qualified Medical Expenses
5
Internal Revenue Service. Publication 502 – Medical and Dental Expenses
6
Internal Revenue Service. Frequently Asked Questions About Medical Expenses Related to Nutrition, Wellness and General Health
7
Office of the Law Revision Counsel. 26 USC 213
8
Internal Revenue Service. Revenue Ruling 2003-57
9
FSAFEDS. Submitting Claims Quick Reference Guide
10
FSAFEDS. Need Help?
11
FSAFEDS. FAQs
12
FSAFEDS. File an Appeal
13
FSAFEDS. How Do I Appeal a Claim That Has Been Denied?