By Yegor Nadvornyy, Founder of Brainrich Kids · Updated July 2026 · 11-minute read
TL;DR
A Letter of Medical Necessity (LMN) is a signed statement from a licensed provider that connects sensory equipment to your child's diagnosed condition. A valid one needs six elements: patient details, the diagnosis, the specific item, how it treats the condition, treatment duration, and the provider's signature with credentials. It's generally valid for 12 months. This guide includes a copy-paste template your provider can adapt, plus the exact language that passes administrator review — and the language that gets denied.
Here's a number that surprises most parents: an FSA administrator can deny a claim over a missing date next to a signature.
The Letter of Medical Necessity is the single document standing between you and roughly 30% savings on sensory equipment. Get it right and reimbursement is a formality. Get one element wrong and you're re-filing paperwork for weeks.
This guide covers what the letter must say, who can write it, a template you can hand your provider today, and the two ways to get one — including the 5-minute route built into our checkout.
What a Letter of Medical Necessity Actually Does
HSA and FSA rules split expenses into three buckets:
- Always eligible: prescriptions, doctor visits, crutches. No extra paperwork.
- Never eligible: expenses that are "merely beneficial to general health," per IRS Publication 502.
- Dual purpose: items that serve both wellness and treatment — exercise equipment, sensory tools, climbing gyms. Eligible only with documentation tying them to a diagnosed condition.
Sensory equipment sits in that third bucket. The LMN is the document that moves it from "not eligible" to "eligible" — for your child specifically, based on a licensed provider's judgment.
One clarification parents often miss: an LMN is not a prescription. It doesn't need a prescription pad or a pharmacy. It's a signed letter, and administrators accept standard letterhead or their own LMN forms.
Who Can Write One
More provider types can write LMNs than most families realize:
| Provider | Typical fit for sensory equipment | Notes |
|---|---|---|
| Pediatrician (MD/DO) | Strong — knows the full medical history | Accepted by essentially all administrators |
| Occupational therapist (OT) | Strongest clinical rationale — sensory integration is OT territory | Acceptance is plan-specific; some plans want a physician co-signature |
| Physical therapist (PT) | Strong for gross-motor and strength goals | Same plan-specific caveat as OT |
| Nurse practitioner / physician assistant | Strong | Widely accepted |
| Licensed psychologist / psychiatrist | Fit for ADHD and regulation-focused goals | Useful when the diagnosis is behavioral |
Two rules of thumb keep you safe:
- Use a treating provider. Some administrators require that the signer has treated your child for the named condition within the past six months.
- When in doubt, ask your administrator first. One email — "do you accept LMNs signed by a licensed OT?" — saves a denied claim later.
The Six Elements Every LMN Needs
We compiled this from the published LMN forms of major administrators, including FSAFEDS, ASIFlex, and HealthEquity. Their formats differ. Their required content doesn't:
| # | Element | Why administrators check it |
|---|---|---|
| 1 | Patient name and date of birth | Matches the claim to the dependent |
| 2 | Specific diagnosis, with history and duration | Proves this treats a condition, not general wellness |
| 3 | The specific item or service recommended | Ties the receipt to the letter; vague items get flagged |
| 4 | How the item treats or mitigates the condition | The clinical logic — the heart of the letter |
| 5 | Duration of recommended treatment | Sets the validity window, usually 12 months |
| 6 | Provider name, credentials, license, signature, date | Unsigned or undated letters are rejected outright |
Some administrators also ask for a product code or the provider's NPI number. Check your plan's LMN form — if they publish one, use theirs.
The Template
Hand this to your child's provider as a starting point. They'll adapt it to your child's actual evaluation — the clinical content must reflect their professional judgment, not a script. Bracketed fields are placeholders.
[Provider letterhead]
Date: [date — must be on or before the purchase date]
RE: Letter of Medical Necessity for [child's full name], DOB [date of birth]
To whom it may concern:
I am a licensed [credential — e.g., occupational therapist, license #____] and have treated [child's first name] since [month/year] for [specific diagnosis — e.g., sensory processing disorder / autism spectrum disorder / ADHD / hypotonia]. [One to two sentences of history: when diagnosed, current symptoms, functional impact — e.g., difficulty with self-regulation, delayed gross-motor milestones, sensory-seeking behavior.]
As part of [child's first name]'s treatment plan, I recommend the daily home use of an indoor climbing and sensory gym (specifically: [product name, e.g., Brainrich Spider V3 indoor play gym]). This equipment is medically necessary to [clinical rationale — e.g., provide daily proprioceptive and vestibular input, build core and upper-body strength per the home exercise program, support self-regulation between therapy sessions]. This recommendation treats the diagnosed condition above and is not for general health or recreation.
The recommended duration of this treatment is [duration, e.g., 12 months], after which I will re-evaluate.
Please contact my office with any questions.
Sincerely,
[Provider signature]
[Printed name, credentials]
[License number / NPI]
[Practice name, phone]
This template is educational. Only a licensed provider who treats your child can decide whether the equipment is medically necessary, and the wording must reflect their evaluation. Your plan administrator makes the final eligibility call.
Language That Passes vs. Language That Fails
In March 2024, the IRS warned that letters based on general wellness claims don't make an expense medical. The recommendation must be diagnosis-specific and treatment-targeted. Here's the difference in practice:
| Fails review | Passes review |
|---|---|
| "Exercise equipment would benefit this child's health and fitness." | "Daily climbing provides the proprioceptive input required by his sensory processing disorder treatment plan." |
| "Active play is important for all children." | "She requires structured vestibular activity 5+ days per week to address regulation deficits documented in her OT evaluation of March 2026." |
| "A play gym will keep him active indoors." | "Home equipment allows him to complete his prescribed strengthening program between weekly PT sessions for hypotonia." |
Notice the pattern. Passing language names the diagnosis, references the treatment plan, and states a frequency or goal. Failing language could describe any child on earth.
How to Ask Your Provider
If your child already sees an OT, PT, or pediatrician, the ask takes one conversation. A script that works:
"We're setting up home equipment to support [child]'s therapy goals between sessions — an indoor climbing and sensory gym. Our FSA can cover it with a letter of medical necessity. Could you write one? I have a template with the six elements our administrator needs."
Providers write these letters routinely. OTs in particular — sensory integration equipment is standard home-program territory. Bring the template above, your administrator's LMN form if they publish one, and the product page printout showing what the equipment is.
The Faster Route: An LMN at Checkout
No current provider, or no appointment until October? There's a second path. Brainrich checkout includes an integrated HSA/FSA option:
- Select HSA/FSA as your payment option at checkout.
- Answer a short health survey — 3 to 5 minutes.
- An independent licensed provider reviews your responses. Approval is case-by-case, not automatic.
- If approved, a signed LMN lands in your inbox. Pay with your HSA/FSA card, or save the letter and file for reimbursement.
The same six-element standard applies — the provider writes the letter, not you. Complete the survey on or before the day you purchase. Details on our funding page, and the full eligibility picture is in our complete HSA/FSA guide.
Validity, Renewal, and Timing Rules
- 12-month validity. The standard across administrators. New purchases after expiry need a renewed letter.
- Date before purchase. The LMN must be signed on or before the purchase date. A letter written after the fact is the most common denial we hear about.
- Keep three documents together: the LMN, the itemized receipt, and proof of payment. FSA users submit them with claims. HSA users hold them for IRS records — weak documentation at audit means back taxes plus a 20% penalty.
- One letter can cover a category of care. If the letter recommends "an indoor climbing and sensory gym plus related safety equipment," a crash mat purchased the same day fits under it. Ask your administrator how broadly they read the recommendation.
If the Claim Comes Back Denied
Don't assume the answer is final. Administrator denials usually cite fixable gaps:
| Denial reason | Fix |
|---|---|
| Missing signature, date, or credentials | Ask the provider to re-issue with all six elements; resubmit |
| "General wellness" language | Re-issue with diagnosis-specific, treatment-plan wording (see table above) |
| Receipt not itemized | Request an itemized invoice from the merchant — we email one on request at info@brainrichkids.com |
| Provider type not accepted | Get a co-signature from your pediatrician, or re-issue under an accepted credential |
| LMN dated after purchase | Hardest to fix — some plans allow appeal with records showing the treatment relationship predated purchase |
Every appeal goes further with the denial reason in writing. Ask for it — administrators must tell you why.
Beyond HSA/FSA: When a Waiver Pays Instead
An LMN unlocks pre-tax dollars — your own money, saved from taxes. For families of children with developmental disabilities, state Medicaid waiver programs can go further and fund equipment directly. Categories like "specialized medical equipment" and "assistive technology" exist in most states' waivers. We mapped all 50 states in our state-by-state waiver guide.
Frequently Asked Questions
Can an occupational therapist write a letter of medical necessity for sensory equipment?
In many plans, yes — and OTs often write the strongest clinical rationale for sensory equipment. Some administrators require a physician's signature, so confirm with your plan first.
Does a letter of medical necessity guarantee reimbursement?
No. Your plan administrator reviews every claim and holds final authority. A complete, diagnosis-specific letter makes approval far more likely, but no letter guarantees it.
How much does it cost to get an LMN?
Through your child's existing provider, often nothing beyond a normal visit. Third-party LMN services used by many merchants reportedly charge around $20–$30. Brainrich's checkout survey is built into the purchase flow.
How long does the LMN process take at Brainrich checkout?
The survey takes 3–5 minutes. Provider review is asynchronous — no appointment, no video call. The signed letter arrives by email if approved.
Can I write the letter myself and have my doctor sign it?
You can bring a template — that's what the one above is for. But the clinical content must reflect the provider's own evaluation and judgment. Administrators and the IRS treat rubber-stamped letters as invalid.
Do I need a new LMN for each purchase?
Not within the validity window. A letter recommending a category of equipment can cover related purchases for 12 months. New purchases after expiry need a renewal.
What diagnosis codes should the letter include?
A written diagnosis is required; some administrators also want the ICD-10 code and the provider's NPI. Your provider knows the codes. If the plan publishes its own LMN form, those fields are marked on it.
Skip the paperwork chase
The LMN process is built into our checkout — survey, provider review, signed letter by email. Start by finding the right gym for your space.
Take the 60-second quiz →About the author: Yegor Nadvornyy is the founder of Brainrich Kids, maker of steel tension-mounted indoor play gyms used in thousands of American homes, including many families running OT and PT home programs. This article is educational, not medical, tax, or legal advice. Sources: IRS Publication 502; IRS wellness-expense alert, March 2024; published LMN forms from FSAFEDS, ASIFlex, and HealthEquity.
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