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# What is a Letter of Medical Necessity?

A Letter of Medical Necessity (LMN) is the document that makes an eligible purchase reimbursable from an FSA or HSA. It's a short note from a licensed clinician stating that the product or service supports the customer's health.

A licensed clinician in the Burst network reviews every request and issues the letter. Your customer answers a short health questionnaire; you never see their health answers. See [What customer information do I see in Leads?](/leads-privacy)

## Why it matters for your business

Many health and wellness products and services only qualify for FSA/HSA spending when they're paired with an LMN. With the letter, your customer pays with pre-tax dollars they've already set aside, which typically saves them 30 to 40% depending on their tax rate.

## What you don't have to do

* You don't write or sign anything.
* You don't make eligibility claims. Burst checks which of your offerings can be eligible. See [How Burst decides which offerings are eligible](/product-eligibility).
* You don't change your checkout. Customers pay normally and get reimbursed afterward.