Medical Necessity Letter Template: LMN Samples for PT, Speech and Behavioral Health

What is a letter of medical necessity? A letter of medical necessity (LMN) is a treating clinician's signed statement about a specific patient and a specific service that explains, against the payer's coverage criteria, why the service is needed and where the medical record proves it.

Undeny's Take

An LMN is a map of the chart, not a substitute for it. CMS says it bluntly for equipment: no order or "physician attestation by itself provides sufficient documentation of medical necessity," and commercial reviewers read letters the same way. The letters that get approved are almost dull: they quote the plan's criterion, then point to the page of the record that meets it. The ones that fail spend three paragraphs on the diagnosis and never say why a therapist, rather than a home program, has to deliver the care. Medicare's therapy manual is explicit that diagnosis or prognosis "cannot be the sole factor." Timing matters as much as content. Send the LMN with the authorization or concurrent review request, before the last approved visit, not after a CO-50 lands. Once a claim is denied you are writing an appeal, and the LMN becomes one exhibit inside it.

Pre-Service LMN or Post-Denial Appeal

The two documents are often confused, and sending the wrong one wastes a review cycle.

	Letter of medical necessity	Appeal letter after a denial
When	Before or during care: prior authorization, concurrent review, a request for more visits	After a claim or authorization is denied
Signed by	The treating clinician	The practice or billing team, often with the clinician's statement attached
Argues	This patient meets the coverage criteria for this service	The payer's decision was wrong, and here is the proof
Clock	The payer's decision timeframe	The payer's appeal deadline
Where it lives	The authorization request and the chart	The appeal packet, with the LMN as an exhibit

For a denial on a claim already paid or processed, use our insurance appeal letter template, which has a ready sample for a CO-50 medical necessity denial.

How fast a pre-service request should be decided

• Employer group health plans under ERISA: the Department of Labor claims rule requires a pre-service decision "not later than 15 days after receipt of the claim by the plan," with one extension of up to 15 days, and urgent care decisions within 72 hours. A request to extend an urgent course of treatment must be decided within 24 hours if it is made "at least 24 hours prior to the expiration of the prescribed period of time or number of treatments."
• Medicare Advantage, Medicaid and CHIP: under CMS-0057-F, these payers must send prior authorization decisions "within 72 hours for expedited (i.e., urgent) requests and seven calendar days for standard (i.e., non-urgent) requests," and beginning in 2026 must give a specific reason for any denial.

If the pre-service request is denied

The next step is a pre-service appeal, and its rules differ from a claim appeal. UnitedHealthcare warns that "you may be required to provide authorization and/or patient consent when completing a pre-service appeal." In Medicare Advantage, "A physician who is providing treatment to an enrollee may, upon providing notice to the enrollee, request a standard reconsideration of a pre-service request" on the enrollee's behalf. The regulation names a physician, so confirm with the plan who may file when the request is for therapy. For a missed authorization discovered after the visit, see CO-197.

When a Payer Expects an LMN

Prior authorization and concurrent review

Whenever a plan gates a service behind authorization, the LMN is the clinical narrative attached to the request. For behavioral health and other ongoing care, the same letter, updated with new measures, supports each concurrent review.

Continued therapy beyond a visit limit

Commercial plans often cap therapy visits, and a request for more visits needs a fresh LMN. Check first whether the limit is a coverage decision or an exclusion. ASHA's guidance is that if "the denial is related to a plan exclusion, the appeals process would not apply," so no letter can buy visits the contract excludes. ASHA publishes an appeal template titled "Continuation of medically necessary care beyond visit limitations."

Medicare outpatient therapy above the KX threshold

Congress repealed the Medicare therapy caps in 2018, and Original Medicare has no LMN form for therapy. Instead, CMS states that "Claims for services over the KX modifier threshold amounts without the KX modifier are denied," and for CY 2026 the threshold is "$2,480 for PT and SLP services combined, and $2,480 for OT services," with targeted medical review possible at $3,000. The justification lives in the record: Medicare's therapy manual says narratives that justify medical necessity are "encouraged but not required," and "A separate justification statement may be included" for care "more extensive than is typical for the condition treated." That statement is, in practice, an LMN filed in the chart. See modifier KX.

Durable medical equipment

For Medicare, the old certificate of medical necessity is gone: for dates of service on or after January 1, 2023, CMS says "providers and suppliers no longer need to submit CMNs or DIFs with claims," and claims sent with them attached are rejected and returned. What remains is a standard written order with the beneficiary name or MBI, a description of the item, quantity if applicable, order date, the treating practitioner's name or NPI, and signature, backed by chart notes. Commercial plans set their own DME forms and may still ask for a letter.

The Standard Your Letter Is Measured Against

Write to the payer's definition, not to the reviewer's sympathy.

• Original Medicare excludes services "not reasonable and necessary ... For the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member." CMS's Program Integrity Manual adds that a covered service is "Safe and effective," not experimental, and appropriate in duration and frequency, including being "One that meets, but does not exceed, the patient's medical need" and "At least as beneficial as an existing and available medically appropriate alternative."
• Medicare Advantage plans must base medical necessity decisions on "The enrollee's medical history (for example, diagnoses, conditions, functional status), physician recommendations, and clinical notes." Where a plan uses its own internal criteria, federal rules require them to be publicly accessible, so find and quote them.
• Commercial plans use their own definitions. HealthCare.gov's glossary defines medically necessary as "Health care services or supplies needed to diagnose or treat an illness, injury, condition, disease or its symptoms and that meet accepted standards of medicine," but ASHA notes the definition "can vary from payer to payer." Quote the member's plan.
• Mental health and substance use benefits in group health plans carry a disclosure right: the criteria for medical necessity determinations "must be made available ... to any current or potential participant, beneficiary, or contracting provider upon request." Ask for them before you write.

What reviewers check, and where the answer comes from

Element of the letter	What the reviewer is testing	Where it comes from in the chart
Diagnosis and onset	Is there a covered condition?	Evaluation, referral, ICD-10 codes on the plan of care
Functional limitation	Does it impair something that matters?	Objective measures and standardized tests
Need for skilled care	Could an unskilled person or home program do this?	Clinical reasoning in evaluation and progress notes
Plan, frequency and duration	Is the amount reasonable for this condition?	Plan of care
Measurable goals and progress	Is the care working, or maintaining function?	Progress reports and re-evaluations
Alternatives considered	Is this the least intensive effective option?	History of prior treatment and its results

Writing the LMN Step by Step

1. Pull the payer's policy or level-of-care criteria for the exact service and note each criterion you must meet.
2. Gather the evaluation, current plan of care, the latest progress report and any standardized measures with dates.
3. State the request in the first paragraph: the service, the CPT code, the frequency, the duration and the date range.
4. Describe the diagnosis and the functional limitation in measurable terms, with the test name, score and date.
5. Explain why the care requires a licensed clinician, naming the clinical judgment involved, and why a lower level of care or a home program alone is not enough.
6. Match each of the payer's criteria to a sentence in the letter and a page in the record, then list measurable goals and the expected discharge point.
7. Have the treating clinician review, sign and date the letter, file a copy in the chart, and submit it with the authorization or review request.

Full Letter of Medical Necessity Template

Use this as the base for any discipline. Replace every bracketed field and delete optional paragraphs that do not apply.

[Practice Name]
[Street Address], [City], [State] [ZIP]
Phone: [Phone] · Fax: [Fax] · NPI: [Group NPI]

[Date]

[Payer Name]
Attn: [Utilization Management or Prior Authorization Department]
[Fax Number or Portal Reference]

RE: Letter of medical necessity for [Service Description]
Patient: [Patient Name] · Date of birth: [Date of Birth]
Member ID: [Member ID] · Group number: [Group Number]
Requested service: CPT [CPT Code], [Frequency] for [Duration], [Start Date] to [End Date]
Diagnosis: [Diagnosis Description] ([ICD-10 Code]) · Onset: [Onset Date]
Authorization or case reference: [Reference Number, if any]

To the reviewer:

I am the treating [Discipline and Credentials] for [Patient Name], and I am requesting [authorization / continued authorization / additional visits] for [Service Description] as described above. This letter explains why the service is medically necessary under [Payer Name]'s [Policy Name and Number or Level-of-Care Guideline].

Clinical history. [Patient Name] has [Diagnosis], with onset on [Onset Date] following [event or course]. Prior treatment has included [prior treatment and dates], with [result].

Current status and functional limitation. On [Assessment Date], [Patient Name] scored [Score] on [Standardized Test or Measure] ([interpretation]). This limits [specific daily function, work, school or safety activity], for example [concrete example from the record].

Why skilled care is required. The plan requires [clinical judgment or technique] that only a licensed [Discipline] can provide safely, including [specific skilled elements]. A home program alone is not sufficient because [reason documented in the record].

Plan and goals. The plan of care dated [Plan Date] calls for [Frequency] for [Duration]. Goals: (1) [Measurable Goal 1] by [Date]; (2) [Measurable Goal 2] by [Date]. [Patient Name] will be discharged to [home program / lower level of care] when [discharge criterion].

Progress to date. [If continuing care: Since [Start Date], [Patient Name] has improved from [Baseline Measure] to [Current Measure]. / If maintenance care: Without skilled care, [Patient Name] is expected to [decline described in the record], and the services are needed to [maintain function / prevent or slow deterioration].]

Criteria met. [Policy Name] covers this service when [criterion]. The enclosed [document] at page [Page Number] documents [matching finding]. [Repeat for each criterion.]

Please contact me at [Phone] or [Email] with any questions or to schedule a peer-to-peer discussion.

Sincerely,

[Signature]
[Clinician Name], [Credentials]
NPI: [Rendering NPI] · License: [License Number and State]

Enclosures: [evaluation dated [Date]]; [plan of care dated [Date]]; [progress report dated [Date]]; [test or measure results].

Therapy LMN Samples: PT, Speech and Behavioral Health

Each sample replaces the body of the full template; keep its header, RE block and signature block.

Sample A: Letter of medical necessity for physical therapy beyond a visit limit

For Medicare patients, coverage "does not turn on the presence or absence of a beneficiary's potential for improvement from the therapy, but rather on the beneficiary's need for skilled care," a rule CMS restated in the Jimmo settlement for outpatient therapy. Medicare plans of care must state diagnoses, long-term goals, and the "Type, amount, duration and frequency of therapy services," recertification is due at least every 90 days, and progress reports at least "once every 10 treatment days." Commercial plans write their own rehabilitation criteria, so quote the plan's policy, not Medicare's, when the patient is commercially insured. APTA lists phrases that weaken notes, such as "Patient or client tolerated treatment well" and "Continue per plan"; keep them out of the letter too.

RE: Request for [Number] additional physical therapy visits
Patient: [Patient Name] · Member ID: [Member ID]
Diagnosis: [Diagnosis Description] ([ICD-10 Code]) · Visits used: [Visits Used] of [Visits Allowed] for [Benefit Year]

I am requesting [Number] additional physical therapy visits, [Frequency] for [Duration], for [Patient Name], who has used [Visits Used] of the [Visits Allowed] visits in the plan's [Benefit Year] benefit.

[Patient Name] began care on [Start Date] for [Diagnosis] after [event, for example surgery on [Surgery Date]]. At evaluation, [he / she / they] scored [Baseline Score] on [Outcome Measure] and could [baseline function, for example walk [Distance] with [Assistive Device]]. As of [Reassessment Date], the score is [Current Score] and [current function]. The remaining deficits are [specific impairments], which still prevent [specific activity, for example returning to work as a [Job Duties] or climbing [Number] stairs at home].

The remaining care requires a physical therapist because [clinical reasons: progression of loading after [Procedure], gait training with [Device] and fall risk documented by [Balance Measure and Score], manual techniques that cannot be self-administered]. The home exercise program is in place and is being progressed, but it does not address [specific deficit] without skilled supervision.

Goals for the requested visits: (1) [Measurable Goal 1] by [Date]; (2) [Measurable Goal 2] by [Date]. I expect to discharge [Patient Name] to an independent home program on or about [Expected Discharge Date].

[Optional, maintenance care: [Patient Name]'s condition is [progressive or chronic condition]. The goal of the requested visits is to [maintain current function / prevent or slow decline], and the program requires a therapist because [special complications or complexity documented in the record].]

Sample B: Speech therapy letter of medical necessity

ASHA's documentation list for establishing medical necessity is a ready checklist: medical history, the diagnosis, date of onset, physician referral "If required," the initial evaluation and date, the plan of treatment, and progress notes. ASHA also advises: "Refer to the health plan's definition of medical necessity, and provide evidence supporting why the requested care fits within that definition." Where a plan labels pediatric speech services educational or developmental, ASHA offers an "Educational versus restorative services" template; the letter's job is to show the medical basis of the disorder. See CPT 92507 for the individual speech and language treatment code.

RE: Letter of medical necessity for speech-language pathology services
Patient: [Patient Name] · Member ID: [Member ID]
Requested service: CPT [CPT Code], [Frequency] for [Duration]
Diagnosis: [Diagnosis Description] ([ICD-10 Code]) · Onset: [Onset Date]

I am requesting authorization for speech-language pathology treatment, [Frequency] for [Duration], for [Patient Name], who has [Diagnosis].

[Patient Name] was evaluated on [Evaluation Date]. On [Standardized Assessment Name], [he / she / they] scored [Score] ([Percentile or Severity Rating]). [Add instrumental or clinical findings, for example [Swallow Study Type] on [Date] showing [finding].] These results mean [Patient Name] cannot [functional limitation, for example make basic needs known, safely swallow [Consistency], or be understood by unfamiliar listeners [Percent Intelligibility] of the time].

The disorder has a medical basis: [link to the underlying condition documented in the record, for example a neurological event, structural condition or diagnosed disorder]. Treatment requires a speech-language pathologist because [skilled elements, for example selecting and adjusting compensatory strategies, motor speech techniques, or swallowing safety training that requires ongoing clinical judgment].

Goals: (1) [Measurable Goal 1] by [Date]; (2) [Measurable Goal 2] by [Date]. Caregivers are being trained to carry over [skills] at home, and discharge is planned when [discharge criterion].

[Optional, pediatric: Services are being requested to treat a medical condition, not for academic instruction. [If the child also receives school-based services: Those services address [educational goals]; the requested clinical treatment addresses [medical goals], as documented in the plan of care.]]

Sample C: Behavioral health letter of medical necessity

Ask the plan for its medical necessity criteria first; federal parity rules require group health plans to provide them to a contracting provider on request. Then build the letter from the record without exposing psychotherapy notes. HIPAA requires "an authorization for any use or disclosure of psychotherapy notes," and a covered entity "may not condition the provision to an individual of treatment, payment, enrollment in the health plan, or eligibility for benefits on the provision of an authorization," with narrow exceptions. CMS's Program Integrity Manual lists what falls outside psychotherapy notes, including "counseling session start and stop times, the modalities and frequencies of administered treatment, results of clinical tests," and any summary of diagnosis, functional status, treatment plan, symptoms, prognosis and progress. That list is exactly what belongs in the letter. See CPT 90837 for the 60-minute psychotherapy code.

RE: Request for continued authorization of outpatient psychotherapy
Patient: [Patient Name] · Member ID: [Member ID]
Requested service: CPT [CPT Code], [Frequency] for [Duration], [Start Date] to [End Date]
Diagnosis: [Diagnosis Description] ([ICD-10 Code]) · Level-of-care criteria applied: [Plan Guideline Name and Version]

I am requesting continued authorization of outpatient psychotherapy for [Patient Name], [Frequency] for [Duration], under [Plan Guideline Name].

[Patient Name] began treatment on [Start Date] for [Diagnosis]. At intake, [he / she / they] scored [Baseline Score] on [Measure Name, for example a standardized depression or anxiety scale]; on [Most Recent Date] the score was [Current Score]. Current symptoms include [symptoms in clinical terms], which impair [functional areas, for example work attendance, school performance, self-care or relationships], as shown by [specific documented examples].

Treatment uses [modality, for example a named evidence-based therapy], with [Number] sessions completed. Progress includes [measurable change]. Remaining treatment targets are [targets]. [If relevant: Risk assessment on [Date] showed [summary documented in the record], which [supports / is managed by] the current frequency.]

The current frequency is the least intensive level that is clinically appropriate because [reason, for example symptoms worsened during [period] when sessions were reduced to [Frequency], as documented on [Date]]. A higher level of care is not indicated because [reason]. Treatment will step down to [Lower Frequency] when [criterion], with discharge planned when [discharge criterion].

[Optional: Please provide the medical necessity criteria used for this review, as available to contracting providers under federal parity rules.]

The Chart Has to Back Every Sentence

A letter cannot create documentation that does not exist. CMS's equipment rule makes the principle explicit: "There must be information in the patient's medical record that supports the medical necessity for the item." For therapy, Medicare reviewers "shall consider the entire record," so the letter, the plan of care and the notes must tell the same story with the same numbers.

• Match every number. Scores, dates and visit counts in the LMN should appear in the notes exactly as written.
• Do not backfill. CMS expects services to be "documented in the medical record at the time they are rendered," and any amendment or delayed entry must show its date and author.
• Show skill, not attendance. APTA's top payer complaints include notes that do "not demonstrate skilled care" and "Repetitious daily notes showing no change in patient status."
• File the letter. Keep the signed LMN in the chart so it can be produced in an audit or attached to a later appeal.

Frequently Asked Questions

Who should sign a letter of medical necessity?

The treating clinician who evaluated the patient and wrote the plan should sign it, such as the therapist for a therapy request or the treating practitioner for equipment. Billing staff can prepare the draft, but the clinical statements must be the clinician's own. Medicare therapy plans of care also require certification by a physician or nonphysician practitioner, a separate step from the letter.

Is a letter of medical necessity the same as a prior authorization?

No. Prior authorization is the payer's approval process, and the letter of medical necessity is one document you submit within it. Some authorization requests are approved on the evaluation and plan of care alone, while a complex or extended request usually benefits from a letter that ties the record to the plan's criteria.

Does Medicare require a letter of medical necessity for therapy above the KX threshold?

No form or letter is required. Above the annual threshold, which CMS set at $2,480 for PT and SLP combined and $2,480 for OT in 2026, claims need the KX modifier, and the record must justify the care. Medicare's therapy manual encourages a narrative or separate justification statement when care is more extensive than typical.

Is a certificate of medical necessity still required for Medicare DME?

No. CMS ended certificates of medical necessity and DME information forms for claims with dates of service on or after January 1, 2023, and claims sent with them attached are rejected. Medicare now relies on the standard written order plus medical record documentation.

Can I send psychotherapy notes with a behavioral health letter of medical necessity?

You should not need to. HIPAA requires the patient's authorization to disclose psychotherapy notes, and a covered entity cannot condition payment on that authorization except in narrow cases. Summaries of diagnosis, symptoms, functional status, test results, treatment plan and progress are not psychotherapy notes, and those are what the letter should contain.

Can a letter of medical necessity be written after the service?

Yes, as an exhibit in an appeal, but it must summarize documentation that already existed on the date of service. CMS expects services to be documented when rendered, and any late entry must be clearly dated and attributed. A letter that adds facts missing from the notes will not cure the gap.

How long should a letter of medical necessity be?

One to two pages is usually enough. Lead with the request, give the measurable findings, explain why skilled care is needed, and match each payer criterion to a page in the attached record.

Informational only, not legal, medical, or billing advice. Verify against current payer policy, the member's plan and your licensing rules before submitting.

Denied Anyway? Turn the LMN Into an Appeal

Undeny drafts the appeal letter from the denial code and payer, so the medical necessity case you already built goes straight into the packet. Generate an appeal · See the appeal letter template · Join the waitlist