Medical necessity documentation is the part of the record that shows a payer why this patient needed this service, at this frequency, on this date. In behavioral health it lives mostly in the progress note and the treatment plan. A note can describe a good session and still fail the test. It fails when it never ties the work to a diagnosis, a functional problem and a reason to keep going.
This guide uses two primary sources: the CMS fact sheet on medical record documentation and the Medicare coverage policy for psychiatric services. It lists what each one asks for, how to write it into a note, and three sample notes you can compare against your own.
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START FREE TRIAL →What is medical necessity documentation?
It is the evidence, written in the chart, that a service was reasonable and necessary for the patient's condition. Payers do not take that on trust. They read the record, and if the record does not show it, the service is treated as unsupported.
The CMS fact sheet MLN909160 is direct about the consequence. "We can deny payment for services with incomplete or illegible records." With missing or thin documentation, "there's no justification for the services or level of care billed." On claims already paid, CMS "may consider the payment an overpayment, which we can partially or fully recover."
When is psychotherapy medically necessary?
Medicare contractors publish the criteria in local coverage determinations. The Novitas policy L35101, Psychiatric Codes is a clear example. Other contractors publish their own psychiatry and psychology policies, so check the one for your region. The L35101 psychotherapy section sets five conditions.
The five conditions in the Medicare psychotherapy policy
Each condition below is quoted or closely paraphrased from L35101, with what a note has to show for a reviewer to see it.
| Condition in the policy | What the note has to show |
|---|---|
| A psychiatric illness, or emotional or behavioral symptoms "sufficient to cause inappropriate behavior or maladaptive functioning" | The diagnosis, and how the symptoms affect daily functioning: work, school, sleep, relationships, safety |
| "Clinically recognized therapies that are pertinent to the patient's illness or condition" | The named intervention used in the session, and why it fits this problem |
| Type, frequency and duration "medically necessary for the patient's condition under accepted practice standards" | Why this session length and this visit frequency, tied to severity |
| "A reasonable expectation of improvement", or maintenance where decline would otherwise be expected | Progress toward the plan's goals, or the risk of decline if care stops |
| "The capacity to actively participate in all therapies prescribed" | How the patient engaged and responded in the session |
One more line matters for long episodes of care. "The provider of service must document in the patient's record the medical necessity for continued (prolonged) treatments." A note in month nine has to explain why care is still needed.
What does Medicare require in a psychotherapy note?
L35101 has general rules for every psychiatric service and specific rules for psychotherapy. Together they form the minimum a reviewer looks for.
Required elements, by section of the policy
The left column is the policy's wording. The right column is where it goes in a note.
| Required by L35101 | Where it goes in the note |
|---|---|
| Legible record with patient identification and dates of service | Note header |
| Legible signature of the clinician responsible for the care | Signature block |
| Documentation that supports the medical necessity of the service | Assessment and plan |
| "The total number of timed minutes" | Start time, end time, total minutes |
| Time in the encounter and the "therapeutic maneuvers" applied | Intervention section |
| "Type of service (individual, group, family, interactive, etc.)" | Note header or CPT line |
| Content of session | Subjective and session content |
| Therapeutic techniques and approaches, including medications | Intervention section |
| Identity of the person performing the service | Signature block |
For group therapy the policy allows one shared group note with date, length and key issues. Each patient's record then gets an addendum on that patient's participation. Other group members' names should not appear in the note.
Time supports the code you bill, covered in the 90837 guide and the 90834 guide. It is also one of the general requirements in its own right.
How do you document medical necessity in a mental health note?
Write each note so a reviewer who has never met the patient can answer five questions from the page alone. The list below follows the policy conditions in order.
- Why is this patient in care? Name the diagnosis and one or two concrete ways it limits functioning right now. "Missed four workdays this month because of panic symptoms" carries more weight than "anxiety continues."
- What did you do? Name the intervention: cognitive restructuring, exposure, behavioral activation, motivational interviewing. A reviewer cannot infer a technique from "processed feelings."
- How did the patient respond? Describe engagement and what changed in the session. This is the policy's capacity condition.
- Is it working? Compare against the plan's goal, ideally with the same measure used on the plan. If progress has stalled, say what you are changing.
- Why continue? State the next step and the reason care is still needed at this frequency, or the risk if it stops.
Weak and stronger phrasing
The left column is the kind of line that leaves a reviewer guessing. The right column says the same thing in a way the record can defend.
| Leaves a reviewer guessing | Shows medical necessity |
|---|---|
| Client doing okay. | Sleep up to 6 hours most nights from 4 at intake; still avoiding the office, which is the plan's goal 2. |
| Discussed stressors. | Used cognitive restructuring on the belief "I will be fired"; client generated two alternative explanations. |
| Will continue therapy. | Continue weekly 53+ minute sessions: panic still prevents driving to work; review frequency at the next plan update. |
| Client participated. | Client completed the exposure step and rated distress 70 falling to 40 over the exercise. |
What do medical necessity documentation examples look like?
The three notes below are fictional and shortened. Each one shows the five answers in a different situation: active treatment, a group, and maintenance of a chronic condition.
Sample note 1: individual psychotherapy, major depressive disorder
- Service: individual psychotherapy, 10:02 to 10:56, 54 minutes, in person.
- Diagnosis and functioning: F33.1. Reports staying in bed until noon 4 of 7 days, missed two classes this week. PHQ-9 today 16, down from 19 at intake.
- Intervention: behavioral activation. Built a schedule of three morning activities linked to plan goal 1, return to full class attendance.
- Response: engaged, chose the activities herself, identified one barrier (no alarm) and solved it in session.
- Plan: weekly sessions continue while attendance is below target; repeat PHQ-9 in two weeks.
Sample note 2: group psychotherapy addendum, alcohol use disorder
- Group note on file: relapse prevention group, 90 minutes, 7 participants, topic high-risk situations.
- This patient: F10.20. Identified Friday paydays as his main trigger, linked to plan objective 2a. Practised a refusal script in a role play with the group.
- Response: participated in all exercises; reported 9 alcohol-free days, up from 3 last month.
- Plan: continue weekly group; individual session to rehearse the payday plan before Friday.
Sample note 3: maintenance, schizophrenia, stable
- Service: individual psychotherapy, 30 minutes, telehealth video.
- Diagnosis and functioning: F20.9. Living independently, attending day program 3 days a week. Two hospitalizations in the year before current treatment, none since.
- Intervention: reviewed early warning sign plan; rehearsed what to do when sleep drops.
- Response: named two early signs unprompted and his sister as the person to call.
- Plan: continue biweekly sessions to maintain current functioning; history shows decline when contact lapses.
Sample note 3 is maintenance care. The policy covers maintenance "where decline would otherwise be expected," so the note has to say what the decline risk is. "Stable, continue" does not.
What makes documentation insufficient?
CMS measures improper payments through its Comprehensive Error Rate Testing program, and MLN909160 lists what reviewers count as insufficient documentation. A claim is in error when the reviewer cannot tell whether services "were provided at the level billed, or were medically necessary."
Insufficient documentation, as CMS describes it
- Incomplete progress notes, meaning "insufficient detail to support you provided the service according to coverage requirements."
- Signature problems: "no provider signature, no supervising signature, illegible signatures without a signature log or attestation to identify the signer."
- A required element missing, such as an order, where the coverage policy makes it a condition of payment.
In a behavioral health chart, those gaps can look like this:
- Time recorded that does not support the code billed, or no time at all.
- A note that describes the session but never mentions the diagnosis or a functional problem.
- Wording that repeats from note to note, so no single session shows its own content or response.
- Progress described with no reference to the treatment plan's goals.
- A note signed so long after the session that it falls outside the clinic's own policy.
The L35101 notice adds a reminder for high-frequency care. "Medicare expects that patients will not routinely require the maximum allowable number of services." The more often you see someone, the more the record has to explain why.
How does medical necessity connect to the treatment plan?
The treatment plan is where medical necessity is set up. It records the diagnosis, the goals, the interventions and the frequency. Each progress note then reports against it. When a session moves to a problem the plan does not name, the note can be clinically right and still look unsupported. The plan was never updated to include it.
The treatment plan template guide covers the fields, measurable goals and review cadence. Number the plan's objectives and cite the number in each note, so the link is visible without a reviewer having to work it out.
How do you check medical necessity before the claim goes out?
A gap found in an audit or a denial is found after the claim is paid. A gap found before the claim leaves can still be fixed in the note. A short pre-claim review can follow the same five questions:
Pre-claim medical necessity check
- Diagnosis on the claim matches the diagnosis the plan treats.
- Note names at least one functional impact of the condition.
- Intervention is named and fits the plan's goals.
- Patient's response in the session is described.
- Progress or the reason to continue is stated.
- Start time, end time and total minutes support the billed code.
- Note is signed by the treating clinician within your policy's window.
Checking that by hand works for a sample of charts. In mdhub, chart audit checks every note against the rules your compliance team sets and flags what is missing before the claim is sent.
Sources
- CMS, MLN909160 Complying with Medical Record Documentation Requirements, December 2024
- Novitas Solutions, Local Coverage Determination L35101, Psychiatric Codes, revision effective January 1, 2024
- CMS Medicare Coverage Database, to find the psychiatric policy for your contractor
Write notes that show medical necessity
mdhub's clinical assistant, Emma, drafts the progress note from the session. The intervention, the patient's response and the time are captured while they are fresh. You review and sign. Start a free trial, or book a demo if you run a clinic with 10 or more clinicians.
Medical necessity documentation FAQ
The record must show the diagnosis and its functional impact, the intervention and the patient's response. It also needs progress or the reason to continue, the time and a signature.
Tie each note to a diagnosis and a functional problem. Name the intervention and describe the response. Then show progress against the treatment plan, or the risk of decline without care.
"Missed two classes this week due to depressive symptoms; used behavioral activation toward plan goal 1; PHQ-9 16 from 19; continue weekly."
It can. The Medicare psychotherapy policy covers maintenance of functioning where decline would otherwise be expected. The note must state that risk.
Yes. Medicare requires the medical necessity of each service reported to be clearly demonstrated in the record. That applies to every session.
No. A letter is a separate document for a payer or benefit plan. Medical necessity documentation is what the chart itself shows, note by note.
CMS can deny the claim, and on a paid claim treat the payment as an overpayment and recover it in part or in full.
