A CMN — Certificate of Medical Necessity — is documentation a treating physician completes certifying that a specific piece of DME meets Medicare's medical necessity requirements. Historically, Medicare required a CMN (or a related DME Information Form, or DIF) before it would pay for certain equipment categories, on top of the order itself. As of claims with dates of service on or after January 1, 2023, CMS eliminated the CMN and DIF requirement outright. The form is gone. The documentation obligation it stood for is not.

That distinction is where most of the confusion sits today, and it matters for anyone still building intake or billing workflows around "get the CMN signed." This guide covers what a CMN was, what CMS actually changed in 2023 and why, how a CMN differs from the Standard Written Order (SWO) that every DME item still requires, and what documentation still needs to exist even though the standalone form doesn't.

What does CMN stand for?

CMN stands for Certificate of Medical Necessity. It was a Medicare-specific form, completed and signed by the treating physician, certifying the elements Medicare needed to determine that a piece of durable medical equipment was medically necessary for a given patient: diagnosis, prognosis, the clinical reason for the equipment, and the estimated length of need. A related form, the DME Information Form (DIF), covered a narrower set of equipment categories and generally required less physician-level clinical detail, though a supplier still completed it using information from the medical record.

Neither form was the order. The order — what's being provided, to whom, and by whom — has always been a separate document, and that part didn't go away.

What changed: CMS eliminated CMNs and DIFs in 2023

CMS discontinued the CMN and DIF requirement as part of what the agency described as an effort to reduce unnecessary administrative burden for suppliers and physicians. The stated reasoning was straightforward: improvements in claims processing and medical record management meant the information a CMN or DIF collected was already available through the claim and the supporting medical record, making a separate certification form redundant.

The elimination applies to claims with dates of service on or after January 1, 2023, and covers eight specific DME categories and form sections that previously required a CMN or DIF:

• Oxygen therapy equipment
• Pneumatic compression devices
• Osteogenesis stimulators
• Transcutaneous electrical nerve stimulators (TENS)
• Seat lift mechanisms
• External infusion pumps
• Enteral and parenteral nutrition
• Section C continuation forms

The practical consequence for billing teams: a claim submitted on or after that date that still attaches a CMN or DIF isn't just unnecessary paperwork — CMS has indicated it can cause the claim to be rejected and require resubmission without the form. Intake workflows built around "print the CMN, get it signed, attach it to the claim" for these categories are working against the current requirement, not with it.

CMN vs. SWO: two different documents, only one of which still exists

The CMN and the Standard Written Order (SWO) get confused constantly because both involve a physician's signature on a document tied to a DME claim. They were never the same thing, and only one of them applies universally.

The SWO has been required for every DMEPOS item billed to Medicare since January 1, 2020, regardless of equipment category. It has to be communicated to the supplier before the claim is billed, and it must contain: the beneficiary's name or Medicare Beneficiary Identifier (MBI), the order date, a general description of the item (a description, the HCPCS code, or a brand name and model both work), the quantity if applicable, the treating practitioner's name or NPI, and the treating practitioner's signature. Signature stamps and date stamps aren't accepted.

The CMN, by contrast, was never required for every item — only for the eight categories listed above — and it existed on top of the SWO, not instead of it. Eliminating the CMN didn't touch the SWO requirement at all.

Do you still need something like a CMN today?

The form is gone, but the underlying obligation — proving medical necessity if a payer asks — is not. Medicare can still request supporting documentation through an Additional Documentation Request (ADR) or a Targeted Probe and Educate (TPE) review, and the medical record has to be able to answer the same questions a CMN used to: what's the diagnosis, why is this equipment medically necessary, and how long is it expected to be needed. That information now has to live in the physician's clinical notes and the order rather than on a standalone certification form.

A few categories carry documentation requirements beyond the SWO that are unrelated to the CMN/DIF elimination and still apply. Power mobility devices, for example, require a face-to-face encounter with the treating practitioner within a defined window in addition to the SWO. Oxygen equipment has its own local coverage determination testing requirements. None of that changed in 2023 — it was never part of the CMN/DIF rule to begin with.

Why this trips up DME intake and billing workflows

The most common way this shows up in practice: a legacy checklist or an older EHR template still routes oxygen, TENS units, or seat lift orders through a "get the CMN signed" step that no longer applies, while the actual requirement — a complete, correctly signed SWO plus medical-record documentation that supports necessity — gets treated as an afterthought. Denials for missing or incomplete SWO elements are common precisely because the SWO gets less attention than the form providers were trained for years to chase.

This is where document intake automation earns its keep. Seva AI reads incoming orders, SWOs, and supporting clinical notes as they arrive, extracts the required elements, and flags what's missing — a signature, an NPI, a quantity — before the order reaches sales order orchestration, rather than after a claim comes back denied. Combined with automated billing that checks claims against current payer rules before submission, that's one fewer place where a 2023 rule change quietly turns into 2026 denials. Providers evaluating DME billing services more broadly should ask specifically how a vendor's intake workflow handles SWO validation, since that's the document doing the work a CMN used to share.

For the broader vocabulary — DME, HME, DMEPOS, and how equipment categories get billed — see What Is DME? Durable Medical Equipment, Explained.