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Last updated
Short answer
A CMN is a Certificate of Medical Necessity: a CMS form that helped document the medical necessity and other coverage criteria for a few selected Medicare DMEPOS items. Since 2023, suppliers no longer submit CMNs for dates of service on or after January 1, 2023; claims with a CMN attached for those dates are rejected and returned. The legal order requirement is a separate document, the standard written order.
This page is general reference for lab, clinic and supply staff. It is not medical, coding or billing advice for any individual case.
Definition and scope: what a CMN is (and the DIF)
The CMS Medicare Program Integrity Manual (Pub. 100-08, chapter 5, Rev. 13689, issued 03-19-26) says a CMN or a DIF “is a form required to help document the medical necessity and other coverage criteria for selected DMEPOS items.” DMEPOS stands for durable medical equipment, prosthetics, orthotics and supplies. A DIF is a DME Information Form. The manual states the information on these forms is available on the claim or in the medical record and is redundant, which is why the requirement was removed.
Not every item ever needed one. The forms applied only to selected items, listed below. For the wider picture of how codes, orders and coverage fit together, see the guides on DME HCPCS codes and Medicare DME coverage.
Who fills in which section
A CMN has Sections A through D. According to chapter 5, section 5.5 of the manual:
- Sections A and C are completed by the supplier.
- Sections B and D are completed by the physician.
- A DIF is completed and signed by the supplier only. It needs no narrative description of equipment and cost and no physician signature.
- The supplier may not complete Section B. Knowing and willful completion of Section B carries a civil monetary penalty of up to $1,000 for each form or document.
What changed for 2023 dates of service
Section 5.5 (Rev. 11431, issued 05-26-22) says providers and suppliers “no longer need to submit these forms for services rendered after January 1, 2023.” The manual draws a line by date of service:
| Date of service | What the manual says |
|---|---|
| Before January 1, 2023 | Processes do not change. If a form was required, it is submitted or already on file with a previous claim. |
| On or after January 1, 2023 | Forms are not needed. Claims with a CMN or DIF attached are rejected and returned. |
The manual applies this statement everywhere it mentions CMNs or DIFs. The manual’s wording is that suppliers “no longer need to submit” the forms.
Which items had a CMN or DIF
Section 5.5 lists the OMB-approved forms (OMB 0938-0679):
| Form | Type | Item category |
|---|---|---|
| CMS-484 | CMN | Oxygen |
| CMS-846 | CMN | Pneumatic compression devices |
| CMS-847 | CMN | Osteogenesis stimulators |
| CMS-848 | CMN | TENS (the manual notes the TENS CMN is for purchases only) |
| CMS-849 | CMN | Seat lift mechanisms |
| CMS-854 | CMN | Section C continuation |
| CMS-10125 | DIF | External infusion pumps |
| CMS-10126 | DIF | Enteral and parenteral nutrition |
CMN versus the standard written order
The two are easy to confuse, and they are not the same thing. Section 5.2.1 states that all DMEPOS claims billed to Medicare require a written order or prescription from the treating practitioner as a condition for payment, with the elements codified at 42 CFR 410.38(d)(1) (eCFR). Section 410.38 itself does not mention a CMN.
| CMN / DIF | Standard written order (SWO) | |
|---|---|---|
| What it is | Form documenting coverage criteria for selected items | Condition of payment for all DMEPOS claims |
| Who completes it | CMN: supplier (A, C) and physician (B, D). DIF: supplier | Treating practitioner, who signs it |
| Status for dates of service on or after 2023-01-01 | Not submitted; rejected if attached | Still required |
Section 5.2.2 lists the SWO elements: beneficiary name or MBI; a general description of the item (general description, brand or model, HCPCS code or narrative); quantity to be dispensed, if applicable; order date; treating practitioner name or NPI; and the treating practitioner’s signature.
Under the older rules, a CMN could double as the order: the manual says it “can serve as the physician’s detailed written order if the narrative description in section C is sufficiently detailed.” For items needing both a CMN and a written order prior to delivery, such as seat lift mechanisms, a completed, physician-signed CMN could be used; otherwise a separate order was needed.
Where it matters for labs, clinics and suppliers
Timing of the order is the practical point that remains. Per section 5.2.4 and 42 CFR 410.38(d)(1)(ii)(A), for power mobility devices and items on the Required Face-to-Face Encounter and Written Order Prior to Delivery List, the order must be communicated to the supplier prior to delivery. For other DMEPOS items it must be communicated prior to claim submission. For listed items the practitioner must document a face-to-face encounter within the 6 months preceding the date of the written order (section 5.4.1, Rev. 13689, effective 04-20-26; 410.38(d)(2)). The List is selected from the Master List and published in the Federal Register and on the CMS website (410.38(c)(8)). The supplier keeps the written order, and the encounter is documented in the medical record (410.38(d)(3)).
Staff handling older claims should note the date-of-service split above: a pre-2023 date of service can still involve a CMN. For the supplier side of enrollment and standards, see DMEPOS supplier standards.
Common misunderstandings
- “A CMN is the same as a prescription.” It is not. The order is the separate condition of payment under 42 CFR 410.38.
- “Every DME item needed a CMN.” Only the selected items in the table above had a CMN or DIF.
- “The supplier can fill in the whole form.” The supplier may not complete Section B.
- “Attach one anyway to be safe.” For dates of service on or after January 1, 2023, a claim with a form attached is rejected and returned.
FAQ
What is a CMN?
A Certificate of Medical Necessity is a CMS form, completed partly by the supplier and partly by the physician, that documented medical necessity and coverage criteria for selected Medicare DMEPOS items. For dates of service on or after January 1, 2023, it is no longer submitted.
Is a CMN the same as a prescription or order?
No. The treating practitioner’s written order is the condition of payment under 42 CFR 410.38; a CMN was a separate form for selected items.
Do suppliers still send a CMN to Medicare?
Not for dates of service on or after January 1, 2023. The manual says claims received with these forms attached are rejected and returned.
Sources
- CMS, Medicare Program Integrity Manual, Pub. 100-08, chapter 5 (Rev. 13689, issued 03-19-26): cms.gov pim83c05.pdf, sections 5.2.1, 5.2.2, 5.2.4, 5.4.1 and 5.5. Checked 2026-11-01.
- eCFR, 42 CFR 410.38, DMEPOS scope and conditions: ecfr.gov section 410.38. Checked 2026-11-01.
