CMS-855O: Ordering & Referring Provider Enrollment

The CMS-855O is for physicians and eligible non-physician practitioners who need to order or refer Medicare services — such as DMEPOS, home health, or clinical lab services — but who do not bill Medicare for their own services.

The key distinction: you don’t need Medicare billing privileges to order a walker for your patient. But you do need to be enrolled in Medicare as an ordering/referring provider — via the CMS-855O — or the Medicare claim for that walker will be denied.

This rule catches many providers by surprise, especially those in practice settings that don’t bill Medicare directly but who serve Medicare patients.

The ordering/referring rule explained

Medicare implemented the ordering/referring rule in 2010. Under this rule, a claim for a covered Medicare service that requires a physician order or referral will be denied if the ordering/referring provider is not enrolled in Medicare or does not have a valid opt-out on file.

This means:

• A DMEPOS supplier cannot be paid for equipment ordered by a non-enrolled physician
• A home health agency cannot receive Medicare payment for services ordered by a non-enrolled physician
• A laboratory cannot receive Medicare payment for tests ordered by a non-enrolled physician

The supplier or service provider bears the risk — they don’t get paid if the ordering provider isn’t properly enrolled. As a result, many DME suppliers, home health agencies, and labs actively check provider enrollment status and will not accept orders from providers who aren’t enrolled.

Who needs the CMS-855O

You need to file the CMS-855O (or already have an active CMS-855I or CMS-855B enrollment) if you are a:

• Physician or osteopathic physician who orders DMEPOS, home health, clinical lab, or imaging for Medicare patients
• Nurse practitioner who orders any of the above
• Physician assistant who orders any of the above
• Clinical nurse specialist
• Certified nurse-midwife
• Any other practitioner who may order Medicare-covered services

You do not need the CMS-855O if:

• You already have an active CMS-855I or CMS-855B Medicare enrollment — your existing enrollment covers ordering/referring privileges
• You have an active Medicare opt-out affidavit on file
• You never order or refer Medicare-covered services

When CMS-855O vs. CMS-855I

The CMS-855O is a limited enrollment — it grants ordering/referring privileges only. It does not grant billing privileges.

If you think you might ever want to bill Medicare directly — even in the future — file the CMS-855I instead. It’s more work but creates full enrollment. Switching from CMS-855O to CMS-855I later requires a separate enrollment application.

Step-by-step: Filing the CMS-855O

Via PECOS

Step 1: Log in to PECOS Use your individual I&A credentials. If you don’t have one, create an I&A account first.

Step 2: Start a CMS-855O enrollment Select “Ordering/Referring Enrollment” from the enrollment options.

Step 3: Enter your information

• Legal name (must match your NPI record exactly)
• NPI (Type 1 — your individual NPI)
• Specialty/taxonomy code
• Practice location(s)

Step 4: Adverse legal history Same as other 855 forms — disclose all adverse actions.

Step 5: Sign and submit

Via paper

Download the current CMS-855O from cms.gov. Complete and mail to your MAC.

⚠️ Risk flags

⚠️ Your patients’ suppliers are at risk. If you’re not enrolled as an ordering/referring provider and you order DMEPOS or home health for Medicare patients, the supplier won’t be paid — and they know it. Many suppliers will refuse orders from non-enrolled providers or ask you to document your enrollment status. Get enrolled before this becomes a problem with a supplier or patient.

⚠️ CMS-855O doesn’t expire with enrollment. If you move from CMS-855O ordering/referring status to full CMS-855I billing status, the CMS-855O doesn’t automatically terminate. You should notify your MAC to ensure your records are clean.

⚠️ Opt-out providers. Physicians who have filed a Medicare opt-out affidavit do not need the CMS-855O — their opt-out covers ordering/referring. If you have an opt-out on file and it’s current, you’re covered.

Common errors

Error: Claims denied — ordering provider not enrolled Cause: Provider ordered DMEPOS or home health but isn’t in PECOS as ordering/referring. Fix: File the CMS-855O (or CMS-855I) immediately. Note that there is no retroactive fix — denied claims stay denied until the provider is enrolled, and even then only future claims benefit.

Error: Provider has both CMS-855I and CMS-855O active Cause: Provider switched from 855O to 855I without terminating the 855O. Fix: Contact your MAC to clean up the record. Duplicate enrollments can create billing complications.

Processing timeline

CMS-855O processing is generally faster than CMS-855I because there’s no billing privilege setup involved.

Related forms

• CMS-855I — Individual Provider Enrollment (full billing privileges)
• Medicare Opt-Out Affidavit
• DME & DMEPOS Provider Hub

Not sure if you need the CMS-855O or the CMS-855I? Ask Mae →