Medicare does not use one enrollment application for everyone. It uses a family of CMS-855 forms, and the one you file depends on what kind of entity is asking to bill. Pick the wrong one and the application is returned before anyone looks at the substance. Pick the right one but miss a companion filing, and claims can deny even after you are approved.
This guide is for owners and administrators who need to decide which form fits their organization: a hospital or agency, a clinic or group, or an individual clinician. It explains the three most common forms at a high level, how they fit together, and the questions to ask before you start. It is not a line-by-line walkthrough. If you want the full catalog of 855 forms, including the 855O and 855S, see our CMS-855 form guide.
The short answer
- CMS-855A is for institutional providers that bill Medicare Part A, such as hospitals, home health agencies, hospices and skilled nursing facilities.
- CMS-855B is for clinics, group practices and certain other suppliers that bill Part B as an organization.
- CMS-855I is for individual physicians and non-physician practitioners who render Part B services.
Many organizations need more than one. A medical group files a 855B for the group and an 855I for each clinician. A hospital that also runs an outpatient physician practice may hold a 855A enrollment and a separate 855B enrollment. The form follows the billing entity, not the building.
The CMS-855A: institutional providers
CMS describes the 855A as the enrollment application for institutional providers. In practice that means organizations that are certified to participate in Medicare and usually bill under Part A, including:
- Hospitals, including critical access hospitals
- Skilled nursing facilities
- Home health agencies and hospices
- Rural health clinics and federally qualified health centers
- Community mental health centers, comprehensive outpatient rehabilitation facilities and similar certified providers
What sets the 855A apart is that enrollment is only one track. Most 855A providers also need certification, through a state survey agency or an approved accrediting organization, and a provider agreement with CMS. The Medicare contractor reviews the application and makes a recommendation, but the organization is not billing until the certification side is also complete. That two-track structure is why 855A projects benefit from a single plan that covers licensing, survey or accreditation, and enrollment together. Our article on home health licensing and Medicare certification shows how those tracks interact for one provider type.
The CMS-855B: clinics, groups and organizational suppliers
The 855B is the application for organizations that bill Part B. The most common filers are:
- Physician group practices and non-physician practitioner groups, whether two clinicians or two hundred
- Multi-specialty clinics
- Ambulatory surgical centers
- Independent diagnostic testing facilities, portable x-ray suppliers and similar diagnostic suppliers
- Ambulance service suppliers
- Mass immunization roster billers and certain other organizational supplier types listed on the form
A 855B enrollment gives the organization its own Medicare billing privileges. It does not enroll the people who work there. Each clinician who renders services and wants the group to bill for them still needs an individual enrollment and a reassignment of benefits to the group. That last link is easy to overlook, and it is one of the most common reasons a newly enrolled group sees denials. Our reassignment guide explains how that link works today.
One more point that causes confusion: a solo clinician who has formed a professional corporation or LLC and bills through it may be able to enroll on an 855I as the sole owner, rather than filing a separate 855B. Whether that fits depends on how the entity is set up and billed, so it is worth confirming before you file.
The CMS-855I: individual practitioners
The 855I enrolls an individual physician or non-physician practitioner, such as a nurse practitioner, physician assistant, clinical psychologist, clinical social worker, or, since 2024, a marriage and family therapist or mental health counselor. It establishes that clinician's own Medicare billing privileges and records where they practice and who, if anyone, bills on their behalf.
We cover the 855I in depth in our 855I guide, so here the key point is how it relates to the other two forms. An 855I almost never stands alone inside an organization. It sits alongside the group's 855B, or alongside a facility's 855A when clinicians at that facility bill professional services separately.
How the three fit together: common scenarios
A new two-clinician group practice
The group files a 855B. Each clinician files or updates an 855I and reassigns benefits to the group. If either clinician was already enrolled elsewhere, that existing enrollment needs to be updated rather than duplicated.
A new home health agency or hospice
The agency files a 855A, alongside state licensure and survey or accreditation. A medical director who bills Medicare for professional services may also need an 855I, depending on the arrangement.
A hospital adding an outpatient practice
The hospital's existing 855A enrollment does not automatically cover a separately billing physician practice. That practice may need its own 855B, and its clinicians need 855I enrollments and reassignments to the right entity.
A clinician leaving one group for another
No new 855B is needed. The clinician's 855I information and reassignment are updated to end the old link and create the new one.
The application fee: who pays and who does not
Medicare charges an enrollment application fee to institutional providers and suppliers. CMS sets the amount each calendar year, and for CY2026 the fee is $750. It applies when an institutional provider or supplier initially enrolls, adds a practice location, or revalidates.
In practical terms, most 855A filers pay it, and organizational suppliers filing a 855B, such as an ambulatory surgical center or an IDTF, pay it as well. Three groups are exempt:
- Individual physicians and non-physician practitioners filing an 855I
- Physician groups and non-physician practitioner groups filing a 855B
- Reassignments of benefits (historically filed on the CMS-855R, now reported through the 855I)
A provider can request a hardship exception, which CMS decides case by case. Always check the current amount on CMS's application fee page before you submit, because it changes each January.
Screening, site visits and what comes after approval
CMS screens every applicant at a risk level set by regulation. Some provider and supplier types fall into a moderate or high screening category, which can mean an unannounced site visit and, for high risk, fingerprinting of certain owners. Newly enrolling home health agencies, for example, are screened at a higher level than most physician groups. Knowing your category ahead of time helps you make sure the location, signage, staff and records are ready to be seen.
Enrollment is also not a one-time event. Most providers and suppliers revalidate every five years, CMS can request off-cycle revalidation, and changes such as a new location, a new owner or a new authorized official must be reported within set timeframes. Our revalidation guide covers that cycle.
Questions to answer before you pick a form
- Which legal entity will submit claims, and under which tax ID?
- Is that entity certified to participate in Medicare (Part A), or is it a supplier billing Part B?
- Which individuals will render services, and are any of them already enrolled under another group?
- Who are the owners, managing employees and authorized officials, and are their records consistent across NPPES, PECOS and state records?
- Does the organization owe the application fee, and is that fee paid before submission?
If any of those answers are unclear, sort them out first. Most avoidable delays start with a form that was chosen or completed before the business structure was settled. Our article on why Medicare applications get rejected covers the patterns we see most.
How Maverick can help with choosing and filing the right 855
Choosing a form sounds like a small decision, but it shapes everything after it. Here is why practices and facilities bring this work to us:
- We map your structure first. Before anything is filed, we look at your entities, owners, locations and clinicians and tell you which 855 forms you need and which existing enrollments should be updated rather than duplicated.
- A complete and accurate file. We line up your NPPES, PECOS, licensing and ownership details so the application agrees with itself and with every other system the contractor checks.
- Prompt submission. Once your file is complete, we submit. Nothing sits in a queue on our side.
- Regular follow-up. We follow up with the Medicare contractor on a set schedule and respond to development requests on your behalf.
- Keeping you updated. You always know where each application stands and what, if anything, we need from you.
What we do not control is how long Medicare takes to review and approve an application. That decision belongs to CMS and its contractors, and we will never promise a date on their behalf.
Opening a new group? Our Maverick Launch: Group package sets up the group and every clinician, including the 855B, each 855I and the reassignments. Already enrolled? Autopilot keeps revalidations and change reporting on track so your enrollment stays active. Facilities and other organizations get a custom scope through our Medicare and Medicaid enrollment service.
Sources: CMS-855A, CMS-855B and CMS-855I Medicare Enrollment Applications (CMS.gov, Medicare enrollment forms); CMS Medicare Enrollment Application Fee page (CY2026 fee); Medicare Program Integrity Manual, Chapter 10 (CMS Pub. 100-08); 42 CFR 424.514 (application fee), 424.518 (screening levels) and 424.515 (revalidation). Verified October 2026.