The CMS-855 application family
The CMS-855 forms are the family of Medicare enrollment applications that the Centers for Medicare & Medicaid Services (CMS) uses to add, update, and revalidate providers and suppliers in the program. Each form serves a distinct provider enrollment scenario — an individual practitioner, a group or clinic, an institutional provider, a reassignment of payment, or an order-and-refer-only role — and most can be filed on paper or electronically through PECOS. Which form applies depends on who is enrolling and why, not on preference.
Updated 7 min read
Reviewed by Anwaar Tayyab
Director of Billing Operations ·
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Key takeaways
- The CMS-855 family is Medicare-specific; each form maps to a particular enrollment scenario.
- The CMS-855I, 855B, 855A, 855O, and 855S each cover a distinct provider or supplier type or purpose, and CMS has merged reassignment reporting into the CMS-855I.
- The same applications are used to enroll initially, report changes, and revalidate.
- Most applications can be submitted electronically through PECOS, and paper versions also exist.
- Effective dates, revalidation cycles, and processing rules are set by CMS and change over time.
What the CMS-855 family is
The CMS-855 forms are a set of standardized applications, maintained by CMS, that providers and suppliers use to enroll in the Medicare program, report changes to their records, and periodically revalidate their information. Enrollment is the administrative step of being recognized by a payer so that claims can be adjudicated and paid; for Medicare, the 855 family is the vehicle for that step. The forms share a common structure but diverge by who is enrolling — a person or an organization — and by which part of the program the applicant participates in.
Enrollment is frequently confused with credentialing, the separate process of verifying a practitioner's qualifications through primary source verification. Filing a CMS-855 does not perform credentialing, and it does not create a commercial contract, which is handled through each plan's own payer contracting and applications. The distinction between the two ideas is covered in credentialing vs. enrollment and in the overview of what provider credentialing is.
Medicare-specific by design
The core applications
Each application corresponds to a role in the program. The correct form depends on whether the enrolling party is an individual or an organization, whether it will bill Medicare directly, and which benefit the applicant participates in. The most commonly encountered members of the family are below.
- CMS-855I
- The individual enrollment application, used by physicians and non-physician practitioners who enroll in Medicare in their own right.
- CMS-855B
- The application for clinics, group practices, and other organizational suppliers that bill Medicare Part B but are not individual practitioners, institutional providers, or equipment suppliers.
- CMS-855A
- The application for institutional providers — such as hospitals, skilled nursing facilities, home health agencies, and hospices — enrolling in Medicare Part A.
- CMS-855R
- The former reassignment application, which linked an enrolled individual to a group or organization so that the group is paid for the individual's services. CMS has merged that reassignment data into the CMS-855I and discontinued the CMS-855R, so a reassignment is now reported on the CMS-855I or in PECOS.
- CMS-855O
- The enrollment application for practitioners who only order, certify, or refer items and services and do not bill Medicare directly.
- CMS-855S
- The application for suppliers of durable medical equipment, prosthetics, orthotics, and supplies, which follows a separate enrollment process from the other 855 forms.
The split between the individual and group forms mirrors a broader distinction explored in individual vs. group enrollment. A single practitioner who bills in their own name relies primarily on the CMS-855I, while a practitioner whose payments flow to an employer or group typically enrolls on the CMS-855I and reports the reassignment on that same application — or in PECOS — to a group already enrolled on the CMS-855B.
Companion forms and PECOS
Several systems and companion forms sit alongside the 855 family. A provider or supplier that is eligible for an NPI, the standard identifier issued through the national registry, reports that identifier on its Medicare enrollment application, and an enrollment record that predates the NPI has to be updated to carry it. Applications can be completed on paper or, more commonly, electronically through PECOS, the CMS system of record for Medicare enrollment. The end-to-end electronic path is described in Medicare enrollment with PECOS.
Companion forms are often filed together with an 855. An electronic funds transfer authorization directs Medicare payments to a designated bank account, and a participation agreement records whether the provider accepts assignment as a participating provider. These are not part of the 855 series, but they are commonly submitted in the same package. The general shape of a submission — the applicant's identifying data, practice locations, and authorized signatures — parallels the structure discussed in the payer enrollment application.
Signatures and authorized officials
Matching the application to the scenario
Because the forms are role-based, most enrollment questions reduce to identifying the scenario and then selecting the application — and any companion forms — that fit it. The comparison below is illustrative; the authoritative mapping and any exceptions live in the current CMS enrollment guidance.
| Scenario | Primary CMS-855 application | Often filed alongside |
|---|---|---|
| A solo practitioner billing Medicare directly | CMS-855I | Participation and EFT companion forms |
| A practitioner joining a group that bills for them | CMS-855I, with the reassignment reported on it | The group's CMS-855B on file |
| A new group practice or clinic | CMS-855B | EFT companion form |
| An institutional provider under Part A | CMS-855A | EFT companion form |
| A practitioner who only orders or refers, without billing | CMS-855O | No billing-related companion forms |
Scenarios and requirements vary by provider type and change over time; confirm the current form set with CMS before filing.
Changes, revalidation, and effective dates
The 855 family is not only for initial enrollment. The same applications are used to report changes of information within timeframes that CMS sets and that vary by the type of change. Common events that prompt a filing include the following.
- A change of business address or the addition of a practice location
- A change of ownership or of managing or controlling interest
- The addition or termination of a reassignment of benefits
- Reportable final adverse legal actions
- Revalidation of the enrollment record when CMS requests it
CMS also requires periodic revalidation of Medicare enrollment on cycles that differ by provider and supplier type and that can change; providers are generally notified when revalidation is due. The maintenance rhythm — and how it relates to commercial recredentialing — is covered in revalidation and recredentialing.
Finally, the effective date of Medicare billing privileges, and any limited period of retrospective billing before that date, are governed by CMS regulation rather than by the applicant's preference. Because these rules change over time, current CMS guidance is the authoritative source, and the practical implications for scheduling and billing are discussed in effective dates.
Common questions
Is filing a CMS-855 the same as being credentialed?
No. A CMS-855 establishes or maintains enrollment and billing privileges with Medicare. Credentialing is a separate process of verifying a practitioner's qualifications through primary source verification, and commercial payers run their own credentialing and enrollment independently of the 855 forms.
What is the difference between the CMS-855I and the CMS-855R?
The CMS-855I enrolls an individual practitioner in Medicare in their own right. The CMS-855R was the separate form used to reassign that practitioner's Medicare benefits to a group or organization so the group is paid for the services. CMS has merged that reassignment reporting into the CMS-855I and discontinued the CMS-855R, so a practitioner joining a group now reports the reassignment on the CMS-855I or through PECOS.
Can CMS-855 forms be filed online?
Most can be submitted electronically through PECOS, the CMS system of record for Medicare enrollment, and paper versions of the forms also exist. The available channels and any requirements can change, so the current CMS instructions are the controlling reference.
How often must Medicare enrollment be revalidated?
CMS sets revalidation cycles that vary by provider and supplier type and that can change over time. Providers are generally notified when their revalidation is due; the specific interval should be confirmed against current CMS guidance rather than assumed.
Do commercial payers use the CMS-855?
No. The 855 family is Medicare-specific. Medicaid programs and commercial plans maintain their own enrollment applications and systems, so completing a CMS-855 does not enroll a provider with those payers.
Key terms in this article
Defined once, on their own pages.
Continue learning
Where to go next on Medicare enrollment and how it fits the wider credentialing picture.
Medicare enrollment with PECOS
How the electronic enrollment system handles the 855 forms end to end.
Individual vs. group enrollment
When a practitioner enrolls in their own name versus reassigning to a group.
The payer enrollment application
The common structure shared by enrollment applications across payers.
Revalidation and recredentialing
Keeping enrollment and credentials current after the first approval.
Credentialing vs. enrollment
Why verifying qualifications and gaining billing privileges are different steps.
Authoritative sources
- Medicare enrollment applications (opens in a new tab)
CMS. Lists the current paper enrollment applications by enrolling party — CMS-855A for institutional providers, CMS-855B for clinics and group practices, CMS-855I for physicians and non-physician practitioners, CMS-855O for ordering and certifying practitioners, and CMS-855S for DMEPOS suppliers — states that they can be used for initial enrollment, revalidations, changes in status, and voluntary termination, names the CMS-588 electronic funds transfer authorization and the CMS-460 participating agreement as the forms routinely submitted with an enrollment, and routes DMEPOS applications to their own enrollment contractors.
- Consolidated CMS-855I/CMS-855R Enrollment Applications (opens in a new tab)
CMS. States that Medicare merged the CMS-855R into the CMS-855I paper enrollment application, that all data previously collected on the CMS-855R is now captured on the CMS-855I, that the CMS-855R is discontinued, and that practitioners enroll and report reassignments either through PECOS or on the paper CMS-855I.
- 42 CFR 424.506 — National Provider Identifier (NPI) on all enrollment applications and claims (opens in a new tab)
eCFR. Requires a provider or supplier that is eligible for an NPI to report its NPI on its Medicare enrollment application, and requires an existing Medicare enrollment record that does not carry the NPI to be updated with it using either the applicable paper CMS-855 form or internet-based PECOS.
- 42 CFR 424.510 — Requirements for enrolling in the Medicare program (opens in a new tab)
eCFR. Requires a complete enrollment application and supporting documentation to be submitted to the designated Medicare fee-for-service contractor, sets what the application must contain, requires an authorized official to sign the certification statement on behalf of an organization, requires agreement to receive Medicare payments by electronic funds transfer on the CMS-588, and reduces the requirements for a practitioner enrolling solely to order and certify.
- 42 CFR 424.516 — Additional provider and supplier requirements for enrolling and maintaining active enrollment status in the Medicare program (opens in a new tab)
eCFR. Sets the events a provider or supplier must report to its Medicare contractor and the timeframes for reporting them, including a change of ownership or control, an adverse legal action, and a change, addition, or deletion of a practice location.
- 42 CFR 424.515 — Requirements for reporting changes and updates to, and the periodic revalidation of Medicare enrollment information (opens in a new tab)
eCFR. Establishes the periodic revalidation of enrollment information, provides that CMS contacts each provider or supplier directly when revalidation is due, reserves the right to revalidate off cycle and to adjust the schedule, and routes ambulance and DMEPOS suppliers to their own separate cycles.
- 42 CFR 424.520 — Effective date of Medicare billing privileges (opens in a new tab)
eCFR. Sets by regulation when Medicare billing privileges take effect, tying the date for physicians, non-physician practitioners, and their organizations to the later of the filing of a subsequently approved enrollment application or the date services first began at the new practice location.
- 42 CFR 424.521 — Request for payment by certain provider and supplier types (opens in a new tab)
eCFR. Sets the limited retrospective billing available to a listed set of provider and supplier types for services furnished at the enrolled practice location before the enrollment's effective date.