The CMS-855 application family

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.

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 reassignment application, which links an enrolled individual to a group or organization so that the group is paid for the individual's services. CMS publishes it together with the CMS-855I as a consolidated application, so exactly how and where a reassignment is filed follows the current CMS instructions.

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 reassigns benefits using the CMS-855R — now filed together with the CMS-855I under current CMS instructions — to a group already enrolled on the CMS-855B.

Several systems and companion forms sit alongside the 855 family. Before enrolling, an applicant must hold an NPI, the standard identifier issued through the national registry, because the NPI is referenced throughout the application. 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.

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.

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.