CMS-855 (Medicare Enrollment Application)
Medicare Enrollment Application
Family of Medicare enrollment applications: 855A (institutional), 855B (group), 855I (individual), 855O (ordering/referring), 855R (reassignment).
1 min read · Last reviewed May 23, 2026
At a glance
- Category
- Enrollment
- Acronym for
- Medicare Enrollment Application
- Primary sources
- 2
- Workspace handoff
- compliance binder →
Where this comes up
Credentialing and revenue-cycle staff handle this — CAQH ProView upkeep, payer-roster validation, NPI maintenance, PECOS revalidation cycles, and the gap between application and effective date that strands new providers. Lapses here block payment until backdated re-enrollment closes the gap.
Full definition
What it is in practice
CMS requires the appropriate 855 to enroll, change information, revalidate, or terminate. Most enrollments are completed in PECOS rather than on paper.
How it shows up in your practice
Track 855 submissions and effective dates. Provider effective date determines when claims can begin to be paid; mismatches cause claim rejections.
Sources
- CMS — Medicare Enrollment Formshttps://www.cms.gov/medicare/enrollment-renewal/providers-suppliers/enrollment-applications
- CMS — PECOShttps://pecos.cms.hhs.gov/pecos/login.do
Track 855 filings in the Compliance Binder
Open compliance binder →Related terms
- EnrollmentPECOS (Provider Enrollment System)The CMS online Provider Enrollment, Chain, and Ownership System used to submit and manage Medicare enrollment applications.
- EnrollmentProvider Enrollment RevalidationCMS requirement to periodically re-submit and validate enrollment information to remain Medicare-enrolled.
- EnrollmentNPI (National Provider Identifier)The 10-digit HIPAA standard identifier for health care providers.
- EnrollmentCAQH CredentialingThe CAQH ProView database used by most commercial payers to credential providers.
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Related across the archive
- GlossaryPECOS (Provider Enrollment System)The CMS online Provider Enrollment, Chain, and Ownership System used to submit and manage Medicare enrollment applications.
- GlossaryCAQH CredentialingThe CAQH ProView database used by most commercial payers to credential providers.
- GlossaryNPI (National Provider Identifier)The 10-digit HIPAA standard identifier for health care providers.
- GlossaryProvider Enrollment RevalidationCMS requirement to periodically re-submit and validate enrollment information to remain Medicare-enrolled.
- RegulationCMS-855B: Medicare Enrollment Application for Clinics and Group PracticesThe Medicare enrollment application for clinics, group practices, and certain other suppliers — the primary enrollment vehicle for medical practices that bill Part B.
- RegulationCMS-855I: Medicare Enrollment Application for Individual Physicians and Non-Physician PractitionersIndividual Medicare enrollment vehicle for physicians, NPPs, and certain other individual suppliers; required for any clinician billing Medicare under their own name.
- RegulationCMS-855A: Medicare Enrollment for Institutional ProvidersMedicare enrollment application for institutional providers including hospitals, CAHs, hospices, home health agencies, federally qualified health centers, rural health clinics, and similar entities.
- RegulationCMS-855O: Medicare Enrollment for Eligible Ordering and Certifying Physicians and Other Eligible ProfessionalsAbbreviated Medicare enrollment for clinicians who order or certify items and services for Medicare beneficiaries but do not personally bill Medicare.
This glossary entry is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at HHS, OCR, CMS, eCFR, NIST, and the relevant payer or industry body.