CMS-855I Form: How to Complete It, Section by Section

Published November 3, 2026

The CMS-855I is the Medicare enrollment application for individual physicians and other eligible professionals who bill Medicare. This walks through it in order, using the current version, CMS-855I (05/23), and only what the form itself says. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners.)

Who files the 855I

All physicians, and all eligible professionals as defined in the Social Security Act, complete the 855I to enroll and get a Medicare billing number. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.) It covers more than a first enrollment: revalidating, reactivating, moving to another MAC, reporting changes, reassigning benefits and voluntarily ending enrollment. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.)

• Reassignments: the CMS-855R has been discontinued, and reassignments are now reported on the 855I. Both you and the group must be enrolled, or enrolling at the same time with the group on the CMS-855B. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.)
• Sole owners adding an authorized or delegated official: use the CMS-855B, not the 855I. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.)

You can apply in PECOS or on the paper form. A paper 855I must be typed, not handwritten, and goes to your MAC with original signatures and all required documents. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.)

Section 1: Basic information

Check one reason for submitting in 1A, such as new enrollment, revalidation, reactivation or a change of information. If you are reporting a change, check what is changing in 1B. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 1.) Picking the wrong reason is an easy way to have the application returned or rejected: see why 855I applications get rejected.

Section 2: Personal identifying information

Your name, SSN, date of birth, NPI and PTAN if you have one, then licenses, certifications and DEA registration, mailing and medical record correspondence addresses, and your specialty: one primary and any secondary physician specialties, or one non-physician specialty type. Some professions have their own part, such as psychologists, therapists in private practice, and nurse practitioners and clinical nurse specialists. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 2.)

The name and SSN in 2A must be the same ones you used to get your NPI, and must match exactly in PECOS and NPPES. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 2.) If NPPES shows something different, fix that first: see NPI not active in NPPES.

Section 3: Final adverse legal actions

Report any convictions in the preceding 10 years, exclusions, revocations, suspensions and other final adverse legal actions, whether or not they were expunged or are under appeal. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 3.)

Section 4: Business information

• 4A, private practice: how your practice is structured, and the entity's legal business name, TIN, PTAN and NPI where they apply. The legal business name and TIN must match the ones on your NPI and the IRS records. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 4 and page 2.)
• 4B, practice locations: every location where you see patients, as a street address, not a P.O. box, with the primary location marked. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 4B.)
• 4C, remittance notices and special payments: where those go. Routine payments are made by electronic funds transfer. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 4C.)

Section 12: Supporting documents

Section 12 lists what to attach. For most practitioners that means the CMS-588 EFT agreement with a voided check or bank letter, IRS confirmation of a TIN and legal business name when one applies, and documentation of any adverse legal actions. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 12.) The MAC can ask for more, and you have 30 days to provide it. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, page 1.) Missing documents are a rejection reason. (Source: 42 CFR 424.525, rejection of an enrollment application, (a)(2).)

Section 15: Certification and signature

Sign and date section 15. For a reassignment, 15B is signed by you and 15C by a delegated or authorized official of the group. (Source: CMS-855I (05/23), Medicare enrollment application for physicians and non-physician practitioners, section 15.) In PECOS, the MAC will not fully process the application without your electronic or uploaded signature. (Source: CMS MLN9658742, Medicare Provider Enrollment (December 2025).)