CMS-855I: The Medicare Enrollment Application for Physicians and Non-Physician Practitioners

CMS-855I is titled "Medicare Enrollment Application — Physicians and Non-Physician Practitioners." Its who-should-submit statement, quoted from the current form as fetched on 11 August 2026: "All physicians, as well as all eligible professionals as defined in section 1848(k)(3)(B) of the Social Security Act must complete this application to enroll in the Medicare program and receive a Medicare billing number."

Initial enrollment is only one of the scenarios the form lists. Complete a CMS-855I, per the form's own instructions, if you are an individual practitioner or eligible professional who plans to bill Medicare and you are:

• Enrolling in Medicare for the first time as a new enrollee
• "An individual practitioner or eligible professional who has formed a professional corporation, professional association, limited liability company, etc., of which you are the sole owner" — the sole-owner scenario covered in detail below
• Currently enrolled only to order and certify and now want to submit claims for services rendered
• Responding to a revalidation notice — a provider revalidates enrollment on this same form, not a separate one
• Reactivating a previously enrolled billing number to resume billing
• Enrolling in another Medicare Administrative Contractor's (MAC's) jurisdiction because you opened a practice location in territory another MAC services
• Reporting changes to enrollment information, such as an added or changed practice location
• A physician, physician assistant, nurse practitioner, or clinical nurse specialist furnishing acupuncture services
• Establishing, terminating, or changing a reassignment of Medicare benefits — for the practitioner side or the organization/group side
• Voluntarily terminating your Medicare enrollment, including all reassignments

The sole-owner scenario deserves the emphasis the form gives it, because it is where the 855I-versus-855B choice actually confuses people. A physician who owns 100% of their PC or PLLC does not enroll that entity on the organization form — the CMS-855I handles the practitioner and the solely-owned entity together. The form carves out an exception: "If you are a sole owner and intend to add an Authorized/Delegated Official to your Medicare enrollment, do not complete the CMS-855I application; rather, use the CMS-855B application." An incorporated individual will typically hold two NPIs — CMS's NPI fact sheet states an incorporated individual "can obtain an NPI for themselves (Type 1) and an NPI for their corporation or LLC (Type 2)" — and our Type 2 NPI guide walks through which entity types need which.

One prerequisite gates everything: NPPES assigns the NPI, and it must exist before the 855I is filed. The form states you "must obtain an NPI and furnish it on this application prior to enrolling in Medicare," and CMS's MLN booklet on the NPI (ICN 902603) removes any doubt about what happens otherwise: "An enrolment application without an NPI will be rejected." Getting the NPI is Step 1 of CMS's own four-step Medicare enrollment sequence; the PECOS application is Step 2.

Four form numbers, one recurring question. Every row in this table is grounded in the named form's own current text, fetched 11 August 2026.

855I or 855B. The dividing line is who receives the billing number. An organization enrolls in Medicare through PECOS using CMS-855B — the 855B's own instruction reads: "Clinics, group practices, and other suppliers must complete this application to enroll in the Medicare program and receive a Medicare billing number." A practitioner enrolls in Medicare using CMS-855I. A new group therefore usually needs both: the 855B for the entity, an 855I per practitioner, with the reassignment connecting them. The one entity that files an 855I instead of an 855B is the solely-owned PC/PA/LLC, per the sole-owner language quoted in the previous section. Our CMS-855B guide covers the organization side, including the 855B-versus-855A boundary this page deliberately skips.

855I or 855O. The 855O exists for practitioners who need to be in Medicare's system without ever billing it. Its own text: physicians and eligible professionals "can apply to enroll for the sole purpose of ordering or certifying items and/or services to beneficiaries in the Medicare program," and — the operative sentence — "These physicians and eligible professionals do not and will not send claims to a Medicare Administrative Contractor (MAC) for the services they furnish." A VA-employed physician who orders DMEPOS, a licensed resident, a dentist who refers for covered services: 855O. Anyone who will submit a claim: 855I. The 855I's scenario list even includes the crossover case — a practitioner "currently enrolled in Medicare to order and certify" who now wants "to enroll as an individual practitioner to submit claims for services rendered" files the 855I.

855R. The current 855I states it on its opening pages: "NOTE: All reassignment actions should now be reported via the CMS-855I. The CMS-855R (Reassignment of Medicare Benefits) form has been discontinued." CMS's Provider Enrollment & Oversight Group dated the change precisely in its 2024 compliance-conference keynote: the consolidated 855I was "Released on September 1, 2023" and the "855R was discontinued effective October 31, 2023." CMS then rewrote its Program Integrity Manual to match — Transmittal 12639 (May 16, 2024) retitles the manual section "Reassignment of Medicare Benefits Via the Form CMS-855I" and deletes the former CMS-855R sections outright.

A fee footnote for the comparison: per CMS's MLN Medicare provider enrollment page, "Physicians, non-physician practitioners (NPPs), physician organizations, non-physician organizations, and Medicare Diabetes Prevention Program (MDPP) suppliers don't pay a Medicare enrollment application fee." The 2026 application fee — $750 — falls on institutional-type suppliers, not on 855I filers. The FAQ below covers this in full.

The form gives you two routes. Its instruction: practitioners "can apply for enrollment in the Medicare program or make a change to their enrollment information (including adding or terminating a reassignment of benefits) using either: the Internet-based Provider Enrollment, Chain and Ownership System (PECOS), or the paper CMS-855I enrollment application."

CMS's stated preference is not subtle. Its PECOS enrollment page says: "Because PECOS is paperless, you no longer need to submit anything by mail. Additionally, PECOS applications tend to process faster than paper applications." The MACs publish numbers that back this up — as goals, not guarantees, which is exactly how they frame them. National Government Services states on its provider-enrollment page (reviewed by NGS on 2 September 2025): "All MACs, including National Governments Services, have a goal to finalize an Internet-based PECOS application within 15 days and a CMS-855 paper application within 30 days, if all required information is available." Novitas Solutions publishes CMS-defined processing timeframes with percentile bands: internet-based PECOS initial enrollments that need no site visit, development, or fingerprinting are 95% completed within 15 calendar days and 100% within 50 calendar days of receipt; paper applications without those events run 95% within 30 days and 100% within 65 days, and with them 95% within 65 days and 100% within 100 days. Read the conditional in both: "if all required information is available" and "do not require development." A single development request moves your application out of the fast band — which is why the completeness discipline in the next section is worth more than any submission-route choice. Neither MAC's figures are promises, and we quote them as published timeframes only.

If you file on paper anyway: the form "must be typed. It may not be handwritten," and it goes to your MAC, not to CMS — "Send this completed application with original signatures and all required documentation to your designated MAC. The MAC that services your State is responsible for processing your enrollment application." The form points to CMS.gov's provider-enrollment section to look up your MAC's enrollment mailing address.

One access-control point that billing companies routinely get wrong: PECOS logins run through the Identity & Access (I&A) Management System, and CMS's I&A terms state "Sharing of login information is strictly prohibited!" The compliant pattern is the one the system is built for — the Authorized Official signs, and a surrogate works on the provider's behalf through the Identity & Access (I&A) Management System via an approved surrogate connection. No vendor needs your password; a vendor who asks for it is proposing a terms-of-service violation on a federal system. Our PECOS enrollment guide covers I&A account setup, roles, and surrogate connections in depth.

For a new enrollee, the form's Section 1A instruction is simply "Complete all applicable sections." That is less helpful than it sounds, so here is what the sections actually ask for, drawn from the form fetched 11 August 2026. Existing enrollees reporting changes get a lighter load — Section 1B maps each change type to a specific section combination (a reassignment change, for example, is "1, 2A, 4F, 12, 13 (optional) and 15").

Section 1: Basic information

Check the reason for the application — new enrollee, order/certify conversion, new MAC jurisdiction, revalidation, reactivation, change of information, or voluntary termination. Everything downstream keys off this box.

Section 2: Personal identifying information

Section 2A is the identity core: name, date of birth, SSN, existing PTAN if issued, and your Type 1 (Individual) NPI. The form's rule: "The provider's Name, Date of Birth, and Social Security Number must match his/her social security record." 2B captures license, certification, and DEA registration details, including whether your license is a compact license. 2C is an optional accepting-new-Medicare-patients question. 2D is the correspondence mailing address, with a restriction that catches practices using their biller as a mail drop: "This address cannot be a billing agent or agency's address or a medical management company address." 2G (physicians) or 2H (non-physician practitioners) is the specialty grid — and note the form's constraint: "You can only select one primary specialty. If you have multiple primary specialties, you must complete and submit a separate CMS-855I application for each primary specialty."

Section 3: Final adverse legal actions

Convictions, exclusions, license revocations and suspensions. Report applicable history here rather than hoping it goes unnoticed — the MAC screens against these databases anyway, and an unreported action is its own problem.

Section 4: Business and practice information

4A carries the private-practice business information, and it holds the single most consequential matching rule on the form: "the Legal Business Name (LBN) and Tax Identification Number (TIN) you furnish in section 4A must be the same Name, SSN, LBN and TIN you used to obtain your NPI. Once this information is entered into PECOS from this application, your Name, SSN, LBN, TIN and NPI must match exactly in both PECOS and NPPES." Exactly means exactly — the LBN comes from your IRS documentation (the CP-575 for an EIN), not from your signage or your website. 4B reports each practice location; 4F is the reassignment subsection covered in the next section of this guide.

Sections 6 and 8: Managing employees and billing agency

Section 6 identifies managing employees; Section 8 discloses a billing agency relationship if claims will be submitted by one.

Sections 12, 13, and 15: Documents, contact person, signatures

The form's cover page says it directly: "SEE SECTION 12 FOR A LIST OF SUPPORTING DOCUMENTATION TO BE SUBMITTED WITH THIS APPLICATION." Section 13 names a contact person and is optional. Section 15 is the certification statement — the form's tips list closes with "Sign and date section 15," and unsigned or wrongly-signed 15s are the classic silent killer of otherwise-complete packages.

The form's own anti-delay checklist

The 855I publishes its tips to avoid delays, and they read like a rejection post-mortem: complete all required sections as shown in Section 1; "Ensure that the Legal Business Name shown in section 4 matches the name on the tax documents"; ensure the Section 2 correspondence address is the provider's own; enter your NPIs in the applicable sections; "Include the Electronic Funds Transfer (EFT) Authorization Agreement (when applicable) with your enrollment application with a voided check or bank letter" — CMS-588 authorizes electronic funds transfer and rides along with the enrollment package when EFT is being established; sign and date Section 15; and send all supporting documents to your designated MAC. Our provider enrollment checklist turns this into a stage-everything-first document list so the application goes out complete the first time.

Since the 855R's discontinuation, the 855I is where a practitioner reassigns benefits to the group. The form defines the transaction: "Reassignment of Medicare Benefits: Authorization by an individual practitioner to allow an eligible organization/group to submit claims and receive payment for Medicare Part B services that the practitioner has provided as a member of the organization/group."

On the paper form, a reassignment change is the "Reassignment of Benefits Information" row of Section 1B — sections 1, 2A, 4F, 12, 13 (optional) and 15 — with 4F holding the reassignment details. The signature choreography is precise and unforgiving:

• New reassignment: "Section 15B must be signed by the individual practitioner and Section 15C must be signed by a delegated/authorized official of the organization/group. If the reassignment is to an individual, that person must sign Section 15C." The form adds that a new reassignment is generally established, signed, and submitted by the organization/group.
• Termination or change: one signature suffices — "either the organization/group must sign Section 15C or the individual practitioner must sign Section 15B." After a termination's effective date, reassigned claims for the practitioner's services are no longer paid to the group.

The prerequisite most new groups hit: "Both the individual practitioner and the eligible organization/group must be currently enrolled (or concurrently enrolling via submission of the CMS-855B for the eligible organization/group and the CMS-855I for the individual practitioner) in the Medicare program before the reassignment can take effect." A reassignment to a group that has no Medicare enrollment yet goes nowhere — which is why a new group's filing order is 855B for the organization, 855I per practitioner, reassignment linking the two, submitted together as concurrent enrollments.

For the full post-2023 workflow — adding a physician to a group today in PECOS or on paper, terminating a reassignment, and what happens if someone mails in an old 855R — see our CMS-855R discontinuation and reassignment guide.

The MAC processes the application and issues the PTAN. Between submission and approval sits the step that determines whether you land in the fast processing band: the development request. If information or documents are missing, the MAC asks — and the form states the deadline: "You are responsible for providing this documentation within 30 days of the request per 42 C.F.R. section 424.525(a)(1) and (2)." Miss the development window and the application can be rejected, which restarts the clock from zero.

Approval arrives as a letter, and the letter carries the number you have been waiting for. CMS's MLN glossary defines it: "A PTAN is a Medicare-only number issued to health care professionals or suppliers by Medicare Administrative Contractors (MACs) upon enrollment in Medicare. When a MAC approves enrollment and issues an approval letter, the letter will include the PTAN assigned to the health care professional or supplier." The same glossary sets the NPI relationship: "A health care professional or supplier must have 1 NPI and 1 or more PTANs related to it in the Medicare system" — separate PTANs typically per medical-group relationship or per MAC. What a PTAN is used for, how it differs from the NPI and the Medicare Beneficiary Identifier, and how to recover a lost one is its own topic — covered in our PTAN guide.

The approval also sets your effective date, and federal regulation gives most 855I filers a limited reach backward. 42 CFR 424.521 permits the listed provider types — the list begins "(i) Physicians. (ii) Non-physician practitioners. (iii) Physician organizations. (iv) Non-physician practitioner organizations." — to "retrospectively bill for services when the provider or supplier has met all program requirements (including State licensure requirements), and services were provided at the enrolled practice location for up to — (i) Thirty days prior to their effective date if circumstances precluded enrollment in advance of providing services to Medicare beneficiaries; or (ii) Ninety days prior to their effective date if a Presidentially-declared disaster" precluded it. Thirty days of retrospective billing is a cushion, not a strategy: a practitioner who starts seeing Medicare patients months before enrolling has unbillable visits no regulation rescues.

On timing expectations, resist the urge to promise a physician a date. The published figures — NGS's 15-day PECOS goal, Novitas's CMS-defined percentile timeframes quoted earlier — are MAC processing goals contingent on a complete application with no development, site visit, or fingerprinting. They are the only timeline numbers worth repeating, and they are not commitments. What you control is the input: a complete, exactly-matching package, and a same-week response to any development request.

Every trigger below is grounded in a requirement printed on the form itself — these are not folklore, they are the form's rules being violated.

• No NPI on the application. CMS's NPI booklet: "An enrolment application without an NPI will be rejected." NPPES assigns the NPI before anything else happens.
• Legal name or TIN that does not match IRS and NPPES records. The form requires the Section 2A/4A identifiers to be "the same Name, SSN, LBN and TIN you used to obtain your NPI," matching "exactly in both PECOS and NPPES." A practice that registered its NPI as "Jane Smith MD PLLC" and applies as "Smith Family Medicine" has built its own development request. Verify against the IRS CP-575, not memory.
• Name, date of birth, or SSN that does not match the social security record in Section 2A.
• A handwritten paper form. "This form must be typed. It may not be handwritten."
• The correspondence address pointed at the billing company. Section 2D "cannot be a billing agent or agency's address or a medical management company address."
• Wrong or missing signatures in Section 15. For a new reassignment, both 15B (practitioner) and 15C (the group's Authorized Official (AO) or delegated official) must be signed; a missing counterpart signature stalls the whole package.
• Missing Section 12 supporting documentation, or an EFT agreement submitted without the voided check or bank letter the form's tips call for.
• Two primary specialties on one application. The form requires "a separate CMS-855I application for each primary specialty."
• A reassignment to a not-yet-enrolled group. Both parties must be enrolled or concurrently enrolling — the 855B and 855I need to travel together for a new group.
• Blowing the 30-day development window under 42 CFR 424.525, which can turn a fixable request into a rejection and a restart.

None of these is exotic, which is the point: 855I outcomes are mostly determined before submission, by whether the identifiers match and the signatures land in the right boxes. That is also the honest pitch for handing it off — not secret access, just process discipline applied to a form that punishes improvisation.