The CMS 855i — formally called the Medicare Enrollment Application for Physicians and Non-Physician Practitioners — is the gateway to billing Medicare Part B. Without a completed and approved CMS 855i application, you cannot receive Medicare reimbursement, and most commercial payers use your Medicare enrollment status as a baseline for their own credentialing decisions. One wrong checkbox in the wrong section can delay your billing privileges by 90 days. This guide walks through every critical section, compares PECOS vs. paper submission, and covers the exact mistakes that trigger rejection.
The CMS 855i form is the Medicare enrollment application for individual practitioners. Submit it through PECOS (45–60 day processing) or by paper to your MAC (90–120 days). You need a Type 1 NPI, taxonomy codes matching NPPES, your IRS EIN letter, and the CMS-588 EFT form (voided check required). Download the current form 855i PDF from CMS.gov — outdated versions are rejected automatically.
What Is the CMS 855i Form?
The CMS 855i form (also written as CMS-855I or simply 855i) is the official Medicare enrollment application for individual healthcare providers. It is used by physicians, nurse practitioners, physician assistants, clinical social workers, and other non-physician practitioners (NPPs) to establish Medicare Part B billing privileges.
The 855i serves two distinct purposes depending on your practice structure:
- Sole proprietor enrollment: You’re billing Medicare directly under your individual Type 1 NPI — Medicare pays you directly
- Benefit reassignment: You’re joining a group practice and want Medicare to pay the group instead of you — completed in Section 4R of the form
Without an approved CMS 855i application, you cannot bill Medicare for any services — even if the patient has active Medicare coverage. Many commercial payers also require Medicare enrollment as a prerequisite before they’ll credential you, making the 855i foundational to your entire payer network. If you want expert help with the process, our Medicare enrollment guide covers the full process, or you can use professional credentialing services to handle it for you.
Medicare Forms 855i vs. 855B: Which Version Do You Need?
CMS offers several Medicare forms 855 for different enrollment scenarios. Choosing the wrong form wastes months — your application will be rejected and you must start over.
| Form | Who Uses It | Common Examples |
|---|---|---|
| CMS 855i This Guide | Individual physicians and NPPs enrolling solo or reassigning benefits to a group | MD, DO, NP, PA, LCSW, psychologist joining or starting a practice |
| CMS-855B | Clinics, group practices, and non-individual Medicare suppliers enrolling as entities | Multi-provider clinic, ambulatory surgery center, FQHC |
| CMS-855S | Suppliers of Durable Medical Equipment, Prosthetics, Orthotics, and Supplies (DMEPOS) | DME supplier, orthotics provider, home health equipment company |
| CMS-855O | Ordering and referring providers who don’t bill Medicare directly but whose orders must be validated | Provider who orders tests but refers billing to a facility |
Prerequisites Before Starting the CMS 855i Application
Do not open the CMS 855i application — in PECOS or on paper — until you have all three of the following secured. Missing any one of them causes an immediate halt.
- Type 1 NPI (Individual): Your personal National Provider Identifier is required. If you also have a Type 2 (organizational) NPI, have that number ready too — you’ll need it for Section 4R if reassigning benefits to a group
- NPPES taxonomy codes: Your specialty taxonomy code in the NPPES registry must match the specialty you’re claiming on the 855i exactly — a mismatch triggers a manual review that can add 30–60 days
- IRS CP-575 EIN letter: The official IRS document showing your Employer Identification Number (EIN) exactly as registered. CMS validates your EIN against IRS records — a single character difference causes rejection
CMS 855i Application: PECOS vs. Paper Submission
Before filling out a single field of your CMS 855i application, choose your submission route. PECOS is the right choice for 95% of providers.
PECOS (Digital) Recommended
Paper Form 855i PDF
How to Complete the Medicare Enrollment Application CMS 855i — Section by Section
The medicare enrollment application CMS 855i is 30+ pages, but 80% of errors and rejections happen in these specific sections. Each one has a specific trap that catches providers off guard.
Section 1 — Reason for Application
Select exactly one: Initial Enrollment (new to Medicare), Reactivation (previously enrolled but deactivated), or Change of Information (updating address, name, etc.). Selecting the wrong reason routes your application to the wrong review team — it will be returned without review.
Section 2 — Personal Identifying Information
Use your full legal name exactly as it appears on your Social Security card — not your professional name or preferred name. “Robert James Smith Jr.” is not the same as “Bob Smith” in CMS’s system. A name mismatch between Section 2 and the IRS database triggers automatic rejection. This is the #1 cause of 855i rejections.
Section 3 — Final Adverse Legal Actions
Disclose all felony convictions, license revocations, suspensions, and exclusions from federal or state health programs. Medicare cross-checks the OIG Exclusion List automatically. Failing to disclose a known action is classified as “False Information” and can result in a 1–3 year ban from reapplying — worse than the original issue.
Section 4 — Practice Location(s)
List every physical location where you see patients. Mobile providers (home visits, assisted living) must still list a “Base of Operations” where records are kept — typically your home office address. Never list a P.O. Box as a practice location — this triggers an automatic request for additional documentation and resets your timeline.
Section 4R — Reassignment of Benefits (Group Practice)
If joining a group practice, use this section to reassign Medicare payments from yourself to the group’s Type 2 NPI. Without this, Medicare mails reimbursement checks to your home address, creating a billing and tax accounting nightmare for both you and the group. Confirm the group’s exact legal name and Type 2 NPI before completing this section.
The CMS-588 EFT Form: Required with Every 855i Submission
The CMS 855i application is incomplete without the CMS-588 Electronic Funds Transfer (EFT) Authorization Agreement. Medicare no longer issues paper checks — your bank account must be on file before your enrollment can be activated.
- Attach a voided check or a bank confirmation letter on official bank letterhead — a screenshot of your banking app is not accepted
- The account holder name on the bank document must exactly match the legal name on the 855i — a single-word difference causes rejection
- For group practices, the bank account must be in the group’s legal business name, not an individual provider’s name
- The CMS-588 is a separate form from the 855i — download it from CMS.gov alongside your form 855i PDF
Top CMS 855i Application Rejection Reasons (and How to Avoid Them)
❌ Name Mismatch
Using “Dan” instead of “Daniel,” omitting “Jr.,” or using a maiden name that differs from your SSN card. Must match IRS and NPPES records exactly.
❌ Outdated Form Version
Submitting an older form 855i PDF version. MACs reject outdated forms automatically — always download fresh from CMS.gov.
❌ Missing Wet Signature (Paper)
Paper submissions require an original blue-ink signature. Stamped, photocopied, or digital signatures on paper forms are invalid and rejected immediately.
❌ Missing or Mismatched EFT
Submitting the 855i without the CMS-588, or with a bank account name that doesn’t match the legal name on the enrollment application.
❌ Taxonomy Code Mismatch
The specialty taxonomy on the 855i must exactly match what’s registered in NPPES. Verify at nppes.cms.hhs.gov before submitting.
❌ Undisclosed Adverse Action
Omitting a past malpractice settlement, license restriction, or OIG exclusion. CMS runs automatic checks — omissions become grounds for a multi-year reapplication ban.
CMS 855i Processing Timeline by Submission Method
| Stage | PECOS (Digital) | Paper Form 855i |
|---|---|---|
| Completeness review | 1–2 weeks (automated) | 2–4 weeks (manual MAC review) |
| Primary source verification | 2–4 weeks | 3–6 weeks |
| Site visit (if required) | 2–4 weeks additional | 2–4 weeks additional |
| Approval & activation | 1–2 weeks | 1–2 weeks |
| Total estimate | 45–60 days | 90–120 days |
Medicare Forms 855i: Revalidation Every 5 Years
Medicare enrollment is not a one-time event. CMS requires all enrolled providers to revalidate their enrollment every 5 years using the same medicare forms 855 process (or through PECOS). Missing a revalidation notice results in automatic deactivation of your Medicare billing privileges — and all Medicare payments stop until revalidation is complete.
- CMS sends revalidation notices by mail and email — check both and ensure your address in PECOS is current
- Respond within the deadline stated in the notice — there is no grace period for late revalidation
- Check your revalidation due date anytime by logging into PECOS at pecos.cms.hhs.gov
- Keep your NPPES taxonomy codes, practice address, and EIN current throughout the 5-year cycle — mid-cycle changes require a separate Change of Information submission
- If you miss a revalidation and billing is deactivated, you must file a Reactivation application (Section 1, Option B on the 855i) — not a new initial enrollment
Related Medicare Enrollment and Credentialing Guides
- How to apply for an NPI number — step-by-step guide
- Insurance credentialing services — get in-network faster
- Aetna credentialing guide 2026
- UnitedHealthcare credentialing guide 2026
- CAQH ProView — the universal credentialing profile
Frequently Asked Questions
What is the CMS 855i form?
The CMS 855i form (CMS-855I) is the official Medicare enrollment application for individual physicians and non-physician practitioners. It establishes your Medicare Part B billing privileges either as a sole proprietor billing Medicare directly, or as an individual joining a group practice and reassigning your Medicare benefits to that group. Without an approved 855i, you cannot receive Medicare reimbursement.
What is the difference between Medicare forms 855i and 855B?
The Medicare form 855i is for individual practitioners — physicians, nurse practitioners, PAs, clinical social workers, and other NPPs. The CMS-855B is for clinics, group practices, and organizational Medicare suppliers enrolling as an entity. When an individual joins a group, both forms are often needed — the individual files the 855i to reassign benefits, and the group already has (or files) the 855B for its entity enrollment.
How do I complete the CMS 855i application?
To complete the CMS 855i application: (1) Gather your Type 1 NPI, matching taxonomy codes in NPPES, and IRS EIN letter before starting. (2) Choose PECOS for 45–60 day processing or paper for 90–120 days. (3) Complete Section 1 (reason for applying), Section 2 (exact legal name from your SSN card), Section 3 (adverse legal history), Section 4 (all practice locations), and Section 4R (benefit reassignment to a group, if applicable). (4) Submit with the CMS-588 EFT form and a voided check attached.
How long does CMS 855i processing take?
PECOS submissions of the CMS 855i application typically process in 45–60 days. Paper form 855i submissions sent to your MAC take 90–120 days. Timelines vary by MAC jurisdiction — Novitas, Palmetto, and NGS each have different average processing speeds. Incomplete applications or missing documents restart the clock from zero.
Where can I download the form 855i PDF?
Download the current form 855i PDF directly from CMS.gov — navigate to the CMS Forms page and search “CMS-855I.” Always use the CMS direct source, never third-party copies. The current form version date appears in the bottom-left corner of page 1. MACs reject outdated form 855i versions automatically. For most providers, submitting through PECOS at pecos.cms.hhs.gov eliminates PDF version concerns entirely.
Can I bill Medicare while my 855i application is pending?
Medicare allows retroactive billing for services rendered up to 30 days before the date your completed application was received by your MAC. Document this date carefully — it determines your earliest billable date. Do not hold claims longer than 12 months from the service date or they will exceed Medicare’s timely filing limit and cannot be collected.
Free Credentialing With Medical Billing From $499 / month
Let us handle your Medicare enrollment and insurance credentialing so you can focus on patients — not paperwork.
