The CMS 855I Medicare enrollment application is the form individual physicians and non-physician practitioners use to obtain a Medicare billing number. You can file it electronically through the Provider Enrollment, Chain, and Ownership System (PECOS) or mail a paper version to your Medicare Administrative Contractor (MAC). It captures your identity, licenses, practice locations, and any adverse legal history. Online submissions are typically processed in about 30 days; paper submissions take closer to 65.1Centers for Medicare & Medicaid Services. Enrollment and Certification Roadmap for Institutional Providers
Who Files the 855I
Every physician and eligible professional who wants to bill Medicare as an individual practitioner uses this form. The 855I itself states that all physicians and all eligible professionals defined in section 1848(k)(3)(B) of the Social Security Act must use it to enroll and receive a billing number. Non-physician practitioners covered include nurse practitioners, physician assistants, clinical social workers, physical and occupational therapists in private practice, CRNAs, certified nurse midwives, clinical psychologists, audiologists, speech language pathologists, and registered dietitians.2Centers for Medicare & Medicaid Services. CMS-855I Medicare Enrollment Application
You also use the 855I to report changes to an existing enrollment, such as a new practice address or updated license, and to complete revalidation every five years.3Centers for Medicare & Medicaid Services. Revalidations (Renewing Your Enrollment) Organizations and group practices file the 855B instead, and submitting the wrong form is grounds for automatic rejection.4eCFR. 42 CFR 424.525 – Rejection of a Provider’s or Supplier’s Enrollment Application
What to Gather Before You Start
Missing documents are one of the most common reasons applications bounce, and once the MAC issues a development request you have only 30 days to fix the gap before the filing is rejected.5Centers for Medicare & Medicaid Services. Stay of Enrollment Have the following ready before you begin:
A Type 1 (Individual) National Provider Identifier from NPPES.6NPPES. Apply for an NPI A Type 2 NPI is for organizations and will not work here. If you already have a Type 1, confirm the details on file match what you plan to enter, because mismatches cause delays.
Your current state medical license, board certifications, and DEA registration if applicable. Federal regulations at 42 CFR 424.510 require submission of all applicable federal and state licenses and certifications with the enrollment application.7eCFR. 42 CFR 424.510 – Requirements for Enrolling in the Medicare Program You also need your Social Security Number and date of birth for the personal identification fields.
Practice location details for every site where you see Medicare patients: exact street address (no P.O. boxes), phone number, and the address where medical records are stored if different. If you render services in patients’ homes, the form has a dedicated field.
A completed CMS-588 Electronic Funds Transfer authorization, with your bank routing and account numbers.8Centers for Medicare & Medicaid Services. CMS 588 – Electronic Funds Transfer (EFT) Authorization Agreement All enrolling providers must agree to receive Medicare payments by EFT.7eCFR. 42 CFR 424.510 – Requirements for Enrolling in the Medicare Program
Group practice information if applicable: the group’s legal business name and Tax Identification Number for the reassignment section. Joining an already-enrolled group also usually means filing a Form 855R (covered below).
Filling Out the Form
The 855I runs 15 numbered sections, but several are intentionally blank. The active sections that require real decisions are these.
Section 1: Reason for Filing
Check the box that matches what you’re doing: initial enrollment, revalidation, reactivation, change of information, or voluntary termination. If you’re reporting a change, Section 1B asks you to specify what’s changing. Getting this correct at the top routes the application through the right processing track.
Section 2: Personal Identifying Information
The longest section. It collects your legal name, date of birth, SSN, and gender, and then extends into state license and certification numbers with expiration dates (2B), a correspondence mailing address (2D), residency information if applicable (2F), physician specialty (2G), and non-physician specialty type (2H).2Centers for Medicare & Medicaid Services. CMS-855I Medicare Enrollment Application Your name and SSN must match Social Security Administration records exactly. A missing middle initial or a hyphenated name entered differently can trigger a rejection.
Section 3: Final Adverse Legal Actions
Disclose everything, regardless of whether records were expunged or an appeal is pending. Section 3A covers all federal or state felony convictions within the past 10 years, plus certain misdemeanors related to healthcare delivery, patient abuse, fraud, or controlled substances. Section 3B covers any past or current medical license revocation or suspension, OIG exclusion, federal debarment, civil monetary penalty, or Medicaid billing termination. The MAC verifies these against federal databases, and an omission is often more damaging than the underlying event.
Section 4: Business Information
Section 4A captures the legal business name, Tax Identification Number, and organizational type for a private practice. Section 4B lists each practice location with address, phone, hours, and the date you started (or plan to start) seeing patients there. Section 4F handles reassignment: if a group or organization will bill and collect on your behalf, you identify that entity here.
Sections 6, 8, 12, 13
Section 6 covers a managing employee if someone other than you runs day-to-day operations. Section 8 lists any third-party billing agency. Section 12 is a documentation checklist tailored to your provider type. Section 13 is an optional contact person the MAC can call with processing questions, which is useful if you work with a billing service or enrollment specialist.
Sections 5, 7, 9, 10, 11
Intentionally blank. Skip them.
Sections 14 and 15: Certification and Signature
Section 14 lays out the penalties for false information. Section 15 is where you sign and date the certification attesting that everything in the application is accurate. Paper submissions require an original handwritten signature; PECOS uses an electronic signature process.9Centers for Medicare & Medicaid Services. E-Signature How To Guide
How to Submit
Through PECOS
PECOS is the internet-based system that lets you complete, sign, and submit the 855I electronically.10Centers for Medicare & Medicaid Services. Medicare Provider Enrollment, Chain, and Ownership System Because PECOS is paperless, the core application no longer needs to be mailed.11Centers for Medicare & Medicaid Services. Manage Your Enrollment Any supporting documents you don’t upload digitally should be printed and mailed to your MAC along with a copy of the submission confirmation page.9Centers for Medicare & Medicaid Services. E-Signature How To Guide
Using PECOS requires a login through the CMS Identity and Access Management system. Build in extra time for account setup on a first application. PECOS validates fields as you go and flags common data-entry errors before final submission, which is a large part of why online applications process faster.
By Mail
Print the completed 855I, sign it by hand, and mail it to your MAC with the CMS-588 and all supporting documents.12Centers for Medicare & Medicaid Services. Enrollment Applications CMS publishes jurisdiction maps and a state-by-state list to help you identify the correct MAC.13Centers for Medicare & Medicaid Services. Who Are the MACs Keep a copy of the signed form before mailing.
Paper-specific rules: the form cannot be completed in pencil; it cannot be submitted by fax or email; the signature cannot be stamped or photocopied; and if the signature is dated more than 120 days before the MAC receives it, the application is rejected.4eCFR. 42 CFR 424.525 – Rejection of a Provider’s or Supplier’s Enrollment Application
After You Submit
Processing Time
CMS estimates paper applications take approximately 65 days and PECOS submissions approximately 30 days.1Centers for Medicare & Medicaid Services. Enrollment and Certification Roadmap for Institutional Providers These are estimates. Complex applications and high-volume periods at your MAC can push timelines longer.
Development Requests
If the MAC finds missing or incomplete information, it issues a single comprehensive development request. You have 30 days to respond.5Centers for Medicare & Medicaid Services. Stay of Enrollment Miss that window and the application is rejected rather than denied, meaning you start over with a new submission instead of appealing.
Effective Date
For physicians and non-physician practitioners, the effective date of Medicare billing privileges is the later of two dates: the date you filed the application, or the date you first began furnishing services at the practice location listed on the form.14eCFR. 42 CFR 424.520 – Effective Date of Medicare Billing Privileges Services provided to Medicare beneficiaries before your effective date are not reimbursed, so file before you start seeing patients at a new location.
Reassigning Benefits With Form 855R
If you work for a group practice, hospital-based clinic, or other organization that bills Medicare on your behalf, you typically reassign your billing rights to that entity using Form 855R. Both you and the organization must be enrolled in Medicare (or enrolling at the same time) for the reassignment to take effect.15Centers for Medicare & Medicaid Services. Processing the CMS-855R Medicare Enrollment Application
A few rules that trip people up: you file a separate 855R for each organization you’re reassigning to; sole owners of a corporation, LLC, or professional association don’t need an 855R to bill through their own entity; physician assistant employment arrangements are reported on the 855I itself rather than the 855R; and establishing a new reassignment requires signatures from both you and an authorized official of the organization, while terminating a reassignment requires only one. You can file the 855R through PECOS or on paper to your MAC.
Common Reasons Applications Get Rejected
42 CFR 424.525 sets out the specific grounds for rejection. Knowing them in advance saves months:4eCFR. 42 CFR 424.525 – Rejection of a Provider’s or Supplier’s Enrollment Application
- Missing required data such as name, SSN, contact information, or practice location details.
- Unsigned or undated form. Both are required.
- Stamped or photocopied signature on a paper submission.
- Signature dated more than 120 days before the MAC receives the application.
- Paper form completed in pencil.
- Wrong form (an 855B submitted in place of the 855I, or vice versa).
- Missing supporting documentation not provided within 30 days of filing.
- Missing certification statement in Section 15 on a paper application.
- Submission by fax or email without specific CMS authorization.
Rejection means the application is treated as though it was never filed, and your effective date resets. That alone justifies checking every field and attachment before you submit.
Revalidation
Medicare enrollment isn’t permanent. Providers and suppliers generally revalidate every five years; DMEPOS suppliers revalidate every three.3Centers for Medicare & Medicaid Services. Revalidations (Renewing Your Enrollment) CMS sends a notice when your cycle approaches, and you can check your due date using the Medicare Revalidation List.16Centers for Medicare & Medicaid Services Data. Medicare Revalidation List Miss the deadline and CMS can hold your reimbursements or deactivate your billing privileges. If you’re deactivated, you resubmit a complete enrollment application, and Medicare will not reimburse services provided during the gap. Treat the deadline as fixed.