Medicare credentialing is really Medicare enrollment. There is no credentialing committee and no negotiated fee schedule. You either meet the requirements or you do not, and the rate is published. That makes it more predictable than commercial credentialing. It is also less forgiving in one way: an enrollment problem stops payments outright rather than reducing them.
For the work itself, see our medical credentialing services.
Which form applies to you
| Form | Who files it |
|---|---|
| CMS-855I | Individual physicians and non-physician practitioners |
| CMS-855B | Group practices, clinics and most supplier organizations |
| CMS-855A | Institutional providers, hospitals, home health agencies, hospices |
| CMS-855S | DMEPOS suppliers |
| CMS-855R | Reassignment of benefits from an individual to a group |
| CMS-588 | Electronic funds transfer authorization |
The reassignment is the step people forget
A physician joining a group needs the individual enrollment and the CMS-855R reassigning their benefits to that group. Completing the 855I alone leaves the practice unable to bill for them. It is the most common Medicare enrollment error we are asked to unpick. It is usually found only when the claims deny.
PECOS
PECOS is the online system for all of this, and it is faster and easier to track than paper. You need an active NPI in NPPES first. You also need an Identity & Access account linked to it before PECOS will let you file. Access management is genuinely the fiddliest part of the process for most practices.
Effective dates and retrospective billing
Medicare is unusually generous here compared with commercial payers, and providers routinely leave the benefit unused.
- For physicians and most non-physician practitioners, the effective date is the later of two dates. Either the date the contractor received an application it went on to approve, or the date you first provided services at that location.
- There is normally a short retrospective billing window before that effective date. It lets you bill for care you have already given.
- This is why filing early matters even if you are not ready to see patients: the clock starts at receipt of the application, not at approval.
Revalidation: the one that stops payments
Set a calendar reminder the day you enroll
Medicare requires most providers to revalidate their enrollment every five years, and DMEPOS suppliers every three. The contractor sends a notice, but it goes to the address and contact on file, which is frequently an old practice manager's email.
Miss the deadline and your billing privileges are deactivated. Deactivation is not a denial you can appeal on clinical grounds; it is a switch that has been turned off, and reactivating it takes weeks during which nothing pays.
We track revalidation dates for every provider we enroll, because this is entirely preventable and expensive when it is not prevented.
Reporting changes
Certain changes must be reported within 30 days, including a change of ownership, a change of practice location and adverse legal actions. Most other changes are reportable within 90 days. Late reporting of an address change is one of the few administrative faults that can suspend an otherwise healthy enrollment.
Behavioral health: what changed in 2024
Mental health counselors (LPC, LMHC, LPCC) and marriage and family therapists became eligible to enroll in Medicare as independent providers on 1 January 2024. Before that, only psychologists and clinical social workers could bill Medicare directly.
Many therapists who wrote Medicare off years ago have not revisited that decision, and in most markets the panel is wide open as a result. See insurance credentialing for therapists and mental health providers for license-by-license detail.
Medicare Advantage is a different thing entirely
Being enrolled in traditional Medicare does not put you in network with any Medicare Advantage plan. MA plans are commercial contracts with their own credentialing, their own networks and their own fee schedules, and they must be applied for individually. Practices with large Medicare populations often discover this the hard way.
Related
- The work itselfMedical credentialing and provider enrollment services
- NPs and PAsNurse practitioner credentialing the 85% rule and incident-to
Free enrollment check
Tell us your provider type and whether you are joining a group. We will tell you which forms you need, what your likely effective date is, and when your revalidation falls.
Free credentialing check Talk to a credentialing specialist