CMS-855I

The CMS-855I is how an individual clinician gets a Medicare billing number. Every physician, and every eligible professional defined in section 1848(k)(3)(B) of the Social Security Act, completes it to enroll in Medicare, either on the paper form or through Internet-based PECOS¹. The practitioner needs an NPI first, and the name and Social Security Number on the application must be the same ones used to obtain that NPI, because PECOS and NPPES have to match exactly¹.

First enrollment is only one use. The same form handles revalidation when the MAC sends notice, reactivation of a billing number to resume billing, enrollment with a second MAC after opening a location in its territory, changes such as an added practice location, and voluntary termination. It also carries every reassignment action. CMS discontinued the separate CMS-855R, so adding, changing or ending a reassignment of benefits now goes on the 855I¹. For a new reassignment, the practitioner signs one certification section and the group’s delegated or authorized official signs another¹.

Two mistakes repeat. The first is using the wrong form for the entity. The 855I enrolls the person; a clinic or group practice enrolls itself with the CMS-855B², and a sole owner who wants to add an authorized or delegated official to the enrollment is told to use the 855B rather than the 855I¹. The second is slow follow-up. The MAC can ask for more documentation to validate what you reported, and 42 CFR 424.525 gives you 30 days from the request to provide it¹.