Code of Federal Regulations Title 42. Public Health § 42.424.505 Basic enrollment requirement

To receive payment for covered Medicare items or services from either Medicare (in the case of an assigned claim) or a Medicare beneficiary (in the case of an unassigned claim), a provider or supplier must be enrolled in the Medicare program. Except for those suppliers that complete the CMS–855O form or CMS–identified equivalent, successor form or process for the sole purpose of obtaining eligibility to order or certify Medicare-covered items and services;  once enrolled the provider or supplier receives billing privileges and is issued a valid billing number effective for the date a claim was submitted for an item that was furnished or a service that was rendered. (See 45 CFR part 162 for information on the National Provider Identifier and its use as the Medicare billing number.)