An NCD sets forth the extent to which Medicare will cover specific services, procedures, or technologies on a national basis. Medicare contractors are required to follow NCDs. If an NCD does not specifically exclude/limit an indication or circumstance, or if the item or service is not mentioned at all in an NCD or in a Medicare manual, it is up to the Medicare contractor to make the coverage decision (see LCD). Prior to an NCD taking effect, CMS must first issue a Manual Transmittal, CMS ruling, or Federal Register Notice giving specific directions to our claims-processing contractors. That issuance, which includes an effective date and implementation date, is the NCD. If appropriate, the Agency must also change billing and claims processing systems and issue related instructions to allow for payment. The NCD will be published in the Medicare National Coverage Determinations Manual. An NCD becomes effective as of the date listed in the transmittal that announces the manual revision.