The CMS Parts C & D Appeals Guidance: the operative rulebook

42 CFR Part 422 sets the legal minimum — what a plan MUST do. The guidance document fills in the operational specifics CMS expects plans to follow to actually comply: what a notice letter has to contain, how a physician-reviewer requirement is documented, what "good cause" for a late filing typically looks like.

When a citation on a CaseWhy Appeals page references "CMS Guidance §" followed by a section number, that's this document specifically — distinct from a bare "42 CFR §" citation, which points to the regulation text itself.

Because this guidance is CMS's own interpretation of the regulation (not the regulation itself), a plan that follows the guidance is following CMS's own expectations for compliance — which makes it a strong, specific standard to hold a plan to in an appeal, on top of the underlying regulation.

This guidance document also covers grievances — complaints about the plan's conduct or quality of service, as distinct from a coverage decision — and organization-determination timeframes, giving one place CMS itself intends plans to look for the complete operational picture of how each process should run.

The guidance is publicly available on CMS's own website, meaning a family (or an appeal letter) can cite it directly by section number, the same way this site does — it isn't an internal-only document restricted to plans and contractors.

Plans train their own staff against this document, so a reviewer who sees it cited accurately in an appeal letter recognizes it as the same standard their own training covers, not an outside or unfamiliar source.