A Medicare Administrative Contractor (MAC) is a private company CMS contracts to process Medicare Part A and Part B claims within a geographic jurisdiction. The MAC also issues Local Coverage Determinations (LCDs) for its region and decides the first level of Medicare appeal (the redetermination).
What a MAC does
- Processes and pays Medicare fee-for-service claims for its jurisdiction.
- Issues and maintains LCDs that govern local coverage.
- Conducts the first appeal level — the redetermination.
Why the jurisdiction matters
Because each MAC sets its own LCDs, the coverage criteria for the same service can differ by region. The MAC that applies depends on the provider's state — which is why a medical-necessity appeal should cite the LCD for the right jurisdiction.
Frequently asked
Does my MAC affect what Medicare covers?
Who decides my first Medicare appeal?
Primary sources: CMS — Medicare Administrative Contractors (MACs). General information, not legal or medical advice — confirm against the governing rule for the plan type.
Related guides
When the appeal has to be written, and cited
Upload the denied EOB and Merits returns a complete, citation-verified appeal letter — the clinical argument, the payer's own coverage criteria, and your federal appeal rights — in about a minute.