LZS8WSLPparts list

Section 911 of the Medicare Prescription Drug Improvement, and Modernization Act (MMA) of 2003 directed CMS to replace the Part A Fiscal Intermediaries (FIs) and Part B carriers with MACs.  CMS procures all MAC contracts according to the Federal Acquisition Regulation.  Various elements of the Agency’s original strategy for implementing Section 911 of the MMA evolved over the years.  Learn more about the strategy in the Archives.

A Medicare Administrative Contractor (MAC) is a private health care insurer that has been awarded a geographic jurisdiction to process Medicare Part A and Part B (A/B) medical claims or Durable Medical Equipment (DME) claims for Medicare Fee-For-Service (FFS) beneficiaries.  CMS relies on a network of MACs to serve as the primary operational contact between the Medicare FFS program and the health care providers enrolled in the program.  MACs are multi-state, regional contractors responsible for administering both Medicare Part A and Medicare Part B claims.  MACs perform many activities including:

ElkayLZS8WSLPfilter replacement

The DME MACs process Medicare Durable Medical Equipment, Orthotics, and Prosthetics (DMEPOS) claims for a defined geographic area or "jurisdiction", servicing suppliers of DMEPOS.  Learn more about DME MACs at Who are the MACs.

ElkayLZS8WSLPfilter reset

A/B MACs process Medicare Part A and Medicare Part B claims for a defined geographic area or “jurisdiction,” servicing institutional providers, physicians, practitioners, and suppliers.  Learn more about A/B MACs at Who are the MACs.

LZS8WSLPmanual

Official websites use .govA .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPSA lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Currently there are 12 A/B MACs and 4 DME MACs in the program that process Medicare FFS claims for nearly 51% of the total Medicare beneficiary population, approximately 34 million Medicare FFS beneficiaries.  In Fiscal Year 2023 (FY2023), the MACs served more than 1.2 million health care providers who are enrolled in the Medicare FFS program.  Collectively in FY2023, the MACs processed more than 1.1 billion Medicare FFS claims, comprised of approximately 192 million Part A claims and 950 million Part B claims, and paid out approximately $431.5 billion in Medicare FFS benefits.

There are four A/B MACs that process home health and hospice claims in addition to their typical Medicare Part A and Part B claims.  Please note that the four HH+H areas do not coincide with the jurisdictional areas covered by these four A/B MACs.  Learn more about HH+H areas and the MACs responsible for them at Who are the MACs.

MACs work with multiple functional contractors to administer the full FFS operational environment.  Learn more about the relationships between the MACs and the functional contractors by viewing the diagram of MACs: The Hub of the Medicare FFS Program (PDF) and reading about what the functional contractors do at Functional Contractors Overview (PDF).