What Is MAC (Medicare Administrative Contractor)?
A Medicare Administrative Contractor is a private organization that contracts with CMS to process Medicare Part A and Part B claims (or DME claims) within a defined geographic jurisdiction, applying CMS coverage rules and publishing local coverage determinations.
- Identify your A/B MAC and DME MAC from the CMS jurisdiction locator rather than from memory or a vendor list, and re-check it whenever a contract is recompeted.
- Monitor that MAC's website for LCD updates and provider bulletins.
- Use the MAC's portal for claim status, redetermination filing, and overpayment and recoupment management.
MAC (Medicare Administrative Contractor)
Also known as: Medicare Administrative Contractor; Part A/B MAC; DME MAC
A Medicare Administrative Contractor is a private organization that contracts with CMS to process Medicare Part A and Part B claims (or DME claims) within a defined geographic jurisdiction, applying CMS coverage rules and publishing local coverage determinations.
Definition
CMS divides Medicare fee-for-service claim processing into 12 A/B MAC jurisdictions and 4 DME MAC jurisdictions, each awarded by contract to a private company (CMS, What's a MAC, read 17 September 2026). Which company holds a given jurisdiction is a contract award that changes when CMS recompetes it, so the current assignment is whatever CMS publishes rather than anything a billing reference can hard-code: the Who are the MACs jurisdiction locator gives the contractor, the states covered and an anticipated contract end date for each A/B and DME jurisdiction. CMS describes the MAC's work as processing FFS claims and accounting for FFS payments, enrolling providers in Medicare FFS, handling provider reimbursement services and auditing institutional cost reports, handling redetermination requests (the first stage of the appeals process), responding to provider inquiries, educating providers on FFS billing requirements, establishing Local Coverage Determinations (LCDs), and reviewing medical records for selected claims.
Example
Checked against the CMS jurisdiction pages on 17 September 2026. A Medicare Part B claim for a Florida patient routes to the A/B MAC for Jurisdiction N, which CMS lists as First Coast Service Options; JN also covers Puerto Rico and the U.S. Virgin Islands. The same patient seen in California routes to Jurisdiction E, listed as Noridian Healthcare Solutions, which also covers Hawaii, Nevada, Guam, American Samoa and the Northern Mariana Islands. If the claim is denied, the redetermination goes to the MAC that made the initial determination, and CMS allows the appellant 120 days from the date of receipt of the initial claim determination to file, with the MAC generally issuing its decision within 60 days of receiving the request (CMS, first level of appeal). Re-confirm the contractor on the CMS jurisdiction page before relying on either assignment.
Common Misconceptions
MACs are not CMS — they are private companies working under CMS contract. There is no fixed rotation interval either: MACRA section 509 extended the maximum MAC contract term, inclusive of all option and renewal periods, from five years to ten, and CMS has said it recompetes on a first-in, first-out basis, oldest award first, spacing re-procurements roughly five months apart rather than running a set cycle per jurisdiction. Each jurisdiction's CMS page carries its own anticipated contract end date, which is the figure to check. Each MAC also publishes its own LCDs, so a service covered in one jurisdiction may carry different documentation requirements in another.
Practical Application
Identify your A/B MAC and DME MAC from the CMS jurisdiction locator rather than from memory or a vendor list, and re-check it whenever a contract is recompeted. Monitor that MAC's website for LCD updates and provider bulletins. Use the MAC's portal for claim status, redetermination filing, and overpayment and recoupment management.
Related Terms
CMS
CMS is the federal agency within the U.S. Department of Health and Human Services that administers Medicare, jointly administers Medicaid and CHIP with the states, and oversees the Health Insurance Marketplaces and HIPAA administrative simplification.
Read definitionMedicare Part A/B/C/D
Medicare is divided into four parts: Part A (hospital insurance) covers inpatient hospital, inpatient SNF, hospice and some home health services; Part B (medical insurance) covers physician services, outpatient care, durable medical equipment, lab and X-ray and many preventive services, and home health services as well; Part C (Medicare Advantage) is private plans that provide all Part A and Part B services; Part D covers outpatient prescription drugs.
Read definitionLCD / NCD (Local & National Coverage Determinations)
An NCD is a nationwide CMS coverage policy specifying whether Medicare will cover a service; an LCD is a coverage policy issued by a Medicare Administrative Contractor (MAC) for its jurisdiction when no NCD applies, defining medical necessity criteria and covered diagnosis codes.
Read definitionWhere This Applies on MedPrecision
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