Medicare Administrative Contractors (MACs)
A Medicare Administrative Contractor (MAC) is a private organization that the Centers for Medicare & Medicaid Services (CMS) awards a contract to administer Fee-for-Service (Original) Medicare claims for a defined geographic jurisdiction. Rather than operating claims offices itself, CMS uses MACs as the operational front door for most day-to-day interactions between providers and Original Medicare: they receive and adjudicate claims, issue payments and remittance advice, handle provider enrollment for their region, and publish local coverage policy. Because each jurisdiction is served by one MAC, the specific contractor assigned to a provider's location determines where claims are sent and which local rules apply. This structure applies to Original Medicare only; Medicare Advantage (Part C) plans are administered by private insurers rather than MACs. Jurisdiction assignments, contractor names, and local policies change over time, so authoritative details should always be confirmed with CMS.
Updated 6 min read
Reviewed by Anwaar Tayyab
Director of Billing Operations ·
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Key takeaways
- MACs are CMS-contracted private companies that process Fee-for-Service Medicare claims within assigned geographic jurisdictions; they do not administer Medicare Advantage plans.
- There are distinct contract types, including Part A/B MACs (also called A/B MACs) and Durable Medical Equipment MACs (DME MACs), and jurisdiction lines determine which contractor a provider works with.
- MACs handle claim adjudication, provider enrollment for their region, appeals at the first level, and the development of local coverage determinations (LCDs).
- The servicing MAC influences local coverage policy, remittance detail, and enrollment processing, so provider workflows are shaped by jurisdiction.
- MAC assignments, names, and jurisdiction boundaries change through CMS re-competes and consolidations, so current details must be verified with CMS.
What a MAC is and where it sits in Medicare
CMS is the federal agency responsible for the Medicare program, but it contracts much of the operational claims workload to regional private companies. A MAC is one of those contractors. Under the framework established by federal Medicare contracting reform, CMS competitively awards MAC contracts to administer Original Medicare within defined jurisdictions. Providers that furnish services to beneficiaries with Original Medicare generally interact with a MAC rather than with CMS directly for routine claims and enrollment.
It is important to distinguish Original Medicare from Medicare Advantage. MACs administer Fee-for-Service Medicare, which includes Part A billing and Part B billing. Medicare Advantage plans, by contrast, are offered by private insurers that handle their own claims and rules, so the MAC framework described here does not govern those plans.
Jurisdiction determines the servicing MAC
What MACs do
MACs carry out a broad set of operational functions on behalf of CMS. While the exact scope is set by each contract, common responsibilities span the claim lifecycle from enrollment through payment and first-level appeals.
- Processing and adjudicating Fee-for-Service claims submitted on the applicable professional or institutional formats, such as the CMS-1500 and UB-04.
- Issuing payments and remittance advice to providers, and beneficiary-facing notices.
- Processing regional provider enrollment and billing privileges applications submitted through CMS systems.
- Developing and publishing local coverage determinations (LCDs) and related articles for their jurisdiction.
- Handling the first level of the Medicare appeals process (redetermination) and provider education and outreach.
- Supporting program integrity activities, including identification and recovery of overpayments.
Because MACs publish local policy and issue remittance detail, the servicing contractor directly affects how coverage decisions and denial reasons appear in practice. Specific edits, policy positions, and documentation expectations vary by contractor and change over time.
Contract types and jurisdictions
CMS organizes MAC work into contract types and geographic jurisdictions. The number of jurisdictions, their boundaries, and the assigned contractors are set and periodically revised by CMS, so the following describes structure rather than a fixed list.
- A/B MAC
- A contractor that processes both Part A (institutional) and Part B (professional) Fee-for-Service claims for a geographic jurisdiction. A/B MACs also handle regional enrollment and local coverage policy.
- DME MAC
- A contractor that processes claims for durable medical equipment, prosthetics, orthotics, and supplies for a multi-state region. The region is fixed by where the beneficiary receiving the item resides, not by where the supplier is located. Whether an item belongs in that stream at all is a benefit-definition question, answered by what makes an item durable medical equipment.
- Home Health & Hospice work
- Certain A/B MACs are designated to process home health and hospice claims for defined regions in addition to their other responsibilities.
Jurisdiction assignments change
Why the servicing MAC matters to providers
For billing operations, the servicing MAC is more than a mailing address. It shapes several concrete parts of the revenue cycle, from enrollment through payment and appeals.
Enrollment routing
Provider enrollment applications submitted through PECOS and the CMS-855 application family are processed by the MAC serving the relevant jurisdiction, which affects where questions and development requests originate.Claim submission and adjudication
Claims are routed to the assigned MAC, which applies national rules and its own local edits during submission and processing. Local coverage policy can influence whether a service is considered supported.Local coverage policy
LCDs and related articles from the servicing MAC set jurisdiction-specific expectations tied to medical necessity, which can differ from another jurisdiction's policy for a comparable service.Remittance and appeals
The MAC issues the remittance advice that explains payment and adjustments, and it decides the first level of appeal when a provider disputes a denial.
Other Original Medicare rules interact with the MAC as well. Situations involving Medicare Secondary Payer and timely filing are administered through the servicing contractor, and the applicable Medicare fee schedules are applied during adjudication. Precise rates, filing windows, and coordination requirements vary and should be confirmed with authoritative CMS sources.
Frequently asked questions
Do MACs process Medicare Advantage claims?
No. MACs administer Fee-for-Service (Original) Medicare only. Medicare Advantage (Part C) plans are offered by private insurers that process their own claims and set their own rules, so the MAC framework does not apply to them. Providers should confirm plan type before assuming which entity handles a claim.
How does a provider know which MAC serves them?
MAC assignment is generally determined by geographic jurisdiction and, for certain items, by service type or the beneficiary's residence. Because CMS periodically revises jurisdictions and re-competes contracts, the current contractor and boundaries should be verified directly through CMS rather than assumed from prior experience.
What is the difference between an A/B MAC and a DME MAC?
An A/B MAC processes Part A institutional and Part B professional claims for a geographic jurisdiction and handles regional enrollment and local policy. A DME MAC processes claims for durable medical equipment, prosthetics, orthotics, and supplies across a multi-state region, and the region is determined by where the beneficiary receiving the item resides rather than by the supplier's location.
Do MACs create their own coverage rules?
MACs develop local coverage determinations (LCDs) and related articles for their jurisdictions, which can create jurisdiction-specific expectations. These operate alongside national coverage policy set by CMS. Because local policy differs by contractor and changes over time, the current LCDs for a jurisdiction should be checked directly.
Which appeal level do MACs handle?
The servicing MAC decides the first level of the Medicare appeals process, known as redetermination, when a provider disputes an initial claim determination. Later appeal levels are handled by other entities. Filing requirements and deadlines are set by CMS and should be confirmed with authoritative sources.
Related glossary terms
Key terms that appear throughout Medicare Administrative Contractor workflows and Original Medicare billing.
Related reading
Continue with closely connected topics in the Medicare billing cluster.
How Medicare is structured (Parts A, B, C, D)
Understand where Original Medicare and Medicare Advantage sit before mapping MAC responsibilities.
National and local coverage determinations
See how MAC-published LCDs relate to national coverage policy in day-to-day billing.
Medicare enrollment and billing privileges
Learn how MACs process regional enrollment applications and billing privileges.
Reading the Medicare remittance and MSN
Interpret the payment and adjustment detail that the servicing MAC issues.
Medicare fee schedules explained
Review how the fee schedules a MAC applies during adjudication are structured.
Authoritative sources
- 42 U.S.C. § 1395kk-1 — Contracts with medicare administrative contractors (opens in a new tab)
United States Code, 2023 Edition (GPO). The statute that creates the MAC. It permits the Secretary to contract with an eligible entity to serve as a medicare administrative contractor, defines the term as an agency, organization, or other person with a contract under the section, and lists the functions a contract may cover — determining payment amounts, making payments, beneficiary education and assistance, provider consultative services, communication with providers, provider education and technical assistance, an improper payment outreach and education program, and, expressly, developing local coverage determinations. Subsection (b)(1) requires competitive procedures, permits term-to-term renewal without further competition where the contractor has met or exceeded its performance requirements, subject to a floor requiring competitive procedures at least once every 10 years, and lets the Secretary transfer functions among contractors on public notice — the mechanism behind jurisdiction reassignment.
- What's a MAC (opens in a new tab)
Centers for Medicare & Medicaid Services. CMS's own description of the contractor: a private health care insurer awarded a geographic jurisdiction to process Medicare Part A and Part B or DME claims for Fee-for-Service beneficiaries, serving as the primary operational contact between the Medicare FFS program and enrolled providers. Lists what MACs do, including processing FFS claims, making and accounting for payments, enrolling providers, handling redetermination requests as the first stage of the appeals process, responding to and educating providers, and establishing local coverage determinations. Records that Section 911 of the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 directed CMS to replace the Part A fiscal intermediaries and Part B carriers with MACs, that CMS procures MAC contracts under the Federal Acquisition Regulation, and that four A/B MACs also process home health and hospice claims for areas that do not coincide with those MACs' own A/B jurisdictions.
- 42 CFR 421.404 — Assignment of providers and suppliers to MACs (opens in a new tab)
eCFR. The rule that decides which MAC a given biller deals with. Providers enroll with and are paid by the MAC contracted to administer claims for the Medicare benefit category applicable to their covered services in the geographic locale where the provider is physically located; suppliers other than DMEPOS suppliers use the MAC for the locale in which they furnished the services; and suppliers of DMEPOS are paid by the MAC assigned to administer DMEPOS claims for the regional area in which the beneficiary receiving the DMEPOS resides. The section also sets the narrow exceptions CMS may grant, including qualified chain providers permitted to bill from their home office locale.
- 42 CFR 405.904 — Medicare initial determinations, redeterminations and appeals: General description (opens in a new tab)
eCFR. Sets out the Fee-for-Service claim appeal ladder. The Medicare contractor makes the initial determination when a Part A or Part B claim is submitted; a dissatisfied party may ask that same contractor to perform a redetermination; and only after that does a Qualified Independent Contractor perform the reconsideration, followed by a hearing before an ALJ, review by the Medicare Appeals Council, and suit in federal district court. This is the provision establishing that the MAC decides the first level and other entities decide the rest.
- 42 CFR 405.921 — Notice of initial determination (opens in a new tab)
eCFR. Establishes the notices a Medicare contractor issues once it decides a claim. Under paragraph (b)(1), an electronic or paper remittance advice is itself the notice of initial determination sent to providers and suppliers that accept assignment. Paragraph (b)(2) requires that notice to carry the basis for any full or partial denial of services or items on the claim, the right to a redetermination, all applicable claim adjustment reason and remark codes to explain the determination, and the source of the remittance advice. Paragraph (a) sets the parallel written notice sent to the beneficiary, which must give the reasons for the determination, including whether a local coverage determination or national coverage determination was applied, and instructions for requesting a redetermination.