Guide

Your MAC: who it is and why its manuals control

Summary

Your Medicare Administrative Contractor is the private company CMS pays to process Part A and B claims for your jurisdiction, and it is determined by where you furnish services, not where the patient lives. CMS publishes a directory of which MAC serves each state and region. Its manuals matter because national rules set the floor, but your MAC issues the local coverage determinations and billing articles your specific claims are adjudicated against.

By Gale Editorial · Updated 2026-07-26. Every figure cited to a dated source. How we write.

What a MAC is and how yours is determined

A Medicare Administrative Contractor — a MAC — is a private company CMS contracts to process Medicare Part A and Part B claims for a defined geographic jurisdiction. It receives your claims, adjudicates them, issues your remittances, handles enrollment, and runs first-level appeals for its region. Which MAC is yours is set by where you furnish services — for an office-based solo, your practice location — not by where your patient lives. CMS publishes a directory of the MACs and the jurisdiction each one serves, and that directory is the authoritative answer to which contractor is yours 1Ref 1Centers for Medicare & Medicaid Services (2026).Medicare Administrative Contractors.That Medicare claims administration is regionalized across MACs, that a provider's MAC is set by where services are furnished, and that CMS publishes a directory of which MAC serves each jurisdiction..

The short version: there is no single national claims office. Medicare's day-to-day administration is regionalized, and you belong to exactly one A/B MAC. Knowing which one is the first step to knowing which rules actually bind your claims.

Why your MAC's manuals control your claims

National Medicare rules apply everywhere. The program's Internet-Only Manuals and national coverage determinations set requirements that hold in every jurisdiction, and they are the operative national instruction 2Ref 2Centers for Medicare & Medicaid Services (2026).Internet-Only Manuals (IOMs).That national Medicare program instructions live in the CMS Internet-Only Manuals and apply across all MAC jurisdictions — the national floor beneath each MAC's local policy.. But those national rules are a floor, not the whole rulebook. Your MAC issues its own local coverage determinations and billing articles for its region, and it is your MAC that measures your claims against them.

That is why two clinicians in different states can face different documentation requirements for the same code: a local coverage determination can specify which diagnoses support a service and what the record must show, and those specifics vary by contractor. National and local coverage rules both live in the Medicare Coverage Database, searchable by code 3Ref 3Centers for Medicare & Medicaid Services (2026).Medicare Coverage Database (MCD) Search.That national coverage determinations and each MAC's local coverage determinations and articles are searchable together in the Medicare Coverage Database, with the documentation each service requires.. When both apply, you satisfy the national rule and then meet your MAC's local detail on top of it — the local layer is where most avoidable denials are decided, which is why an unexpected denial or an ABN question so often traces back to an LCD you had not read.

How to find your MAC

Finding your MAC is a lookup, and it takes a minute. CMS publishes a jurisdiction directory that maps each state and region to its A/B MAC, so you look up your practice location and read off the contractor 1Ref 1Centers for Medicare & Medicaid Services (2026).Medicare Administrative Contractors.That Medicare claims administration is regionalized across MACs, that a provider's MAC is set by where services are furnished, and that CMS publishes a directory of which MAC serves each jurisdiction.. Confirm it against the MAC named in your Medicare enrollment record, since that is the contractor your claims already route through. If you practice across a state line or relocate, check the directory again — your jurisdiction follows the service location.

Your MAC assignment is tied to the same enrollment that governs your participation, non-par, opt-out posture, so the contractor that processes your claims is also the one that processes your participation election and your enrollment changes. Getting the MAC right is not a trivia question; it decides where every form and every appeal goes.

What your MAC publishes that you actually use

Your MAC's provider portal is where the guidance that binds you lives, and it is worth treating as a primary reference rather than a last resort. Each MAC — for example, Novitas Solutions within its jurisdiction 4Ref 4Novitas Solutions Medicare (2026).Novitas Solutions Medicare.That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, signature and documentation guidance, and enrollment workflows on its provider portal — a named contractor example. — publishes its local coverage determinations, billing and coding articles, signature and documentation requirements, and enrollment workflows in one place. The Medicare Coverage Database pulls the coverage determinations together and is searchable by code 3Ref 3Centers for Medicare & Medicaid Services (2026).Medicare Coverage Database (MCD) Search.That national coverage determinations and each MAC's local coverage determinations and articles are searchable together in the Medicare Coverage Database, with the documentation each service requires., but the billing articles and documentation guidance that prevent denials sit on the MAC's own site.

The practical routine is to pull your MAC's LCDs and articles for your top codes once, so you know in advance what the record has to support and when a denial is foreseeable. That is the same reading that tells you when an ABN is warranted, and it is far cheaper to do before the claim than to learn from the remittance.

The contractors, and how a jurisdiction can change

The A/B MAC work is split among a handful of regional contractors — Palmetto GBA and Noridian Healthcare Solutions are two examples alongside Novitas Solutions 5Ref 5Palmetto GBA (2026).Palmetto GBA.That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, and documentation guidance on its provider portal — a named contractor example.6Ref 6Noridian Healthcare Solutions (2026).Noridian Healthcare Solutions — Medicare.That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, and documentation guidance on its provider portal — a named contractor example.4Ref 4Novitas Solutions Medicare (2026).Novitas Solutions Medicare.That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, signature and documentation guidance, and enrollment workflows on its provider portal — a named contractor example. — each serving its own jurisdictions. CMS's directory names the current contractor for every state and region, and that is the list to trust rather than any static roster, because it changes 1Ref 1Centers for Medicare & Medicaid Services (2026).Medicare Administrative Contractors.That Medicare claims administration is regionalized across MACs, that a provider's MAC is set by where services are furnished, and that CMS publishes a directory of which MAC serves each jurisdiction..

It changes because CMS periodically re-competes the MAC contracts. When a contract moves to a new company, the contractor serving your jurisdiction can change even though your practice has not moved an inch. When that happens, CMS and the incoming MAC publish transition notices with new portal addresses, submission details, and effective dates. Watch for those, because your claims routing, your local coverage determinations, and even your remittance format move with the new contractor. A transition you miss shows up as claims sent to the wrong place.

What to do once you know your MAC

Once you have identified your MAC, a few one-time steps turn it into a working reference. Bookmark its provider portal and subscribe to its update list or listserv so policy changes reach you before a denial does. Pull its local coverage determinations and billing articles for your most-billed codes, and note any that add documentation your national reading did not 3Ref 3Centers for Medicare & Medicaid Services (2026).Medicare Coverage Database (MCD) Search.That national coverage determinations and each MAC's local coverage determinations and articles are searchable together in the Medicare Coverage Database, with the documentation each service requires.. Confirm the contractor named in your enrollment record matches the directory 1Ref 1Centers for Medicare & Medicaid Services (2026).Medicare Administrative Contractors.That Medicare claims administration is regionalized across MACs, that a provider's MAC is set by where services are furnished, and that CMS publishes a directory of which MAC serves each jurisdiction.. And if you bill across more than one jurisdiction — a second office, or telehealth to patients seen in another MAC's region — check which contractor each service routes to, because the local coverage rules and the portal you rely on change with the jurisdiction.

From there, the mental model is simple: the national rule is the floor, and your MAC's local guidance is the detail your claims are actually judged on. When national and local guidance both speak to a service, you meet both. And when your MAC's crossovers, edits, or an MSP questionnaire raise a jurisdiction-specific question, the answer is on your MAC's portal, not in a general summary — which is exactly why knowing which MAC is yours is worth the minute it takes.

Common questions

CMS publishes a directory of Medicare Administrative Contractors and the jurisdiction each serves; your MAC is determined by where you furnish services. Look up your state or region in that directory, and confirm it against the contractor named in your enrollment record. Once you know it, bookmark its provider portal — that is where your binding local guidance lives.

National rules — the CMS manuals and national coverage determinations — apply everywhere, but your MAC issues local coverage determinations and billing articles for its jurisdiction and adjudicates your claims against them. Two clinicians in different states can face different documentation requirements for the same code. The national rule is the floor; your MAC's guidance is what your specific claims are measured against.

Yes. CMS periodically re-competes MAC contracts, so the contractor serving your jurisdiction can change even though your practice stays put. When that happens, CMS and the incoming MAC publish transition notices with new portal addresses and submission details. Watch for those, because your claims routing and local guidance move with the new contractor.

No. A national coverage determination applies across all jurisdictions; a local coverage determination is your MAC's own policy for its area, and it can be more specific about which diagnoses and documentation support a service. Both live in the Medicare Coverage Database, searchable by code. When both apply, you meet the national rule and then satisfy your MAC's local detail on top.

On your MAC's provider portal. Each contractor publishes its local coverage determinations, billing articles, signature and documentation guidance, and enrollment workflows there. Search the Medicare Coverage Database for your codes to pull the relevant determinations, and subscribe to your MAC's update list so policy changes reach you before a denial does.

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References

1.Centers for Medicare & Medicaid Services (2026). Medicare Administrative Contractors. Centers for Medicare & Medicaid Services (CMS). link ✓That Medicare claims administration is regionalized across MACs, that a provider's MAC is set by where services are furnished, and that CMS publishes a directory of which MAC serves each jurisdiction.
2.Centers for Medicare & Medicaid Services (2026). Internet-Only Manuals (IOMs). Centers for Medicare & Medicaid Services (CMS). link ✓That national Medicare program instructions live in the CMS Internet-Only Manuals and apply across all MAC jurisdictions — the national floor beneath each MAC's local policy.
3.Centers for Medicare & Medicaid Services (2026). Medicare Coverage Database (MCD) Search. Centers for Medicare & Medicaid Services (CMS). link ✓That national coverage determinations and each MAC's local coverage determinations and articles are searchable together in the Medicare Coverage Database, with the documentation each service requires.
4.Novitas Solutions Medicare (2026). Novitas Solutions Medicare. Medicare Administrative Contractor portal. link ✓That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, signature and documentation guidance, and enrollment workflows on its provider portal — a named contractor example.
5.Palmetto GBA (2026). Palmetto GBA. Medicare Administrative Contractor portal. link ✓That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, and documentation guidance on its provider portal — a named contractor example.
6.Noridian Healthcare Solutions (2026). Noridian Healthcare Solutions — Medicare. Medicare Administrative Contractor portal. link ✓That this Medicare Administrative Contractor publishes its jurisdiction's LCDs, billing articles, and documentation guidance on its provider portal — a named contractor example.

https://www.gale.care/for-providers/mc-mac-who-is-mine · 6 sources. Competitor details are cited to dated public sources and maintained as they change; figures are estimates, not commitments. Synthetic demonstration.

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