Who Processes Your Original Medicare Claims and How Long It Takes

Medicare claims processors handle your Original Medicare paperwork, not Medicare itself

Original Medicare claims are not processed by Medicare directly. Instead, private insurance companies called Medicare Administrative Contractors (MACs) handle the paperwork for your region. Medicare sets the rules and pays the bills, but MACs do the actual work of receiving claims from doctors and hospitals, checking them, and sending payment.

There are 12 MACs across the United States, each covering a specific geographic area. Your state may be split between two or three MACs depending on the type of claim — one MAC handles Part A claims (hospital care) and a different one handles Part B claims (doctor visits and outpatient services). When your doctor or hospital submits a claim, it goes to the MAC for your region.

You do not choose your MAC or contact them directly in most cases. Your healthcare provider submits the claim on your behalf. If you need to follow up on a claim status or file an appeal, you will contact the MAC for your area — and knowing which one handles your claim matters, because each MAC has its own phone number and mailing address.

Key Takeaways

Medicare Administrative Contractors (MACs) are private companies that process Original Medicare claims for your region; there are 12 MACs total across the United States.
One MAC processes Part A claims (hospital, skilled nursing, hospice) and a different MAC processes Part B claims (doctor visits, lab work, imaging) for most states.
Your healthcare provider submits claims to the correct MAC automatically, but you can contact your regional MAC to check claim status or file an appeal.
Standard processing time is 30 days from the date the MAC receives a clean claim, though some claims take longer if they need review.
You can find your regional MAC by entering your state and claim type on the official Medicare website or by calling 1-800-MEDICARE.

How to find which MAC handles claims in your state

The easiest way to find your MAC is to call 1-800-MEDICARE (1-800-633-4227) and tell them your state and whether you have a question about a Part A or Part B claim. They will give you the MAC name, phone number, and mailing address for your region.

You can also look it up yourself on the official Medicare website at cms.gov. Go to the "Find Care Providers" section and search for "Medicare Administrative Contractors" or "MAC." The site has a map and a list showing which MAC covers each state for Part A and Part B claims. Some states have one MAC for both; others have separate contractors.

Keep the MAC's contact information in a safe place if you think you will need to follow up on a claim. Write down the phone number, fax number, and mailing address. If you file an appeal or need to request records about a specific claim, you will need to contact the correct MAC — sending a letter to the wrong one will delay your answer.

What happens when your provider submits a claim

When you see a doctor or go to the hospital, the provider's billing office submits a claim to the appropriate MAC within a set timeframe — usually within 30 days of your visit. The claim includes your Medicare number, the date of service, the diagnosis code, the procedure code, and the charge. The MAC receives thousands of claims every day.

The MAC first checks whether the claim is complete and whether the charges follow Medicare rules. If information is missing or the charge seems too high for that service, the MAC may ask the provider for more details before paying. A "clean claim" — one with all required information and no red flags — usually processes within 30 days.

Once the MAC approves the claim, it sends payment to the provider and sends you an Explanation of Benefits (EOB). The EOB shows what the provider charged, what Medicare approved, what Medicare paid, and what you owe (your deductible, coinsurance, or copay). This is not a bill — it is a record of what happened with that claim.

Processing times and what causes delays

Standard processing time is 30 days from the date the MAC receives a complete claim. However, some claims take longer. If the MAC needs more information from the provider — such as medical records to justify the charge — the clock restarts when the provider sends those records. A claim that requires medical review can take 60 days or more.

Claims that are denied or partially denied also take longer to process because the MAC must document the reason. If a service is not covered under Original Medicare, or if the provider charged more than the Medicare-approved amount, the MAC will explain this on the EOB and tell you and the provider what to do next.

Seasonal delays happen in January and after major holidays when claim volume is highest. If you submitted a claim in late December, expect it to take longer than 30 days. If you have not received an EOB within 45 days of your service date, you can contact the MAC to ask about the status.

Part A claims versus Part B claims — different processors

Part A claims cover hospital stays, skilled nursing facility care, home health services, and hospice. Part B claims cover doctor visits, lab work, imaging, durable medical equipment, and outpatient therapy. In most states, these go to different MACs. For example, in California, one MAC handles Part A and a different MAC handles Part B.

This matters if you have a question about a claim. If you are asking about a hospital bill, you need the Part A MAC. If you are asking about a doctor's office visit, you need the Part B MAC. Calling the wrong one will not get you an answer — they will tell you to call the other contractor.

Your EOB will show which MAC processed the claim. If you are unsure, call 1-800-MEDICARE and describe the service (hospital, doctor visit, lab work, etc.). They will tell you which MAC to contact and provide the phone number.

How to check on a claim or file an appeal

You can check the status of a claim by calling your regional MAC directly. Have your Medicare number and the date of service ready. The MAC can tell you whether the claim has been received, whether it is being reviewed, or whether payment has been sent.

If you disagree with how the MAC processed your claim — for example, if they denied a service you think should be covered — you have the right to appeal. The appeal process starts with the MAC that made the decision. You must file your appeal within 120 days of the date on your EOB. The MAC will review your appeal and send you a written decision.

If you lose the appeal at the MAC level and the amount in question is at least $200, you can request a hearing before an independent reviewer. This process takes longer but gives you another chance to present your case. The MAC's EOB will explain how to request an appeal and what documents to send.

What Original Medicare claims do not include

Original Medicare claims are only for services covered under Part A and Part B. If you have a Medigap policy or Medicare Advantage plan, those insurers handle their own claims separately. Your Medigap insurer will receive a copy of your Original Medicare EOB and will process their portion of the bill based on your policy.

Prescription drug claims (Part D) go to your Part D plan, not to a MAC. Dental, vision, and hearing services are not covered by Original Medicare, so there are no claims to process for those services. If you want coverage for those, you need to purchase a separate policy.

Frequently Asked Questions

How long does it take to get paid after the MAC receives my claim?

A clean claim — one with all required information — usually processes within 30 days of the date the MAC receives it. If the MAC needs more information from your provider, the timeline restarts when they send it. Claims that require medical review or are denied can take 60 days or longer.

Can I contact the MAC directly if I have a question about my bill?

Yes. You can call your regional MAC to ask about a claim status, request a copy of your claim, or file an appeal. You will need your Medicare number and the date of service. Call 1-800-MEDICARE first if you do not know which MAC to contact.

What if the MAC denies my claim?

The MAC will send you an EOB explaining why the claim was denied. You have 120 days from the date on the EOB to file an appeal. The MAC will review your appeal and send a written decision. If you disagree with that decision and the amount is at least $200, you can request an independent review.

Do I have to pay the provider while waiting for the MAC to process my claim?

No. Your provider should not bill you while the claim is being processed. If they do, ask them to wait for the MAC's decision. If a provider bills you before the claim is processed, contact the MAC to report it.

What is the difference between an EOB and a bill?

An EOB is a record of what the MAC did with your claim — it shows what was charged, what Medicare approved, and what you owe. A bill is a request for payment. You should receive an EOB from the MAC; the provider may also send you a bill showing your share of the cost after Medicare pays.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.