What happens when you submit a Medicare claim
When you receive medical care — a doctor visit, hospital stay, lab test, or prescription — your provider usually sends the bill to Medicare automatically. You do not have to do anything in most cases. Medicare processes the claim, decides what portion it will pay based on your coverage type, and sends you an Explanation of Benefits (EOB) in the mail. This document shows what Medicare paid, what you owe, and why.
Sometimes you will need to submit a claim yourself. This happens when a provider does not bill Medicare directly, when you paid out of pocket and want reimbursement, or when a claim was denied and you are asking Medicare to reconsider. The process depends on whether you have Original Medicare (Parts A and B) or a Medicare Advantage plan, and what type of service you received.
Key Takeaways
- Most providers bill Medicare directly, so you receive an Explanation of Benefits in the mail rather than submitting anything yourself.
- If you must submit a claim, you will need the itemized bill from your provider, your Medicare card, and the correct form for the type of service.
- Original Medicare claims go to your regional Medicare Administrative Contractor; Medicare Advantage claims go to your plan.
- Paper claims take four to six weeks to process; you can check status online through your Medicare account or by calling the number on your card.
- If Medicare denies a claim, you have the right to ask them to review the decision, and the process and timeline differ depending on your plan type.
When you need to submit a claim yourself
Your provider is required to bill Medicare directly for most services covered under Original Medicare. However, some situations require you to file. If you paid a provider in full at the time of service and want Medicare to reimburse you, you will need to submit a claim with proof of payment. If a provider refuses to bill Medicare or says they do not accept Medicare, you can submit the bill yourself.
Out-of-network providers — those who do not have a contract with Medicare — sometimes do not bill automatically. Some seniors also receive care while traveling outside the United States and must submit claims after returning home. If a claim was rejected the first time, you may resubmit it with additional information or documentation to support your case.
How to submit a claim for Original Medicare (Parts A and B)
Original Medicare claims are submitted to your regional Medicare Administrative Contractor (MAC), not to a central Medicare office. Your MAC is the private company that processes Medicare claims in your state. To find your MAC, visit the Centers for Medicare & Medicaid Services website and enter your state, or call 1-800-MEDICARE.
You will need the CMS-1500 form for most outpatient services (doctor visits, lab work, imaging) or the UB-04 form for hospital or facility services. Both forms are available free on the CMS website. Fill in your information, your provider's information, the dates of service, the diagnosis codes, and the procedure codes. Attach the itemized bill from your provider — not a receipt, but an actual bill showing what was done and what was charged.
Mail the form and bill to your MAC. The address is on the CMS website for your state. Keep a copy for your records. Processing takes four to six weeks. You will receive an EOB in the mail showing what Medicare paid and what you owe.
How to submit a claim for Medicare Advantage
If you have a Medicare Advantage plan, you submit claims to your plan, not to Medicare directly. Your plan's contact information is on your member card and in your plan documents. Some plans have online portals where you can upload claims; others require you to mail them.
Call your plan first and ask what they need. Some plans accept the CMS-1500 form; others have their own claim form. Ask whether they want the original itemized bill or a copy, and confirm the mailing address. Medicare Advantage plans have their own timelines for processing — usually 30 days — so check your plan documents or call to ask.
If your plan denies a claim, the denial letter will explain why and tell you how to request a review. The review process for Advantage plans is different from Original Medicare, so follow the instructions in the denial letter carefully.
Submitting claims online
If you have Original Medicare, you can create a free account on Medicare.gov and submit claims through your online account. Log in, go to "Claims," and follow the prompts to upload your documents. You will still need the itemized bill and the correct form, but you avoid mailing.
Some providers also use PECOS (Provider Enrollment, Chain, and Ownership System) to submit claims on your behalf if you ask them to. Call your provider and ask whether they can file the claim for you electronically. This is faster than mailing and gives you a tracking number.
Medicare Advantage plans vary in whether they offer online submission. Check your plan's website or call the number on your card to ask.
What to do if your claim is denied
If Medicare denies your claim, you will receive a notice explaining the reason. Common reasons include: the service is not covered under your plan, the provider is not in-network (for Advantage plans), the service was not medically necessary, or the claim was submitted after the time limit.
You have the right to ask Medicare or your plan to reconsider. For Original Medicare, this is called a redetermination. You must request it within 120 days of the denial notice. Write a letter explaining why you believe the claim should be paid, attach any new information or documentation, and mail it to the address on the denial notice.
For Medicare Advantage, the process is called an appeal, and the timeline is shorter — usually 30 days. Your denial letter will explain the steps. If your plan denies the appeal, you can request an external review by an independent reviewer outside your plan.
Tracking your claim status
If you have Original Medicare, log into your Medicare.gov account to check the status of claims you submitted online. You can also call 1-800-MEDICARE and give them your claim number or the date of service.
If you submitted a paper claim by mail, keep the receipt or tracking number. When you call Medicare, have your Medicare number, the provider's name, the date of service, and the amount of the bill ready.
For Medicare Advantage, call your plan's member services number on your card. They can tell you whether your claim was received, is being processed, or has been paid.
Documents you will need
| Type of Claim | Documents Needed |
|---|---|
| Original Medicare outpatient (doctor, lab, imaging) | CMS-1500 form, itemized bill from provider, Medicare card |
| Original Medicare inpatient (hospital, facility) | UB-04 form, itemized bill from facility, Medicare card |
| Medicare Advantage | Plan's claim form (or CMS-1500), itemized bill, member card |
| Reimbursement for out-of-pocket payment | Itemized bill, proof of payment (receipt or bank statement), appropriate form |
Frequently Asked Questions
Do I have to submit a claim if my doctor already billed Medicare?
No. If your provider billed Medicare directly, Medicare will process it and send you an Explanation of Benefits. You do not need to do anything. If you are unsure whether they billed, call your provider's billing office and ask.
How long does it take Medicare to pay a claim?
Paper claims take four to six weeks. Online claims submitted through Medicare.gov may process faster. Medicare Advantage plans have their own timelines, usually 30 days. If a claim takes longer, call and ask for a status update.
What if I lost my itemized bill from the provider?
Call your provider's billing office and ask them to send you an itemized bill or a copy of what they submitted to Medicare. You need this to prove what service was provided and what it cost. A receipt showing only the amount you paid is not enough.
Can I submit a claim after one year?
Original Medicare has a time limit of one calendar year from the date of service. Medicare Advantage plans may have different limits. Check your plan documents or call to ask. If you are past the important date, call anyway — some exceptions exist, and it is worth asking.
What does "not medically necessary" mean on a denial letter?
It means Medicare reviewed the claim and decided the service was not appropriate for your condition, or that a less expensive option should have been used instead. You can request a redetermination and provide medical records or a letter from your doctor explaining why the service was necessary.