How Medicare claims work and who submits them
In most cases, you do not submit a Medicare claim yourself. Your doctor's office, hospital, or other healthcare provider submits the claim to Medicare on your behalf. They send it electronically or by mail within a set timeframe after you receive care. Medicare then reviews the claim, decides what portion it will pay, and sends you an Explanation of Benefits (EOB) — a document that shows what was billed, what Medicare paid, and what you owe.
However, there are situations where you may need to submit a claim yourself: if a provider refuses to submit one, if you paid out of pocket and want to request reimbursement, or if you received care from a provider who does not normally bill Medicare. Understanding when and how to submit a claim protects you from losing money on services Medicare should have covered.
Key Takeaways
- Most providers submit claims to Medicare automatically, but you can request a claim form if they refuse or if you paid upfront.
- You will need your Medicare card, an itemized receipt from the provider, and proof of payment to submit a claim yourself.
- The CMS-1500 form is the standard paper claim form for Medicare, available free from Medicare.gov or your provider.
- Paper claims typically take four to six weeks to process, while electronic claims are faster but require a provider account.
- Your Explanation of Benefits will show what Medicare paid and what you owe; keep it to track your out-of-pocket costs.
When you need to submit a claim yourself
Most of the time, your provider handles the paperwork. But if a provider says they do not bill Medicare, or if you paid the full bill upfront and want Medicare to reimburse you, you can submit a claim. You may also need to submit a claim if you received care while traveling outside the United States but within a country where Medicare covers emergency services.
Before you submit a claim yourself, ask your provider to submit it first. Many providers will do so if you ask, even if they initially said they do not. If they genuinely refuse, ask them for an itemized receipt showing the date of service, what was done, the cost, and their National Provider Identifier (NPI) — a 10-digit number that identifies them to Medicare. Without this information, Medicare cannot process your claim.
What documents you need to gather
To submit a Medicare claim, collect these documents before you start:
- Your Medicare card (the front and back)
- An itemized receipt or invoice from the provider showing the date of service, description of the service or supply, the charge, and the provider's NPI
- Proof that you paid (a receipt, cancelled check, or credit card statement)
- Any other medical records related to the service, if Medicare might question whether it was medically necessary
If you do not have an itemized receipt, contact the provider and ask for one. A receipt that just says "office visit — $150" is not enough; Medicare needs to know what was actually done. If the provider will not give you an itemized receipt, write down everything you remember about the visit — the date, the provider's name, what was treated or tested — and include that with your claim.
How to fill out and submit the CMS-1500 form
The standard Medicare claim form is called the CMS-1500. You can read it free from Medicare.gov, or ask your provider to give you a copy. The form has 33 numbered boxes. You do not need to fill every box — only the ones that explore to your situation.
Here are the boxes you will almost always need to complete:
| Box Number | What Goes Here |
|---|---|
| 1 | Check the box for Medicare |
| 1a | Your Medicare number (from your Medicare card) |
| 2 | Your full name |
| 3 | Your date of birth and sex |
| 5 | Your address |
| 24 | Date of service (when you received care) |
| 24d | The procedure code for what was done (ask your provider for this) |
| 24e | The charge for that service |
| 25 | Your diagnosis code (ask your provider) |
| 26 | The provider's NPI (10-digit number) |
| 31 | The provider's signature or stamp |
If you are unsure what code goes in a box, call your provider and ask. They can tell you the procedure code and diagnosis code in seconds. Print the form clearly in black ink, or type it if you have access to a computer. Medicare's system can read typed forms more easily than handwritten ones.
Where to send your claim and how long it takes
Once you have filled out the form, attach a copy of your itemized receipt and proof of payment. Do not send the originals — send copies only. Mail the package to your Medicare Administrative Contractor (MAC), which is the regional office that processes Medicare claims in your state.
To find your MAC's mailing address, go to Medicare.gov, search for "Medicare Administrative Contractor," and select your state. The page will show you the correct address for paper claims. Some MACs also accept claims by fax or through an online portal; check your MAC's website to see what options are available.
Paper claims typically take four to six weeks to process. You will receive an Explanation of Benefits in the mail showing what Medicare decided to pay. If Medicare denies the claim or pays less than you expected, the EOB will explain why and tell you how to appeal.
What happens after you submit: understanding your Explanation of Benefits
After Medicare processes your claim, you will receive an Explanation of Benefits (EOB) in the mail. This is not a bill — it is a record of what happened with your claim. The EOB shows the date of service, what was billed, what Medicare's allowed amount is, what Medicare paid, and what you owe.
Medicare's allowed amount is often less than what the provider charged. For example, a provider might charge $200 for a service, but Medicare's allowed amount might be $120. If the provider is in-network (accepts Medicare), they cannot charge you more than your copay or coinsurance on top of what Medicare pays. If the provider is out-of-network, you may owe the difference.
Keep your EOB. It is proof that you submitted the claim and what Medicare decided. If you have a supplemental insurance plan (Medigap) or a Medicare Advantage plan, you may be able to forward the EOB to them for additional coverage. You will also need the EOB if you want to appeal Medicare's decision.
What to do if Medicare denies your claim
If Medicare denies your claim, the EOB will say why. Common reasons include: the service was not medically necessary, the provider is not enrolled in Medicare, or the claim was submitted too late. Read the reason carefully — it tells you whether you can fix the problem and resubmit.
If you disagree with Medicare's decision, you have the right to appeal. You have 120 days from the date on your EOB to file an appeal. To appeal, write a letter to your MAC explaining why you think the claim should be paid, attach a copy of your EOB and any supporting medical records, and mail it to the address on your EOB. You do not need a lawyer, but you can hire one if you choose.
Frequently Asked Questions
Can I submit a claim online instead of by mail?
Most people cannot submit claims online themselves — that option is for healthcare providers and billing services. However, some Medicare Administrative Contractors accept claims by fax or through a find online portal. Check your MAC's website to see what methods they accept. If your provider has a patient portal, you may be able to request a claim submission through that.
What if I lost my receipt from the provider?
Contact the provider and ask for a duplicate itemized receipt. If they cannot provide one, write down everything you remember about the visit — the date, the provider's name, what service you received, and the amount you paid — and include that with your claim. Medicare may contact the provider to verify the information before paying.
How long do I have to submit a claim after I receive care?
You should submit a claim as soon as possible, but Medicare generally accepts claims up to one year after the date of service. However, waiting longer makes it harder to find receipts and remember details. Submit within a few months if you can.
Will I have to pay the provider while my claim is being processed?
That depends on your agreement with the provider. Some providers will wait for Medicare's decision before asking you to pay. Others may ask you to pay upfront and then reimburse you after Medicare pays. Ask the provider about their policy before you leave.
What if the provider says they do not accept Medicare?
Some providers do not enroll in Medicare, which means they do not bill Medicare and may charge you more than Medicare's allowed amount. Before receiving care from a non-Medicare provider, ask what they will charge and whether they will submit a claim to Medicare on your behalf. You can still submit a claim yourself, but Medicare will only pay its allowed amount, and you may owe the difference.