What happens when you file a Medicare claim
When you file a Medicare claim, you are sending a record of a medical service or supply you received to Medicare so they can decide whether to pay for it. Most of the time, your doctor's office or hospital files the claim for you automatically — you do not have to do anything. But if a provider does not file, or if you paid out of pocket and want to be reimbursed, you will need to file the claim yourself.
The claim includes details like the date of service, what was done, the cost, and your Medicare number. Medicare reviews it against your coverage rules and sends a decision to you and the provider. The whole process usually takes two to four weeks, though it can be faster or slower depending on whether Medicare needs more information.
Key Takeaways
- Most providers file Medicare claims automatically, so check your Explanation of Benefits (EOB) before filing yourself to avoid duplicate claims.
- You can file a claim yourself using Form CMS-1500 (for providers) or Form CMS-1490S (for patients), available free from Medicare.gov or by phone.
- You will need your Medicare number, the provider's information, the date of service, and an itemized receipt or invoice showing what was billed.
- Mail paper claims to your regional Medicare Administrative Contractor (MAC), which you can find by entering your ZIP code at the MAC locator on Medicare.gov.
- Keep copies of everything you send and watch for your Explanation of Benefits in the mail to see whether Medicare approved the claim.
When you need to file a claim yourself
Your provider is required to file a claim if they accept Medicare. But sometimes they do not, or they file late. You should file a claim yourself if: you paid the provider in full and they have not filed within 30 days; the provider says they do not take Medicare; you received care out of state or at an urgent care center that did not file; or you want to appeal a claim that was denied or underpaid.
Before you file, check your mail for an Explanation of Benefits (EOB). This is a notice from Medicare that shows what they received and what they paid. If an EOB already exists for that service, filing again creates a duplicate claim, which can slow down payment. If you do not see an EOB within 30 days of paying, then filing yourself is the right move.
Documents and information you need to gather
Collect these items before you start: your Medicare card (or your Medicare number); the name, address, and phone number of the provider who gave you the service; the date you received the service; an itemized receipt or invoice showing exactly what was billed and how much; and your signature.
The itemized receipt is the most important piece. It must show the specific service or supply (not just "office visit" but "office visit, established patient, 99213"), the date, the provider's name and license number if available, and the charge. If the provider gave you only a receipt with a total, ask them for an itemized version before you file. Medicare cannot process a claim without knowing what they are paying for.
How to file a paper claim by mail
Paper claims go on one of two forms. If you are a patient filing for yourself, use Form CMS-1490S (Patient Request for Medical Payment). If a provider is filing on your behalf (because you are helping them submit it), they use Form CMS-1500. Both are free and available at Medicare.gov or by calling 1-800-MEDICARE.
Fill out the form completely, attach a copy of your itemized receipt, and mail it to your regional Medicare Administrative Contractor (MAC). Your MAC is the company that processes Medicare claims in your state. Find your MAC by going to Medicare.gov, clicking "Contacts," then "Medicare Administrative Contractors," and entering your ZIP code. The site will show you the mailing address for paper claims in your region.
Keep a copy of everything you mail — the form, the receipt, and a list of what you included. Mail it certified mail with return receipt if the claim is large or if the provider is disputing whether they filed. Standard mail is fine for routine claims.
Filing a claim online or by phone
Not all Medicare Administrative Contractors accept online claim filing from patients, but some do. Check your MAC's website (found the same way as the mailing address) to see if they have an online portal. If they do, you can upload your form and receipt directly instead of mailing.
You can also call your MAC directly to ask whether they will accept a claim over the phone. Some will take the information verbally and file it for you. The MAC phone number is on the Medicare.gov MAC locator page. Have your Medicare number, the provider's information, and the date of service ready when you call.
What happens after you file
Medicare sends your claim to the appropriate MAC, which reviews it against your coverage rules. They check whether the service is covered under your plan, whether the provider is in-network (if you have a plan that uses networks), and whether the charge is reasonable. This review usually takes two to four weeks.
You will receive an Explanation of Benefits (EOB) in the mail showing Medicare's decision. The EOB tells you whether they approved the claim, how much they are paying, how much you owe, and whether you can appeal if you disagree. Keep this notice — you will need it if you want to challenge the decision or if the provider asks you about payment status.
If Medicare approves the claim, they send payment to the provider if the provider is in-network, or to you if you paid out of pocket. If the provider is out-of-network, Medicare may send payment to you even if the provider filed the claim. In that case, you are responsible for paying the provider.
Common mistakes to avoid
Do not file a claim if an EOB already exists for that service — check your mail first. Do not submit a claim without an itemized receipt; Medicare will deny it and ask you to resubmit. Do not mail your original Medicare card or insurance documents; send copies only. Do not assume the provider filed just because you saw them; ask them directly or check for an EOB after 30 days.
Do not file multiple copies of the same claim to speed things up. Duplicate claims create confusion and can delay payment. If you have not heard back after four weeks, call your MAC instead of filing again. Do not ignore an EOB that shows a denial or underpayment; you have a right to appeal, and the EOB will explain how.
Frequently Asked Questions
How long does it take Medicare to pay a claim?
Most claims are processed within two to four weeks of receipt. Complex claims or claims that need more information can take longer. If you have not received an EOB after four weeks, call your Medicare Administrative Contractor to check the status.
What if Medicare denies my claim?
The EOB will explain why. Common reasons are that the service is not covered, the provider is not in-network, or the charge exceeds what Medicare considers reasonable. You can appeal by following the instructions on the EOB. You usually have 120 days from the date of the EOB to file an appeal.
Do I have to file a claim if I have a Medigap or Medicare Advantage plan?
No. Your primary provider files with Medicare, and Medicare automatically forwards the claim to your supplemental plan. You do not file separately. If a provider refuses to file with Medicare, contact your supplemental plan's customer service for help.
Can I file a claim for a service I received years ago?
Medicare has a time limit for filing claims, usually one calendar year from the date of service. If you are past that important date, contact your MAC to ask whether they will make an exception. Bring documentation of why the claim was not filed sooner.
What if the provider and Medicare disagree on the charge?
Medicare pays based on their fee schedule, not the provider's bill. If the provider charged more than Medicare pays, you may owe the difference if the provider is out-of-network. If the provider is in-network, they agreed to accept Medicare's payment as full payment and cannot bill you for the rest.