What You Need to Do to File a Medicare Claim

Most of the time, you do not file a claim yourself — your doctor or hospital sends it to Medicare automatically. But if you paid out of pocket for a service you think Medicare should cover, or if a provider did not submit the claim, you can file it yourself. You will need the itemized bill from the provider, your Medicare card, and the dates of service. The process differs slightly depending on whether you have Original Medicare (Parts A and B) or Medicare Advantage, and whether the service was inpatient or outpatient.

Original Medicare claims go to a regional contractor called a Medicare Administrative Contractor (MAC), not to Medicare directly. Each state has one or more MACs that handle claims for that region. Medicare Advantage claims go to your insurance plan, not to Medicare. Knowing which you have and which contractor handles your area is the first step.

Key Takeaways

  • Providers submit most claims automatically, so check your Explanation of Benefits first to see if Medicare already received and processed the claim.
  • Original Medicare claims go to your regional Medicare Administrative Contractor, which you can find by entering your ZIP code on the CMS website.
  • You will need the itemized bill, your Medicare card number, and the date of service; claims can be filed by mail, online, or through a provider.
  • Medicare typically processes claims within two to four weeks, and you will receive an Explanation of Benefits showing what was paid and what you owe.
  • If Medicare denies the claim, you have 120 days from the date on the denial notice to request a reconsideration.

Check Your Explanation of Benefits Before Filing

Before you file anything, look for an Explanation of Benefits (EOB) in your mail or online account. This is the notice Medicare sends after a claim is processed, showing what the provider charged, what Medicare paid, and what you owe. If you have Original Medicare, check your online account at Medicare.gov by logging in with your username and password. If you have Medicare Advantage, log into your plan's website instead.

If you find an EOB for the service in question, the claim was already filed and processed — you do not need to file again. If the claim was denied and you disagree with the reason, that is a different process (see the appeals section below). If you find no record of the claim at all, or if the EOB shows it was never submitted, then you should file it yourself.

Gather the Documents You Need

You will need three things to file a claim: the itemized bill from the provider, your Medicare card, and proof of the dates of service. The itemized bill should list each service or supply separately with the charge for each one — not just a total. If the provider gave you only a receipt or summary bill, call their billing department and ask for an itemized statement. This is important because Medicare needs to see exactly what was billed in order to process the claim.

Your Medicare card shows your Medicare number, which the contractor needs to match the claim to your account. Keep the card number handy. If you no longer have your card, you can find your number on any previous EOB, or by calling Medicare at 1-800-MEDICARE (1-800-633-4227). Write down the dates the service was provided — the bill should show these, but having them separate makes the filing process faster.

Find Your Regional Medicare Administrative Contractor

Original Medicare claims do not go to a central Medicare office. Instead, they go to a Medicare Administrative Contractor — a private company that processes claims for your region. Each state is divided into one or more MAC regions, and you must send your claim to the right one or it will be delayed.

To find your MAC, go to CMS.gov/mac and enter your ZIP code. The site will show you the name of your contractor, their mailing address, and whether they accept online filing. Some MACs allow you to file claims through a web portal; others accept only mail or fax. The CMS website will tell you which methods your MAC uses. If you have Medicare Advantage, skip this step — you file directly with your insurance plan instead.

File Your Claim by Mail, Online, or Through Your Provider

You have three ways to submit a claim to your MAC: by mail, online (if your MAC offers it), or by asking the provider to file it for you. The fastest method is usually online, if available — most MACs process online claims within two to four weeks. Mailed claims take longer because they must be scanned and entered into the system by hand.

To file by mail, use Form CMS-1500 (for doctors and outpatient services) or Form UB-04 (for hospitals and inpatient services). These forms are free and available on the CMS website. Fill in your Medicare number, the dates of service, the provider's information, and the itemized charges. Attach a copy of the itemized bill and mail everything to your MAC's address. Include a cover letter with your name, Medicare number, and phone number so the contractor can contact you if there are questions.

If your MAC has an online portal, you can upload the bill and your information directly — this is usually faster than mail. Ask your provider's billing department whether they will file the claim for you; many will do this at no charge, even if they did not submit it the first time. If the provider agrees, give them a copy of the itemized bill and your Medicare card number, and ask them to confirm when the claim has been sent.

What Happens After You File

After your MAC receives the claim, they will review it to see whether the service is covered under Medicare rules and whether the charge is reasonable. This review usually takes two to four weeks. You will then receive an Explanation of Benefits in the mail showing what Medicare decided to pay.

The EOB will show the provider's charge, the amount Medicare approved, the amount Medicare paid (usually 80 percent of the approved amount after you meet your deductible), and the amount you owe. If you have a Medigap or other supplemental insurance, send a copy of the EOB to that plan — they may pay some or all of your remaining balance. If you have Medicare Advantage, the process is different because your plan has already negotiated rates with providers, and your out-of-pocket costs are set by your plan.

What to Do If Medicare Denies Your Claim

If the EOB shows that Medicare denied the claim, it will include a reason — for example, "not medically necessary," "not covered," or "exceeded frequency limit." You have the right to ask Medicare to reconsider. You have 120 days from the date on the denial notice to request a reconsideration.

To request a reconsideration, write a letter to your MAC explaining why you think the claim should be paid. Include your Medicare number, the date of service, the provider's name, and a copy of the denial notice. Explain any new information that might change the decision — for example, if the service was medically necessary because of a condition that developed after the initial claim. Mail the letter to your MAC's address (shown on the denial notice). The MAC will review your request and send you a new decision, usually within 30 days.

Frequently Asked Questions

Do I have to file the claim myself, or will my doctor do it?

Your doctor should file it automatically as part of their billing process. If they did not, ask them to file it for you — most will do this at no charge. If they refuse, you can file it yourself using the steps above. Always check your Explanation of Benefits first to confirm the claim was not already submitted.

What if I lost the itemized bill from the provider?

Call the provider's billing department and ask for an itemized statement of charges for the date of service. They are required to provide this. If the provider is no longer in business, contact your MAC — they may be able to help you locate the records or process the claim without the original bill if you can provide other proof of the service.

How long does it take Medicare to pay a claim?

Most claims are processed within two to four weeks of receipt. Online submissions are usually faster than mailed claims. You can check the status of your claim by logging into your Medicare account at Medicare.gov or by calling your MAC directly — the phone number is on any EOB you have received.

Can I file a claim for a service from more than a year ago?

Medicare has a time limit for filing claims, usually one year from the date of service. If you are filing late, include a letter explaining the delay. Some MACs will accept late claims if you have a good reason, such as not receiving a bill from the provider. Contact your MAC before mailing to ask whether they will consider your claim.

What is the difference between filing a claim and appealing a denial?

Filing a claim is the first step — you send in the bill and ask Medicare to pay it. If Medicare denies the claim, appealing is the second step — you ask them to reconsider their decision. You have 120 days from the denial notice to appeal. If you disagree with the appeal decision, you can request a hearing before an administrative law judge, but this is a separate process with its own timeline.