Medicare Denied Claim as a Duplicate Submission
Does your notice say something like this?
"This claim has already been processed"
"This service has already been paid"
"A duplicate claim or service was submitted"
If so, you're in the right place. Here's what it means and what to do.
What This Means
Medicare denied this claim because it appears to be a duplicate — meaning the same service, for the same patient, on the same date, was already submitted and processed. In most cases, the original claim was already handled correctly and this second submission was sent by mistake.
This is a billing office issue. You do not need to do anything unless you are being incorrectly billed.
Why This Happens
- The billing office submitted the claim more than once. This is the most common cause. It can happen when staff resubmit a claim thinking the first one didn’t go through.
- An automatic resubmission system sent it again. Some billing systems automatically resend claims that haven’t been paid within a set time, which can create duplicates.
- The provider tried to correct a claim but didn’t mark it properly. When fixing an error on a previously submitted claim, the billing office needs to indicate it’s a corrected claim, not a new one. If they don’t, Medicare treats it as a duplicate.
- The same service was performed more than once on the same day. If you genuinely had the same type of service twice in one day, the claim needs a special modifier to tell Medicare these were separate services. Without it, Medicare sees a duplicate.
Should You Appeal?
In most cases, a formal appeal is not needed or helpful. If the original claim was already paid, the duplicate denial is correct and there’s nothing to appeal.
If the original claim was not paid, or if you genuinely received two separate services that Medicare is treating as duplicates, the provider’s billing office can usually fix this by resubmitting with the correct information or modifiers.
A formal appeal may be needed in rare cases where the provider and Medicare disagree about whether the services were truly separate.
What To Do Next
- Check your Medicare Summary Notice (MSN). Look for the original claim to see if it was already paid. If it was, this duplicate denial is correct and no action is needed.
- Contact your provider’s billing office if the original claim was not paid. Let them know the claim was denied as a duplicate (code CO-18) and ask them to investigate.
- Do not pay a bill related to this denial. A duplicate denial does not create a new charge. If you receive a bill, call the billing office and explain the situation.
- If you had the same service twice on the same day, tell the billing office. They may need to add a modifier to distinguish the two services and resubmit.
- If you need help, call 1-800-MEDICARE (1-800-633-4227) or contact your State Health Insurance Assistance Program (SHIP) for free assistance.
Sources
- X12: Claim Adjustment Reason Codes — official CARC code definitions
- Medicare.gov: Your Medicare Rights & Appeals
- Medicare.gov: Medicare Summary Notice
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Not sure which you have? Check the top of your denial notice. If it names a private insurance company (like Humana, UnitedHealthcare, or Aetna), you have Medicare Advantage. If it says "Centers for Medicare & Medicaid Services," you have Original Medicare.
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This information is for educational purposes only and is not legal or medical advice. Always verify with your doctor's office and insurance company.