CO 15: Invalid Authorization Number
The authorisation number is missing, invalid, or does not match.
Correct the auth number and resubmit. This is not an appeal.
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What CO 15 means
CO: Contractual obligation. The provider absorbs it and cannot bill the patient.
So the balance cannot move to the patient. Either the appeal recovers it or the practice absorbs it. That makes the appeal decision the whole decision on this line.
Is It Worth Appealing?
Fix and resubmit. This is a correction, not an appeal. Appealing burns the deadline.
Why It Fires
In the order we see it.
The authorisation number is missing, mistyped, or belongs to a different episode.
How to Fix CO 15, Step by Step
Correct the auth number and resubmit. This is not an appeal.
- 1Step 1: Read the remark code. Find the remark code printed next to CO 15 on the 835 or EOB. It says what the payer wants back.
- 2Step 2: Find the cause. Match the denial to one of the cause in Why It Fires above, and fix that one.
- 3Step 3: Do this. Correct the auth number and resubmit. This is not an appeal.
- 4Step 4: Attach the documentation. The correct authorisation number and its date range.
The common mistake. Do not appeal. Correct the number and resubmit.
Free: the Denial Code Appeal Playbook. 53 codes on one sheet: appeal, fix and resubmit, or let it go, and what to attach. Get the playbook
CO 15 description
The authorisation number is missing, invalid, or does not match.
The authorisation number is missing, invalid, or does not match. So the balance cannot move to the patient. Either the appeal recovers it or the practice absorbs it. That makes the appeal decision the whole decision on this line.
This is our plain-English wording, not the official X12 text. X12 asserts copyright over the published descriptions, so we write our own and say what it means for the money rather than restating the code.
Where this comes from. This is our own reading of the code, not the payer's and not a copy of the standards text. We classify it from how these denials actually resolve. Where we are unsure, we say so rather than guessing.
Your Questions Answered
What does CO 15 mean?
The authorisation number is missing, invalid, or does not match. Contractual obligation. The provider absorbs it and cannot bill the patient.
Can you appeal CO 15?
Fix and resubmit. Correct the auth number and resubmit. This is not an appeal.
Why does CO 15 happen?
The authorisation number is missing, mistyped, or belongs to a different episode.
What documentation wins a CO 15 appeal?
The correct authorisation number and its date range.
How do I fix a CO 15 denial?
Step 1: Read the remark code. Find the remark code printed next to CO 15 on the 835 or EOB. It says what the payer wants back. Step 2: Find the cause. Match the denial to one cause: The authorisation number is missing, mistyped, or belongs to a different episode. Step 3: Do this. Correct the auth number and resubmit. This is not an appeal. Step 4: Attach the documentation. The correct authorisation number and its date range.
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