CO 146: Invalid Diagnosis Code
The diagnosis was not valid on that date of service.
Check the diagnosis against the ICD-10 set in force on the date of service, then rebill.
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What CO 146 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 diagnosis was deleted or revised in the annual October update.
A code was used before its effective date.
How to Fix CO 146, Step by Step
Check the diagnosis against the ICD-10 set in force on the date of service, then rebill.
- 1Step 1: Read the remark code. Find the remark code printed next to CO 146 on the 835 or EOB. It says what the payer wants back. The usual ones are MA63.
- 2Step 2: Find the cause. Match the denial to one of the 2 causes in Why It Fires above, and fix that one.
- 3Step 3: Do this. Check the diagnosis against the ICD-10 set in force on the date of service, then rebill.
- 4Step 4: Attach the documentation. The diagnosis code valid on the date of service.
The common mistake. Do not appeal. The October changes catch out claims that span the boundary, and a correction is faster than an argument.
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 146 description
The diagnosis was not valid on that date of service.
The diagnosis was not valid on that date of service. 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.
The Remark Code Beside It
The adjustment code says the claim was reduced. The remark code printed next to it says why, and it is the one that tells you what to send back.
| Remark | What it means |
|---|---|
| MA63 | The principal diagnosis is missing, not coded to full specificity, or not valid on the date of service. |
Related Codes
Your Questions Answered
What does CO 146 mean?
The diagnosis was not valid on that date of service. Contractual obligation. The provider absorbs it and cannot bill the patient.
Can you appeal CO 146?
Fix and resubmit. Check the diagnosis against the ICD-10 set in force on the date of service, then rebill.
Why does CO 146 happen?
The diagnosis was deleted or revised in the annual October update. A code was used before its effective date.
What documentation wins a CO 146 appeal?
The diagnosis code valid on the date of service.
How do I fix a CO 146 denial?
Step 1: Read the remark code. Find the remark code printed next to CO 146 on the 835 or EOB. It says what the payer wants back. Step 2: Find the cause. Match the denial to one cause: The diagnosis was deleted or revised in the annual October update. A code was used before its effective date. Step 3: Do this. Check the diagnosis against the ICD-10 set in force on the date of service, then rebill. Step 4: Attach the documentation. The diagnosis code valid on the date of service.
Most searched: CO 97 · CO 96 · OA 23 · PR 204 · CO 109 · CO 197 · CO 45 · CO 50
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