Quick Explanation
Denial code CO 46 indicates that the claim was submitted without a required prior authorization number, or the authorization number provided was invalid, expired, or incorrect. Payers use this code to halt payment when a procedure requires pre-service clinical or administrative approval that was not properly documented on the claim form.
Common Causes for CO 46
Denials with code CO 46 typically happen for the following specific reasons:
- The approved prior authorization number was completely omitted from Box 23 of the CMS-1500 claim form or Loop 2300 of the 837P electronic file.
- A typographical error or transposition of characters occurred when manually entering the authorization number into the billing system.
- The rendered services, CPT/HCPCS codes, or date of service did not match the specific parameters approved in the original authorization letter.
- The prior authorization had expired prior to the date of service, or the maximum number of approved visits or units had already been exhausted.
How to Prevent CO 46 Denials
To avoid receiving this denial in the future, implement these specific checks:
- Establish a mandatory pre-service verification workflow to identify which procedures and payer plans require prior authorization prior to scheduling.
- Utilize automated claim scrubbing software to flag claims for services requiring authorization that do not have Box 23 populated.
- Implement a dual-verification process to cross-reference the approved authorization letter details (CPT codes, date ranges, and rendering NPI) with the finalized billing codes.
- Track authorization utilization and expiration dates within the practice management system to secure timely extensions or new authorizations when care plans change.
Appeal Letter Template for CO 46
If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.
[Your Practice Header]
[Date]
[Payer Name]
[Appeals Department Address]
RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: CO 46 - Missing/invalid authorization number
Dear Appeals Department,
I am writing to appeal the denial of the above-referenced claim, which was denied with code CO 46: "Missing/invalid authorization number".
We are writing to appeal the denial of this claim under code CO 46 for a missing or invalid authorization number. Prior authorization was successfully obtained for this patient and these specific services prior to the date of service. Enclosed with this appeal is a copy of the active authorization letter issued by your organization, showing approval under authorization number [Insert Auth Number] for CPT code [Insert Code] with an active date range of [Insert Start Date] to [Insert End Date]. In accordance with standard CMS and industry billing guidelines, since the clinical necessity was reviewed and approved prior to the encounter, we respectfully request that you apply this authorization to the claim and reprocess it for immediate payment.
Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].
We respectfully request that you reprocess this claim for payment.
Sincerely,
[Your Name]
[Title]
[Practice Name]
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