CO-15 Denial Code: Authorization number is missing, wrong, or doesn't fit the claim

What CO-15 means

CO-15 means the claim's authorization number is the issue: it is blank, mistyped, expired, or does not cover the exact codes, dates, units, or rendering provider billed. It differs from CO-197, where no authorization was obtained at all. Usually a valid authorization exists - the fix is getting the correct number onto a corrected claim so it matches what was approved.

Common causes

• The authorization number was left off or mistyped on the claim.
• The auth on file doesn't match the billed CPT/HCPCS, units, dates, or rendering provider.
• The authorization expired before the date of service.
• The auth number was in an invalid format for the payer.

How to fix it

• Locate the correct, active authorization and confirm it covers the billed services, dates, units, and provider.
• Add or correct the authorization number and resubmit a corrected claim.
• If a valid auth was present, contact the payer with the auth details and request reprocessing.
• If services exceeded what was authorized, request an amended or additional authorization.

How to prevent it

• Capture and verify the authorization number and its scope before the service.
• Confirm the auth matches the planned codes, units, dates, and provider.
• Carry the auth number through to the claim automatically from your authorization-tracking workflow.

Appeal letter template

Fill in the bracketed fields, attach your supporting documentation, and send through the payer's appeal channel. This is a starting point — adjust to your payer's requirements.

Re: Authorization Number Correction/Appeal (CO-15) - Claim [Claim Number]

Patient: [Patient Name]   |   Member ID: [Member ID]
Date(s) of Service: [DOS]   |   Service(s): [CPT/HCPCS]

To Whom It May Concern:

Claim [Claim Number] was denied under CO-15 for a missing or invalid authorization number. Authorization [Auth Number], approved on [Auth Date], covers [CPT/HCPCS] for [DOS] under rendering provider [Provider/NPI]. The authorization details are enclosed.

We request that the claim be reprocessed with this authorization on file.

Sincerely,
[Your Name], [Practice Name]   |   [Phone]   |   [NPI/TIN]