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CO-15Denial code

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CO-15 Denial Code — Authorization Number Invalid or Missing — What It Means and How to Fix It

CO-15 fires when the authorization number on a claim is missing, wrong, or doesn't match the billed service — a fixable administrative error, not a coverage dispute.

75
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CO-15 Denial Code Description — What It Means in Medical Billing

The official CO-15 denial code description from the CARC system:

"The authorization number is missing, invalid, or does not apply to the billed services or provider."

CO-15 means the insurer received a claim with an authorization number that either wasn't provided, doesn't match their records, or was issued for a different service, provider, or date range than what was billed. It is one of the most correctable denial codes because the authorization almost always exists — the issue is a data matching problem, not a coverage problem.

CO-15 differs from CO-197 in an important way: CO-197 fires when no prior authorization was obtained at all. CO-15 fires when an authorization number was submitted but something about it is wrong or mismatched. The fix for CO-15 is correcting the authorization reference, not obtaining a new authorization.

CO-15 Denial Reason — Why This Denial Happens and How to Overturn It

CO-15 denials trace back to one of four common root causes.

1

The authorization number was entered incorrectly

Transposed digits, missing characters, or a format error in how the authorization number was entered on the claim. The fix is verifying the exact authorization number from the insurer's confirmation letter and resubmitting the corrected claim.

2

The authorization applies to a different provider

Authorizations are often issued to a specific provider NPI. If the claim was submitted under a different provider or group NPI than the one named in the authorization, CO-15 fires. Confirm the NPI on the authorization and the NPI on the claim match exactly.

3

The service doesn't match the authorization

The authorization was issued for a specific procedure code or service type, and the claim was billed for a different — or more specific — code. Review the procedure codes covered by the authorization against the codes billed and request an updated authorization if needed.

4

The service date is outside the authorization window

Authorizations have validity periods. If the service was rendered after the authorization expired or before it became effective, CO-15 fires. Confirm the authorization's effective and expiration dates against the service date on the claim.

CO-15 Denial Code Solution — Step-by-Step Resolution

1

Obtain the authorization confirmation letter

Contact your provider's billing office and request the exact authorization confirmation — the authorization number, the procedure codes covered, the date range, and the provider NPI it was issued under.

2

Compare against the claim

Identify the specific mismatch: wrong number, wrong provider, wrong procedure, or expired window. The remittance advice remark codes (N-codes) alongside CO-15 often identify the specific issue.

3

Correct and resubmit or appeal

If the authorization number was entered wrong, submit a corrected claim. If the authorization genuinely doesn't match because of a payer system error, file a formal appeal with the authorization confirmation letter attached documenting the authorization was valid for the billed service.

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Other codes and appeal guides

Denial codes on the EOB

CO-45 Charge exceeds fee schedule CO-50 Not medically necessary CO-16 Missing information CO-197 Prior authorization missing CO-97 Bundled into another payment CO-109 Claim sent to the wrong payer PR-96 Non-covered charge

How to appeal

How to appeal a health insurance denial Internal appeal vs. external review How to appeal a prior authorization denial How to appeal a Medicare denial Medicare Advantage vs. Original Medicare Mental health parity rights Mental Health Parity Act in plain English How to dispute a medical bill

Claim types

Medicare appeal Prior authorization appeal Medical bill dispute Mental health appeal Health insurance appeal

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