CO-15CO group · Authorization

CO-15 denial code: the authorization number is missing or invalid

CO-15 is an authorization-data denial — and unlike a true medical-necessity fight, it often turns on a number that already exists or an auth that should have been granted after the fact.

CO-15 means the claim's authorization number is absent, invalid, or doesn't match the payer's record. It overlaps with CO-197 (auth absent) but points specifically at the auth number on the claim. The resolution is frequently administrative — supply or correct the number — and the appeal is for retroactive authorization, emergency exceptions, or a valid auth the payer failed to match.

What CO-15 means

When a service requires prior authorization, the approval number must be present and valid on the claim. A missing, mistyped, or mismatched number triggers CO-15. Sometimes the authorization exists and only the claim data is wrong; sometimes no auth was obtained at all.

Why CO-15 fires

  • The authorization number was omitted or entered incorrectly on the claim.
  • The number on the claim doesn't match the approved service, units, or dates.
  • No prior authorization was obtained for a service that required one.
  • The auth was issued to a different rendering provider or facility than the one billed.

Is CO-15 worth appealing?

Sometimes worth appealing

Correct it first when an auth exists: resubmit with the right number, provider, and dates. Appeal when no auth was obtained but one was clinically warranted — request retroactive authorization, cite the emergency or urgent-care exception where it applies, or show the payer failed to match a valid auth already on file.

How to resolve or appeal CO-15

  1. 1

    Confirm whether an auth exists

    If one was granted, the fix is usually a corrected claim with the right number and matching service details — not an appeal.

  2. 2

    Request retro-authorization

    Where no auth was obtained, many payers allow a retroactive request within a set window for urgent or emergent care. Submit the clinical justification.

  3. 3

    Invoke the emergency exception

    Emergency services generally cannot be denied for lack of prior authorization. If the service was emergent, appeal on that basis with the documentation.

CO-15 — frequently asked

CO-15 vs. CO-197?
They overlap. CO-197 says authorization was absent; CO-15 points specifically at a missing or invalid auth number on the claim. The remedies are similar — supply or correct the auth, or appeal for retro-authorization.
Can emergency care be denied for no authorization?
Generally no. Emergency services are typically protected from prior-authorization denials; appeal a CO-15 on emergent care with the records establishing the emergency.

Related guides

CO-197 · AuthorizationCO-16 · AdministrativeCO-50 · Medical necessity

Sources

Reason-code meanings are paraphrased from the X12 Claim Adjustment Reason Code list for plain-language reference; they are not reproduced verbatim. This is general information, not legal, coding, or medical advice — always confirm against the payer's remittance and policy.

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