What does denial code CO-15 mean?

CO-15 means: The authorization number is missing, invalid, or does not apply to the billed services or provider.. UnitedHealthcare determined that the claim should have been processed based on a referral or authorization that was not in place at the time of service. For certain services or plan types, UHC requires a referral from the member's primary care provider or an approved authorization before the service can be covered. Without this documentation, the claim is denied, and you cannot bill the member.

How do I resolve a CO-15 denial?

Verify whether the service requires a referral under the member's plan design. Check UHCprovider.com > Coverage and payments > Prior authorization to determine if referral is required. Review the member's plan type (open access, gated, tiered) to understand referral requirements. Some plan types (Gated, HMO) require referrals; others do not. Obtain a referral from the member's primary care provider if not already in place. Submit the referral request through UHCprovider.com > Sign In > Prior Authorizations or through the primary care provider's office. For individual exchange plans, referral requirements may vary; verify specific plan rules. See full Medicare contractor resolution steps at tryarceum.com.

Can I appeal a CO-15 denial?

CARC 15 has a 35% recovery rate and typically resolves in 21-45 days. Resolution difficulty is rated Hard.

CARC Code

15

🔴 Hard Denial

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

authorization

Resolution: 35%Hard difficulty21-45 days avg

How to resolve this denial

Which payer denied this claim?

▶✓ Pre-action checklist — verify before contacting the payer

Was prior authorization required for this service? Check the payer's auth requirement list.
If auth was obtained, verify it covers the specific procedure, date, and provider.
Some payers allow retroactive auth within a short window — check the payer's policy.

Still denied?

Formal Appeal

If the payer upheld the denial after reconsideration, you can submit a formal appeal.

What you'll need

*
Copy of member's plan document showing referral requirements
*
EOB or denial letter citing missing referral
*
Referral from primary care provider (if obtained after service)
*
Clinical documentation demonstrating medical necessity
*
Explanation of why referral was not obtained before service
*
Evidence that service was urgent or emergent (if applicable)
*
Clinical guidelines supporting the need for immediate specialist care
*
A written appeal letter explaining why the denial should be overturned

Deadline: 12 months total from original EOB date for both reconsideration and appeal combined from the reconsideration decision.

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▶More about CO-15 — stats, related codes, appeal template

35%

Recovery Rate

21-45 days

Avg. Resolution

Hard

Difficulty

Common

Frequency

Payer-Specific Notes

How major payers handle CARC 15 by specialty.

Blue Cross Blue Shield

BCBS requires appeal submission within 180 days for most plans.

Common 835 Combinations

CARC 15 most often appears with these Group Code + RARC combinations on 835 remittances.

COCO-15This combination indicates a contractual denial due to an authorization issueAppealable

Look up any combination →

Appeal Letter Template

Generic appeal template for CARC 15 denials.

We are submitting a formal appeal for claim [CLAIM_NUMBER] for patient [PATIENT_NAME], date of service [DOS]. This claim was denied/adjusted with CARC 15 indicating: "The authorization number is missing, invalid, or does not apply to the billed se." We have reviewed the claim and are providing the attached documentation to support reconsideration. [SUPPORTING_DOCUMENTATION]. Please reconsider payment per the terms of our contract.

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