CO-15 denial code
The authorization number is missing, invalid, or does not apply
How to fix it
Retrieve the correct authorization number and confirm it covers this date of service, provider and procedure, then resubmit.
How to prevent it
Store authorization numbers against the specific service and date, and carry them onto the claim automatically.
In practice
A procedure requiring prior authorisation is performed and the authorisation number is entered on the claim. It returns CO-15 — the authorisation number is missing, invalid, or does not apply.
The number was real. It was obtained for the same patient and the same procedure, but for a date three weeks earlier that was rescheduled. The authorisation's valid date range had expired by the time the procedure took place.
This is the dominant form of CO-15: not a missing authorisation, but one that does not match what was actually performed — wrong date range, wrong procedure code, wrong site of service, or wrong rendering provider.
What sits behind it
Authorisation is granted against a specific set of facts, and any of them changing invalidates it. The approval covers named procedure codes, a named provider, a named facility and a defined date window. A claim that departs from any of those is unauthorised even though an authorisation exists.
The failure this exposes is storing authorisations against the patient rather than against the service. A record showing this patient has an authorisation cannot answer whether it covers this date, this code and this provider — which is the question adjudication actually asks.
Rescheduling deserves particular attention because it silently breaks authorisations that were correct when obtained. A confirmation step that re-checks the authorisation window whenever an appointment moves prevents most of this category.
Related codes
Terms used here — Prior Authorization · Denial · Eligibility Verification
How we handle it — Prior Authorization · Denial Management · Eligibility Verification
Primary sources
The rules behind CO-15, at the bodies that publish them.
- CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) (opens in a new tab)
Centers for Medicare & Medicaid Services — The rule imposing prior authorization decision timelines and API requirements on impacted payers. It is the single largest scheduled change to authorization workflow this decade.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
Every denial code with a guide
Authorization
Bundling
Contractual
Coverage
Data quality
Documentation
Eligibility
Liability and workers comp
Patient responsibility
Provider eligibility
Timely filing
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-15
Because the authorisation does not match what was billed. Approvals are granted against specific procedure codes, a specific provider and facility, and a defined date window. A rescheduled appointment falling outside the original window is unauthorised even though an authorisation exists.
Yes where a valid authorisation covering the actual service exists and was simply not carried onto the claim. Submit the authorisation number, approved codes and date range as evidence. Where no authorisation covering the service was obtained, most payers will not grant one retroactively.
Store authorisations against the specific codes, provider, facility and date range approved rather than against the patient, and re-verify the window whenever an appointment is rescheduled. Rescheduling silently invalidates authorisations that were correct when obtained.
Generally not. The CO prefix makes it a contractual obligation, and failure to obtain or convey authorisation is an administrative failure rather than a patient one.
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