CO-61 denial code
Adjusted for failure to obtain second surgical opinion
How to fix it
Confirm the requirement applied. Where it did, a retroactive opinion is rarely accepted; appeal on medical urgency where applicable.
How to prevent it
Identify plans with second-opinion requirements during verification for elective surgical scheduling.
In practice
A patient proceeds to an elective procedure their plan lists as requiring a second surgical opinion. None was obtained, and the claim returns CO-61.
Second opinion requirements are relatively rare now but survive in some plan designs for a defined list of elective procedures. Where they apply they are a condition of payment, not a recommendation.
Retroactive opinions are seldom accepted, since the requirement exists to inform the decision rather than to document it afterwards. The available arguments are that the procedure was urgent, that the requirement did not apply to this service, or that an opinion was obtained and not transmitted.
What sits behind it
These requirements attach to specific elective procedure lists rather than to surgery generally, and the lists are plan-specific. A requirement that applies to one carrier's members may be absent from another's entirely, which is why verification has to be per-plan rather than by general rule.
Urgency is the argument that succeeds most often. Where the clinical record shows the procedure could not reasonably wait for a second consultation, plans generally waive the requirement, but the documentation has to establish urgency contemporaneously rather than asserting it in the appeal.
Because the requirement is checked at scheduling or not at all, this belongs alongside authorisation in the pre-service workflow. Any plan carrying second-opinion conditions should be flagged so surgical scheduling triggers the check automatically rather than depending on someone remembering.
Related codes
Terms used here — Prior Authorization · Medical Necessity · Appeal
How we handle it — Prior Authorization · Denial Management · Eligibility Verification
Primary sources
The rules behind CO-61, 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.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-61
Rarely to any effect. The requirement exists to inform the decision, so an opinion produced afterwards does not satisfy the purpose and most plans reject it. The workable arguments are urgency, inapplicability to this procedure, or an opinion that was obtained but never transmitted.
It varies entirely by plan, and applies to defined lists of elective procedures rather than to surgery in general. Because one carrier's requirement may be absent from another's, this has to be verified per plan during surgical scheduling rather than assumed from experience.
Clinical urgency, supported by contemporaneous documentation showing the procedure could not reasonably wait. Plans generally waive the requirement in genuinely urgent cases, but the record has to establish that at the time, not in the appeal narrative written months later.
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