CO-48 denial code
These procedures are not covered
How to fix it
Check whether an alternative covered code accurately describes the service. Otherwise obtain an advance beneficiary notice where applicable and bill the patient.
How to prevent it
Check benefit-level coverage during verification, not just active status.
In practice
A patient requests a cosmetic procedure that their plan does not cover. The practice bills it anyway and receives CO-48, with the full charge unpaid and no patient liability assigned.
Benefit exclusions are decided at plan design, not at adjudication. There is no medical necessity argument available because coverage was never in question — the plan simply does not buy this category of service for anyone.
Whether the patient can be billed depends entirely on what happened before the service. With a signed advance notice acknowledging non-coverage, they can. Without one, the practice is frequently barred by contract from collecting, and the charge becomes a write-off.
What sits behind it
The distinction from a medical necessity denial is the one that determines strategy. CO-50 means the service could be covered but this patient's circumstances did not justify it, which is appealable with clinical documentation. CO-48 means the service is outside the benefit entirely, which is not appealable on clinical grounds at all.
Occasionally a code is excluded while an accurate alternative describing the same work is covered, and checking for that is worth the few minutes it takes. This is legitimate only where the alternative genuinely describes what was performed; selecting a covered code for an excluded service is fraud, not optimisation.
The recurring version of this denial is a workflow problem rather than a billing one. Practices that identify commonly excluded services at scheduling, verify them specifically rather than checking general coverage, and collect an advance acknowledgement, stop absorbing the cost of a decision the patient made.
Related codes
Terms used here — Medical Necessity · Patient Responsibility · Eligibility Verification
How we handle it — Eligibility Verification · Patient Collections · Denial Management
Primary sources
The rules behind CO-48, at the bodies that publish them.
- 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 Benefit Policy Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — What Medicare covers and under what conditions, as distinct from how a claim is processed. The starting point for any coverage or medical necessity question.
- Advance Beneficiary Notice of Noncoverage (ABN) (opens in a new tab)
Centers for Medicare & Medicaid Services — The form and the rules for issuing it. Whether a non-covered service can be billed to the patient usually turns on whether a valid ABN was obtained beforehand.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-48
Not on clinical grounds, because necessity was never the issue — the plan does not cover the category for anyone. The only viable arguments are that the service was misclassified as excluded when it is not, or that an exception process exists under the plan documents.
When they were told before the service that it was not covered and agreed in writing to pay. That acknowledgement has to precede delivery; obtaining it afterwards does not satisfy most contracts and does not satisfy patients either.
CO-50 is a medical necessity determination — the service is covered in principle but the payer concluded it was not warranted here, which clinical documentation can challenge. CO-48 is a benefit exclusion, meaning the service sits outside the plan entirely and no documentation changes that.
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