CO-233 denial code
Services related to a hospital-acquired condition or preventable medical error
How to fix it
Confirm the attribution. These are generally not payable and not billable to the patient.
How to prevent it
Present-on-admission documentation determines this; ensure it is captured accurately.
The CO prefix marks this a contractual obligation. The balance is absorbed by the provider under the payer agreement and cannot be transferred to the patient.
In practice
A patient develops a pressure ulcer during an admission. The condition was not present on admission, and services related to treating it return CO-233.
Payment policy excludes conditions the payer attributes to care rather than to the patient's underlying illness, and treats a defined list of serious events as never payable.
The determination rests almost entirely on present-on-admission indicators. Where the condition genuinely existed at admission and the indicator was coded wrongly, correcting it resolves the claim; where it did not, the exclusion applies.
What sits behind it
Present-on-admission coding carries more financial weight than its brevity suggests. A single indicator determines whether an entire cluster of services is payable, and it is frequently assigned by default rather than from the record.
The conditions in scope include pressure ulcers of specified stages, catheter-associated infections, certain surgical site infections, falls with injury and a list of serious reportable events. Each has published criteria rather than being assessed case by case.
These amounts are generally not billable to the patient either, which distinguishes them from ordinary non-covered services. The policy intent is that the cost sits with the provider, and billing the patient contradicts that directly.
Related codes
Terms used here — ICD-10-CM · Medical Necessity · Denial
How we handle it — Medical Coding · Denial Management · Practice Analytics
Primary sources
The rules behind CO-233, 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-233
The present-on-admission indicator assigned during coding. A single indicator can determine whether an entire cluster of services is payable, which is why assigning it from the record rather than by default matters more than its brevity suggests.
No. The policy intent is that the cost sits with the provider rather than moving to the patient, so billing them contradicts the rule directly. This distinguishes these adjustments from ordinary non-covered services.
Pressure ulcers of specified stages, catheter-associated infections, certain surgical site infections, falls with injury and a list of serious reportable events. Each carries published criteria rather than being assessed case by case.
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