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CO-233 Denial Code: Hospital-Acquired Condition

CO-233 means the services or charges relate to treatment of a hospital-acquired condition or a preventable medical error, so the payer will not pay for them. Under the CO group, the provider absorbs the cost and generally cannot bill the patient.

Quick facts

Code
CO-233 (CARC 233)
Status
Active In use since January 24, 2010.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider or facility bears the cost of the condition or error. It generally cannot be billed to the patient.
Official description
Services/charges related to the treatment of a hospital-acquired condition or preventable medical error.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-233 means

CARC 233 covers services or charges related to the treatment of a hospital-acquired condition or preventable medical error. Payers do not want to pay extra for care needed only because something went wrong during a stay. When they identify such charges, they deny or remove them with CARC 233.

For inpatient claims, the determination often rests on the present on admission (POA) indicator reported with each diagnosis on the institutional claim. If a condition on the payer’s hospital-acquired condition list is reported as not present on admission, the payer may exclude it from DRG grouping or deny related charges. Payers may also use this code for serious reportable events and errors identified through review, and some apply it to follow-up care by physicians or other facilities under their policies.

Common causes

  • Diagnosis coded as not present on admission when it was actually present at admission.
  • Missing or unclear POA documentation, so coders chose “N” or “U.”
  • An actual hospital-acquired condition, such as a catheter-associated infection or a fall with injury during the stay.
  • Serious reportable events identified by the payer’s quality review.
  • Readmission or follow-up claims linked by the payer to the original event.

How to fix it

  1. Identify which diagnosis triggered the denial and review its POA indicator.
  2. Check the admission documentation. If the condition was present or clinically undetermined at admission and the record supports it, correct the POA indicator and submit a corrected claim.
  3. If the charges are unrelated to the flagged condition, appeal with records showing that.
  4. If the condition was hospital-acquired, accept the adjustment. Do not bill the patient.
  5. Loop in quality and risk management. A CO-233 claim often corresponds to an event that should also go through internal review.

How to prevent it

  • Document conditions present on admission clearly in the history and physical, including skin assessments and infection screening.
  • Train coders and CDI staff on POA reporting rules and query providers when POA status is unclear.
  • Audit claims with hospital-acquired condition diagnoses before submission.
  • Track CO-233 by unit and condition to support patient safety programs.
  • Keep claims-level edits that flag missing POA indicators, since those can lead to both rejections and CO-233 outcomes.

Specialty notes

This is primarily an inpatient hospital issue. Professional claims and post-acute providers may see it when a payer applies serious-event policies to related services, so check the payer’s policy for how far the non-payment extends.

Remark codes that may appear with CO-233

  • N434 (Missing/Incomplete/Invalid Present on Admission indicator.): The present on admission indicator was missing, incomplete, or invalid, which often drives the determination.
  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to plan policy on non-payable conditions and serious events.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): A medical necessity denial rather than a finding that care was caused by the facility.
  • CO-216 (Based on the findings of a review organization or the payer's findings.): The adjustment came from a review organization's or payer's findings, which may include quality findings.
  • CO-A8 (Ungroupable DRG.): The claim could not be grouped to a DRG.

CO-233 FAQ

What is a hospital-acquired condition?

It is a condition a patient develops during a hospital stay that was not present on admission and that is considered reasonably preventable, such as certain infections, falls with injury, or pressure injuries. Medicare and many payers limit payment for these.

Can I bill the patient for CO-233?

No. The CO group assigns responsibility to the provider. Many payer contracts and state rules also bar billing patients for care caused by preventable errors.

Can a CO-233 denial be overturned?

Yes, if the condition was actually present on admission and the POA indicator was coded wrong, or if the care was unrelated to the condition. Correct the claim or appeal with records.