Patient was admitted as an inpatient on a provisional diagnosis (Updated for 2026)

Common Causes for CO-120

Denials with code CO-120 typically happen for the following specific reasons:

• Billing the inpatient claim with a preliminary, working, or 'rule out' diagnosis instead of the definitive principal diagnosis established by the end of the hospital stay.
• Incomplete clinical documentation where the attending physician failed to specify the final resolved diagnosis in the discharge summary.
• The provisional admitting diagnosis did not meet inpatient medical necessity criteria under standard utilization review guidelines such as InterQual or Milliman Care Guidelines (MCG).
• A mismatch between the admitting provisional diagnosis on the UB-04 claim form and the actual clinical evidence supported in the medical chart.

How to Prevent CO-120 Denials

To avoid receiving this denial in the future, implement these specific checks:

• Deploy a robust Clinical Documentation Improvement (CDI) protocol to query physicians for diagnostic clarification prior to patient discharge.
• Ensure coding teams strictly adhere to the ICD-10-CM Official Guidelines for Coding and Reporting, specifically selecting the condition 'established after study' as the principal diagnosis.
• Utilize utilization management staff to continuously assess the clinical necessity of provisional admissions within the first 24 to 48 hours to ensure criteria for inpatient status are fully met and documented.
• Conduct comprehensive pre-billing audits on inpatient claims to verify that provisional admitting diagnoses have been updated to definitive codes backed by pathology, radiology, or lab results.

Appeal Letter Template for CO-120

If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.

[Your Practice Header]
[Date]

[Payer Name]
[Appeals Department Address]

RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: CO-120 - Patient was admitted as an inpatient on a provisional diagnosis

Dear Appeals Department,

I am writing to appeal the denial of the above-referenced claim, which was denied with code CO-120: "Patient was admitted as an inpatient on a provisional diagnosis".

We are formally appealing the denial of this inpatient claim (Denial Code CO-120). While the patient was initially admitted under a provisional diagnosis to ensure immediate, medically necessary intervention, a definitive diagnosis was established after study during the course of the inpatient stay, as fully documented in the enclosed discharge summary. Pursuant to the ICD-10-CM Official Guidelines for Coding and Reporting, the principal diagnosis is defined as 'that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.' The submitted clinical documentation clearly outlines that the patient's presenting symptoms, severity of illness, and subsequent diagnostic workup required acute inpatient level of care, satisfying both CMS guidelines and standard medical necessity criteria. We have attached the complete medical record, including diagnostic test results and the final discharge summary, to substantiate the coded principal diagnosis and request that this denial be overturned and the claim processed for immediate payment.

Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].

We respectfully request that you reprocess this claim for payment.

Sincerely,

[Your Name]
[Title]
[Practice Name]