UB04 Field 67: Principal Diagnosis Code

Overview

Field 67 (Principal Diagnosis Code) on the UB-04 claim form is a required field for both inpatient and outpatient hospital claims. This field captures the ICD diagnosis code that represents the condition established after study to be chiefly responsible for the patient's admission to the hospital. ^[1] The code entered must be the full ICD diagnosis code, including all applicable digits—five digits for ICD-9 or seven digits for ICD-10. The decimal point between the third and fourth digit is implied and should not be reported. ^[2] This field is critical for accurate diagnosis coding, reimbursement determination, and quality reporting.

When to Use

The field is used when the patient has a confirmed diagnosis that meets the definition of principal diagnosis—the condition chiefly responsible for the encounter. Providers should use this field for all claim types including Medicare, Medicaid, and commercial insurance submissions.

Step-by-Step Claim Example

Scenario: A 65-year-old patient is admitted to the hospital with chest pain and shortness of breath. After evaluation, the physician determines the patient has acute myocardial infarction (heart attack) as the principal diagnosis.

Step 1: Identify the principal diagnosis code.

Step 2: Enter the full code in Field 67. Write "I213" (without the decimal point, as it is implied). Ensure all seven characters are present if required—for I21.3, the code is complete with four characters, but verify the specific code's length requirements.

Step 3: Add the Present on Admission (POA) indicator. Since the heart attack was present when the patient was admitted, enter "Y" in the POA field. ^[1]

Step 4: Verify the code matches the medical record documentation. The principal diagnosis must be supported by the physician's final diagnosis and clinical findings.

Step 5: Submit the claim. The completed Field 67 will read: "I213" with POA indicator "Y".

Common Mistakes & Audit Red Flags

Mistake 1: Using an incomplete code. Entering only three or four digits when the code requires five or seven digits is a frequent error. For ICD-10, many codes require seven characters. ^[2] This can lead to claim rejection or denial.

Mistake 2: Including the decimal point. The decimal between the third and fourth digit is implied and should not be entered. Entering "I21.3" instead of "I213" may cause processing errors.

Mistake 3: Missing or incorrect POA indicator. For inpatient claims, failing to report the POA indicator or using an incorrect value (e.g., "N" when the condition was present on admission) is a major audit red flag. ^[1]

Mistake 4: Using a code that does not match the medical record. The principal diagnosis must be clearly documented by the attending physician. Using a code not supported by documentation is a compliance risk.

Audit Red Flags: Claims with missing POA indicators, codes that do not match the patient's condition, or codes that are truncated or incorrectly formatted are flagged for review. Payers may deny payment or request additional documentation.

Related Codes/Fields

Field Number	Field Name	Description	Relationship to Field 67
FL 66	Diagnosis and Procedure Code Qualifier (ICD Version Indicator)	Indicates whether ICD-9 or ICD-10 codes are used	Must match the version used in Field 67
FL 67 a-q	Other Diagnosis Codes	Additional diagnoses that coexist at the time of admission	Comorbid conditions that support the principal diagnosis
FL 69	Admitting Diagnosis	The diagnosis at the time of admission	May differ from principal diagnosis after study
FL 70 a-q	Patient’s Reason for Visit Code	Codes for outpatient visits	Used for outpatient claims when principal diagnosis is not yet established
FL 72 a-c	External Cause of Injury Code (E-Code)	Codes for external causes of injury	Used when principal diagnosis is injury-related
FL 74	Principal Procedure Code and Date	The principal procedure performed	Related to the principal diagnosis when surgery is performed

^[1]

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References

[1] Maryland Medicaid — FL 67 — https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf

[2] CMS Chapter 25 — FL 67 — https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c25.pdf