UB04 Field 72: External Cause of Injury Code

Overview

Field 72 of the UB‑04 form – “External Cause of Injury Code” (ECI) – is not a required field for inpatient or outpatient claims. According to the CMS Chapter 25 instructions, this field is explicitly “Not used” and any data entered into it “will be ignored.” ^[1] Maryland Medicaid reinforces that the eighth digit (the Present on Admission indicator) of FL 72 is not required, and that the field itself is part of the three ECI fields on the form. ^[2] Providers should understand that while the UB‑04 layout includes this box for possible external cause coding, current federal and state billing guidance treats it as dormant; submitted codes will not be processed and do not affect payment determinations.

When to Use

The External Cause of Injury Code field (Box 72) should not be used under current billing rules. CMS explicitly states that data entered in FL 72 will be ignored, meaning there is no operational requirement to populate it for any claim type. ^[1] Maryland Medicaid similarly notes that the Present on Admission indicator is not required for FL 72, and the field itself is not designated as mandatory in any billing situation. ^[2] Therefore, neither inpatient nor outpatient claims require completion of this field. Providers should leave Box 72 blank on all UB‑04 submissions to avoid unnecessary data entry that offers no reimbursement or clinical value.

Step-by-Step Claim Example

Because Field 72 is not used, a proper claim example demonstrates leaving it blank:

1. Prepare the UB‑04 form – Fill all required fields for the claim (e.g., patient name, health plan ID, admission date, principal diagnosis in Box 67).
2. Locate Box 72 – It is found in the “Diagnosis Codes” section of the form, alongside other diagnosis and external cause fields.
3. Do not enter any code – According to CMS, any ICD‑10‑CM code placed in this box will be ignored by the processing system. ^[1] Maryland Medicaid confirms that the field is not required and the POA indicator is not needed. ^[2]
4. Proceed to required fields – Complete Box 74 (Principal Procedure) if an inpatient procedure was performed, and other required fields.
5. Submit – The claim will be accepted without any data in FL 72.

For example, a patient admitted after a fall: the external cause code (e.g., W01.0XXA) would normally be placed in FL 72, but since the field is ignored, the code should instead be reported in a secondary diagnosis field (Box 67A–Q) if it affects the stay, per official coding guidelines. The Maryland Medicaid document permits “E codes” in other diagnosis fields where appropriate. ^[2]

Common Mistakes & Audit Red Flags

• Entering an external cause code in FL 72 – A frequent error is assuming the field must be completed for injury claims. CMS warns that data entered will be ignored, but the act of entering it wastes time and may trigger internal edits if a provider’s system flags it as unusual. ^[1]
• Including a POA indicator in the eighth digit – Maryland Medicaid states that the POA indicator is not required for FL 72. Even if a value is entered, the field will not be processed. ^[2]
• Confusing with principal diagnosis – Providers sometimes place an external cause code in FL 72 and incorrectly omit it from the secondary diagnosis fields. The principal diagnosis field (Box 67) cannot accept “E codes” per the Maryland document. ^[2] The external cause should be reported in a co-morbidity field (Box 67A–Q) if it coexists and affects treatment or length of stay.
• Audit focus – While FL 72 itself will not be audited because it is ignored, payers may review secondary diagnosis fields for completeness of external cause coding. Leaving FL 72 blank is correct, but failing to report external cause codes elsewhere when clinically relevant could lead to under‑coding.

Related Codes/Fields (markdown table)

Field/Code	Relationship to FL 72	Source
FL 67 – Principal Diagnosis	Principal diagnosis must be an ICD‑10‑CM code; “E codes” (external cause) are not acceptable here. External cause codes belong in secondary fields.	[2]
FL 67A–Q – Other Diagnosis Codes	These fields may accept “V codes” and “E codes” where appropriate, serving as the correct location for external cause codes that affect the stay.	[2]
FL 73 – Reserved	Also marked as “Not used” by CMS; data entered will be ignored. Sibling field to FL 72.	[1]
FL 69 – Admitting Diagnosis	Not required; uses ICD‑10‑CM diagnosis code for admitting condition. No direct link to external cause codes, but external cause may be related to the admitting diagnosis.	[2]
ICD‑10‑CM E Codes	These are the codes that would be placed in FL 72 if it were active. They are reported elsewhere based on current guidance.	[1]

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References

[1] CMS Chapter 25 — FL 72 — https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c25.pdf

[2] Maryland Medicaid — FL 72 — https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf