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CO-157 Denial Code: Service Resulted From an Act of War

CO-157 means the payer denied the service because it was provided as a result of an act of war, which many health plans exclude. The claim may belong with another program, such as military or veterans coverage, or may be a coding error.

Quick facts

Code
CO-157 (CARC 157)
Status
Active In use since September 30, 2003; last modified September 30, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The payer excludes the service and treats the amount as the provider's adjustment for this payer. It does not by itself mean another payer or the patient owes it.
  • PR (Patient Responsibility): The payer indicates the patient is responsible because the plan excludes war-related care. Check whether another coverage source applies before billing the patient.
Official description
Service/procedure was provided as a result of an act of war.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-157 means

CARC 157 reads “Service/procedure was provided as a result of an act of war.” Many health plans and insurance policies contain a war exclusion: they do not pay for injuries or illnesses caused by war or military operations. When the payer identifies the claim as war-related, it applies CO-157.

The payer usually learns this from the claim itself, for example ICD-10-CM external cause codes in the Y36 or Y37 categories (war operations and military operations), or from an accident or injury questionnaire the patient returned.

Example: a veteran is treated for a condition documented as a late effect of a blast injury sustained in a war zone. The external cause code on the claim triggers the commercial plan’s war exclusion, and the claim comes back CO-157.

Common causes

  • External cause codes indicating war or military operations reported in box 21.
  • Patient questionnaire responses describing the injury as war-related.
  • Plan exclusions that apply even for conditions treated long after the original event.
  • Coding errors, such as selecting a war-operations external cause code when a different mechanism applies.

How to fix it

  1. Review the diagnosis and external cause codes. Confirm the record really describes a war-related cause.
  2. If coding was wrong, submit a corrected claim (resubmission code 7 in box 22) with accurate codes.
  3. If it is war-related, ask the patient about military or veterans coverage. TRICARE, VA community care, or another program may be the appropriate payer, often with their own authorization rules.
  4. Read the plan’s exclusion language. If the exclusion does not clearly apply to the patient’s situation, file an appeal quoting the plan document.
  5. Only bill the patient if the payer’s response or plan terms support patient responsibility and no other coverage applies.

How to prevent it

  • Ask about military service and other coverage at registration, and record it in the coordination of benefits fields (box 9 to 9d, 11d). See eligibility and COB denials.
  • Code external causes carefully, and only when documentation supports them.
  • Verify VA or TRICARE authorization before treating patients whose care those programs manage.
  • Flag unusual exclusion codes in your remittance review so staff know to redirect rather than rebill.

Remark codes that may appear with CO-157

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): The payer is pointing to plan documents for the exclusion language.
  • CO-159 (Service/procedure was provided as a result of terrorism.): Similar exclusion, but for injuries resulting from terrorism.
  • CO-160 (Injury/illness was the result of an activity that is a benefit exclusion.): A broader exclusion for injuries from an excluded activity.
  • CO-158 (Service/procedure was provided outside of the United States.): Services provided outside the United States, another uncommon exclusion.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): A general statement that the service is not covered under the benefit plan.

CO-157 FAQ

Is CO-157 common?

No. Most practices will rarely see it. When it appears, it usually follows a diagnosis or external cause code indicating a war operation, or information from the patient's accident questionnaire.

Who pays for war-related injuries?

It depends on the patient. Active-duty service members and many veterans have coverage through TRICARE or the VA, which may be the right payer. Otherwise the plan's exclusion determines whether the patient is responsible.

What if the war-related coding was a mistake?

Correct the diagnosis or external cause codes and submit a corrected claim with resubmission code 7. The payer should then adjudicate normally.

Does CO-157 apply to conditions diagnosed years after military service?

It can, if the plan's exclusion covers conditions resulting from war regardless of when they are treated. Read the exact exclusion wording, because some plans limit it to injuries sustained during active hostilities.