CO-157: Service Denied — Provided Due to Act of War
The payer applied the act-of-war exclusion. You cannot bill the patient. Correct any coding errors and resubmit, or appeal if the payer misinterpreted the circumstances.
What Does CO-157 Mean?
CO-157 is the standard pairing for this code. The CO designation indicates the act-of-war exclusion is a contractual provision — the payer is denying coverage based on the plan's terms, and the provider cannot bill the patient for the denied amount. In most cases, this is a coding error that can be corrected by removing war-related codes and resubmitting. If the denial is correct and the patient lacks alternative coverage, the provider must write off the amount.
CARC 157 is a rare and highly specific denial code that appears when the payer has determined the service or procedure was provided as a result of an act of war. Nearly all standard health insurance plans include an act-of-war exclusion clause that allows the insurer to deny coverage for medical services resulting from war, military action, or armed conflict.
In practice, this denial is uncommon in domestic civilian billing. When it does appear, the most frequent cause is a coding error — a billing staff member inadvertently used a code, modifier, or external cause code that indicated the service was related to an act of war when it was not. The second scenario is payer misinterpretation, where the diagnosis codes, location information, or circumstances documented in the claim led the payer to incorrectly conclude the service was war-related. Less commonly, the denial correctly applies to a civilian health plan when the patient received care for injuries genuinely caused by a war-related event.
The critical first step is determining whether the denial is correct. If it is a coding error, the fix is straightforward — correct the codes and resubmit. If the payer misinterpreted the circumstances, an appeal with documentation proving the service was not war-related should resolve it. If the service was genuinely provided due to an act of war and the patient has military or government coverage (TRICARE, VA benefits, Defense Health Agency), those programs may provide coverage that civilian plans do not.
Common Causes
| Cause | Frequency |
|---|---|
| Service correctly identified as resulting from an act of war The medical service was genuinely provided to treat injuries or conditions directly caused by an act of war, and the payer applied the war exclusion clause found in most standard health insurance policies | Most Common |
| Coding error — service incorrectly coded as war-related The provider's billing staff mistakenly used a code or modifier that indicated the service was related to an act of war when it was not, triggering the exclusion in error | Common |
| Payer misinterpretation of the service circumstances The payer incorrectly concluded that the service was war-related based on incomplete information, geographic location, or diagnosis codes, when the actual circumstances did not involve an act of war | Common |
| Documentation gaps about the circumstances of injury The clinical records do not clearly document the cause or circumstances of the patient's condition, leading the payer to apply the war exclusion based on ambiguous information | Occasional |
How to Resolve
Determine whether the denial was triggered by a coding error, payer misinterpretation, or an actual act-of-war situation, then take the appropriate corrective action.
- Check for war-related coding errors Review the claim for any ICD-10 external cause codes (Y36 series), modifiers, or diagnosis codes that triggered the war exclusion. Determine if these codes were applied in error.
- Correct codes and resubmit If the coding was incorrect, remove the war-related codes, apply the correct codes, and resubmit.
- Appeal with circumstance documentation If the codes were correct but the payer misinterpreted the circumstances, appeal with medical records and provider statements clarifying that the service was not related to an act of war.
- Pursue alternative coverage if applicable For genuine war-related services, assist the patient in filing claims with TRICARE, VA, or applicable government programs.
Common RARC Pairings
The RARC code tells you exactly what triggered the CO-157:
| RARC | Description |
|---|---|
| N381 | Alert: The service or procedure is not covered under the patient's plan due to policy exclusions |
How to Prevent CO-157
- Train coding staff on the proper use of ICD-10 external cause codes, particularly the Y36 series related to operations of war
- Implement coding review checks that flag claims containing war-related codes before submission
- Document the cause and circumstances of injuries clearly in the medical record to prevent payer misinterpretation
- Audit billing practices regularly to identify patterns of incorrect external cause code usage
General Prevention
- Train billing staff to understand the specific coding requirements related to act-of-war exclusions and avoid inadvertently triggering this denial
- Implement a review process for claims that involve trauma or injuries in conflict zones to ensure proper coding and documentation of the circumstances
- Document the cause and circumstances of injury clearly in the medical record so payers do not misinterpret the situation as war-related
- Conduct regular audits of billing practices to identify any patterns of incorrect war-related coding
- Maintain awareness of payer-specific definitions of 'act of war' and how they apply to various clinical scenarios
Also Filed As
The same CARC 157 may appear with different Group Codes:
Related Denial Codes
Sources
- https://www.mdclarity.com/denial-code/157
- https://docs.claim.md/docs/claim-adjustment-reason-codes
- Codes maintained by X12. Visit x12.org for official definitions.