CO-19 Denial Code: Work-Related Injury, Liability of Workers' Compensation Carrier
CO-19 means this is a work-related injury or illness and thus the liability of the Workers' Compensation carrier — the health plan is directing the claim to workers' comp instead. It carries the CO group code, so the amount is not patient responsibility; the fix is to bill the correct workers' comp carrier, not the patient.
- Group
- CO — Contractual Obligation
- Category
- Workers' compensation liability
- Appealable?
- Yes — when the injury was not work-related
- Typical fix
- Bill the workers' comp carrier, or appeal with proof it was not work-related
What does denial code CO-19 mean?
CO-19 is the health plan redirecting the claim to workers\' compensation. The official X12 description is "This is a work-related injury/illness and thus the liability of the Worker\'s Compensation Carrier." The payer believes the condition arose from work, so the WC carrier — not the health plan — is responsible. Because it carries the CO group code, the amount is a contractual obligation and cannot be billed to the patient.
It is a liability and payer-routing issue, not a coverage or benefit denial on merits. The claim goes to the correct carrier rather than being written off or shifted to the patient.
Why does CO-19 happen?
- Work injury diagnosis — the diagnosis or injury code signals an occupational cause.
- Open WC record — the payer has an active workers\' comp file linking this condition to the patient.
- Prior WC claim — an earlier claim for the same injury was routed to workers\' comp.
- Misapplied flag — a non-work-related injury coded in a way that suggested an occupational cause.
Mini-example: 99283 (emergency visit) billed at $310 to a commercial health plan for a back injury the payer has flagged as work-related. The plan returns CO-19. If it truly was a workplace injury, billing the workers\' comp carrier with the WC claim number collects the $310; if it was a home injury, an appeal with records reroutes it to the health benefit.
How do you work a CO-19?
- Confirm with the patient and employer whether the injury was genuinely work-related.
- If it was, obtain the workers\' comp claim number, adjuster, and carrier and bill workers\' comp under their rules.
- If it was not work-related, appeal to the health plan with a provider statement or records establishing the true cause.
- Track the timely filing window for both the health plan and the WC carrier so neither closes during the handoff.
How do you prevent CO-19?
Screen for work-relatedness at registration and capture workers\' comp details up front when an injury is occupational, so the first claim goes to the right carrier. Code injuries accurately so a non-work-related condition is not flagged as occupational. Coordinate payer records to keep coordination of benefits and any WC files aligned, and route unfamiliar liability denials through the denial code lookup to separate CO-19 from other-payer situations like CO-16.
Frequently asked questions
No. CO-19 carries the CO group code, so the amount is a contractual obligation, not patient responsibility. The health plan is saying a workers' compensation carrier is liable because the injury is work-related. The remedy is to bill the correct workers' comp carrier, not to shift the balance to the patient.
The diagnosis or a prior claim may have flagged the condition as work-related, or the payer has an open workers' comp record on the patient. An E-code or injury diagnosis suggesting an occupational cause can trigger it. If the injury was not work-related, appeal with documentation clarifying the true cause.
If it truly is a work injury, obtain the workers' comp claim number, adjuster, and carrier from the employer and bill workers' comp directly under their rules. If it is not work-related, appeal to the health plan with a provider statement or records establishing the non-occupational cause so the health benefit applies.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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