What does denial code CO-19 mean?

CO-19 means the health plan considers the treatment related to a workplace injury, making it the workers' compensation carrier's responsibility. It is a redirect rather than a rejection of the care, and the balance moves to that carrier rather than to the patient.

Can I bill the patient after a CO-19 denial?

No. Patients with accepted workers' compensation claims generally carry no financial responsibility for the related treatment, and billing them is a compliance problem in most states. Pursue the workers' compensation carrier, and return to the health plan only with a written compensability denial.

CO-19: The claim belongs to a work-related injury carrier

CO-19 redirects rather than denies. The health plan is not disputing that the care happened or that it was necessary; it is saying another payer owns the claim because the injury was work-related. The operational risk is billing the patient by reflex when the health plan will not pay - workers' compensation patients generally have no financial responsibility for accepted claims, so a statement in that situation is both wrong and a compliance problem in most states.

What it means: The health plan has determined the treatment relates to a workplace injury and belongs to the workers' compensation carrier instead.
Who pays the balance: Not the patient's - the balance moves to the workers' compensation carrier or the employer, not to a patient statement.
Group code CO: Contractual Obligation - the provider absorbs the balance and cannot bill the patient

Why CO-19 happens

The encounter was flagged as work-related at registration and the health plan acted on that flag.
A diagnosis or accident indicator on the claim identified the injury as occupational.
The patient has an open workers' compensation claim and the payer cross-matched the date of service to it.
The claim was sent to the health plan first because the workers' compensation carrier was not identified at the visit.
The health plan is protecting itself pending a determination, even though the workers' compensation carrier may ultimately deny the claim.

How to fix a CO-19 denial

1
Confirm whether the injury really is work-related
Check the intake record and the clinical documentation. Patients sometimes report an injury as work-related at registration and the record does not support it, in which case the health plan should be reprocessing rather than redirecting.
2
Identify the workers' compensation carrier and claim number
Get the employer, carrier, adjuster, and claim number from the patient or the employer directly. Workers' compensation claims are rejected outright without a claim number, so this is the gating item.
3
Bill the workers' compensation carrier under its own rules
Workers' compensation runs on state fee schedules and its own filing deadlines, both usually different from the health plan's. Treat it as a separate billing track rather than a resubmission of the same claim.
4
Return to the health plan only if the carrier formally denies
If the workers' compensation carrier denies compensability in writing, send that denial to the health plan with the claim. The written denial is what reopens the health plan's obligation.

Deadlines depend on the payer

Filing limits and appeal windows for CO-19 vary by payer and often by plan type within the same payer. Look up the specific payer to see its verified deadlines and the source document they came from.

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Preventing CO-19 denials

Ask whether an injury is work-related at registration and capture the employer and carrier at the same time, not afterwards.
Route work-related encounters to a separate billing workflow so they never reach the health plan by default.
Track the state's workers' compensation filing deadline separately, since it is frequently shorter than the health plan's.

CO-19 frequently asked questions

What does denial code CO-19 mean?: CO-19 means the health plan considers the treatment related to a workplace injury, making it the workers' compensation carrier's responsibility. It is a redirect rather than a rejection of the care, and the balance moves to that carrier rather than to the patient.
Can I bill the patient after a CO-19 denial?: No. Patients with accepted workers' compensation claims generally carry no financial responsibility for the related treatment, and billing them is a compliance problem in most states. Pursue the workers' compensation carrier, and return to the health plan only with a written compensability denial.

Related denial codes

CO-22 CO-109 OA-23 CO-24

Last reviewed August 5, 2026.

Denial code explanations are original plain-English summaries written for reference and are not the official X12 code descriptions. Payer handling of any code varies by contract - always verify against the remittance advice and your payer agreement before adjusting a claim.