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OA-19 Denial Code: Work-Related Injury, Bill Workers' Comp

OA-19 means the health plan decided the injury or illness is work-related, so the workers' compensation carrier is responsible rather than the patient's health plan. Identify the workers' comp claim and carrier and bill them; if it isn't work-related, correct the claim or appeal.

Quick facts

Code
OA-19 (CARC 19)
Status
Active In use since January 1, 1995; last modified September 30, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • OA (Other Adjustment): The common group. Neither provider nor patient is assigned the amount; the claim belongs with the workers' compensation carrier.
  • CO (Contractual Obligation): Some payers use CO. The provider cannot bill the patient for it and should pursue the workers' comp carrier.
  • PR (Patient Responsibility): Occasionally used, but workers' comp rules in many states limit billing injured workers for covered work injuries. Check state rules before billing the patient.
Official description
This is a work-related injury/illness and thus the liability of the Worker's Compensation Carrier.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What OA-19 means

CARC 19 says this is a work-related injury or illness and thus the liability of the workers’ compensation carrier. Group health plans generally exclude injuries covered by workers’ compensation. When the payer sees signs that the condition is work-related, it denies the claim and expects you to bill the workers’ comp carrier.

Signals the payer may use include box 10a (employment-related) checked yes, diagnosis and external cause codes that suggest a workplace injury, a member questionnaire, or a report from the carrier that it has accepted responsibility for the condition, which Medicare communicates with N728.

Common causes

  • Box 10a marked yes, intentionally or by mistake.
  • An open workers’ comp claim reported to the health plan for the same diagnosis.
  • Patient answered an accident questionnaire saying the injury happened at work.
  • Diagnosis or external cause codes that suggest an occupational injury.
  • Intake didn’t ask how the injury happened, so the workers’ comp carrier was never identified.

How to fix it

  1. Confirm the facts with the patient. Did the injury or illness arise from work?
  2. If it’s work-related, get the employer, carrier, claim number, date of injury, and adjuster contact, then bill the workers’ comp carrier using its required format and forms.
  3. If it’s not work-related, correct box 10a and any related information, send a corrected claim (resubmission code 7 in box 22), and have the patient confirm with the plan if needed.
  4. If workers’ comp denies, send the carrier’s determination to the health plan and request reprocessing or appeal.
  5. Follow state rules before billing the patient; many states restrict balance billing injured workers for accepted claims.

How to prevent it

  • Ask about injury cause at intake and record the date of injury, employer, and any claim number.
  • Complete box 10a accurately on every claim.
  • Set up workers’ comp as a separate case in your system so claims go to the right payer.
  • Verify coverage early. See eligibility and COB denials for how liability and coordination problems cause denials.

Specialty notes

Orthopedics, PT/OT, chiropractic, and occupational medicine see OA-19 most. Workers’ comp claims often have their own fee schedules, treatment guidelines, and authorization rules that differ from the health plan’s, so confirm those before continuing treatment under the comp claim.

Remark codes that may appear with OA-19

  • N728 (A workers' compensation insurer has reported having ongoing responsibility for medical services (ORM) for this diagnosis.): A workers' compensation insurer has reported ongoing responsibility for medical services for this diagnosis.
  • MA92 (Missing plan information for other insurance.): Missing plan information for other insurance, here the workers' compensation carrier.
  • CO-P2 (Not a work related injury/illness and thus not the liability of the workers' compensation carrier): The reverse situation: the workers' comp carrier says the injury is not work-related.
  • CO-P4 (Workers' Compensation claim adjudicated as non-compensable.): The workers' comp claim was found non-compensable, which may send the claim back to the health plan.
  • CO-20 (This injury/illness is covered by the liability carrier.): The liability carrier is responsible instead of the health plan.
  • CO-21 (This injury/illness is the liability of the no-fault carrier.): The no-fault carrier is responsible, typical after auto accidents.
  • OA-22 (This care may be covered by another payer per coordination of benefits.): Another payer may be primary under coordination of benefits.

OA-19 FAQ

What do I need to bill workers' comp after an OA-19?

Typically the employer, the workers' comp carrier, the claim number, the date of injury, and the adjuster's contact information. Carriers may also require specific reports or forms under state rules.

What if the patient says the injury isn't work-related?

Confirm the facts with the patient, correct box 10a if it was marked wrong, and ask the health plan to reprocess. If the payer's records show a workers' comp claim, the patient may need to confirm with the plan that the injury is unrelated.

What if workers' comp denies the claim too?

Get the carrier's denial, such as a non-compensable determination, and send it to the health plan with the claim. Many plans will then process it.