OA 19 denial code

Claim adjustment reason code 19. Often reported as OA 19 or CO 19.

Workers' compensation is responsible

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 19 means

The payer believes the condition is work related, so the workers' compensation carrier should pay instead.

The health plan decided the injury or illness came from the patient's job and is the workers' compensation carrier's responsibility. Health plans often exclude work related care when workers' compensation applies.

The claim usually has to go to the workers' compensation carrier first. If that carrier denies the case, the health plan may reconsider with the denial.

Group codes seen with 19

On a remittance, 19 comes after a group code. These are the ones it is most often reported with:

• OA 19 (Other Adjustment): Used for adjustments that are neither the provider's contractual write-off nor the patient's share. It often appears with coordination of benefits, for example when another payer already paid.
• CO 19 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The diagnosis or accident indicator on the claim suggested a work related injury.
• The patient told the plan or the provider the injury happened at work.
• The payer has an open workers' compensation case on file for the patient.

What to do next

1. Confirm with the patient whether the injury is work related and get the employer and claim details.
2. Bill the workers' compensation carrier with the case or claim number.
3. If the injury is not work related, correct any accident indicators and ask the health plan to reprocess.
4. Keep the workers' compensation denial or closure letter to send back to the health plan if needed.

Related codes

• 20 (reason code) Liability insurer is responsible
• 21 (reason code) No-fault insurer is responsible
• 22 (reason code) Another payer may be primary