OA 21 denial code
Claim adjustment reason code 21. Often reported as OA 21 or CO 21.
No-fault insurer 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 .
What 21 means
The payer says a no-fault policy, often auto insurance, should pay for this injury before the health plan.
The injury appears to fall under no-fault coverage, most often personal injury protection on an auto policy. The health plan expects that coverage to pay first.
Once the no-fault benefits are exhausted or denied, the health plan may process the claim when you send the no-fault payer's explanation of benefits.
Group codes seen with 21
On a remittance, 21 comes after a group code. These are the ones it is most often reported with:
- OA 21 (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 21 (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 claim showed an auto accident indicator or an accident related diagnosis.
- The patient reported a motor vehicle accident to the plan.
- The payer's records show no-fault coverage on file for the injury.
What to do next
- Get the auto or no-fault carrier details and claim number from the patient.
- Bill the no-fault carrier first and keep its payment or denial explanation.
- Send the no-fault explanation of benefits to the health plan when benefits are exhausted or denied.
- Correct the accident indicators if the injury was not related to an accident.
Related codes
- 19 (reason code) Workers' compensation is responsible
- 20 (reason code) Liability insurer is responsible
- 22 (reason code) Another payer may be primary
Source
Official wording: X12 Claim Adjustment Reason Codes list. The explanation on this page is our own plain-English wording, not the X12 text.
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