OA P8 denial code

Claim adjustment reason code P8. Often reported as OA P8 or CO P8.

Claim under investigation

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 P8 means

The property and casualty payer is investigating the claim and is holding or denying payment until that ends.

Property and casualty payers, including workers' compensation and auto carriers, are the only ones that use it. The carrier has not reached a decision on liability or coverage yet. Common reasons include questions about how the injury happened or whether the policy applies.

A rule reference may come with it on the remittance. Expect the claim to be revisited once the investigation ends, and keep track of filing deadlines while you wait.

Group codes seen with P8

On a remittance, P8 comes after a group code. These are the ones it is most often reported with:

• OA P8 (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 P8 (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 carrier is still determining whether the injury is covered.
• Records or statements needed for the investigation are outstanding.
• There are questions about the accident or injury circumstances.

What to do next

1. Contact the adjuster for the status and expected timeline of the investigation.
2. Send any records the adjuster requests promptly.
3. Follow up on a schedule and resubmit or request reprocessing when the decision is made.
4. Consider other coverage if the investigation goes on for a long time, following the payer's rules.

Related codes

• P4 (reason code) Workers' comp claim found non-compensable
• P6 (reason code) Based on entitlement to benefits
• P10 (reason code) Payment held at zero during a lawsuit