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CO-P8 Denial Code: P&C Claim Under Investigation

CO-P8 means a property and casualty carrier has put the claim on hold or denied payment because the underlying claim (the injury, accident, or coverage) is still under investigation. Payment decisions wait until the investigation ends.

Quick facts

Code
CO-P8 (CARC P8)
Status
Active In use since November 1, 2013; last modified July 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The carrier isn't paying for now; state rules often limit billing the claimant while an investigation is pending.
  • OA (Other Adjustment): Some carriers use OA because responsibility hasn't been decided yet.
Official description
Claim is under investigation. Usage: If adjustment is at the Claim Level, the payer must send and the provider should refer to the 835 Insurance Policy Number Segment (Loop 2100 Other Claim Related Information REF qualifier 'IG') for the jurisdictional regulation. If adjustment is at the Line Level, the payer must send and the provider should refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment information REF). To be used for Property and Casualty only.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-P8 means

CARC P8 says claim is under investigation. X12 limits it to property and casualty claims and requires the carrier to cite the jurisdictional regulation in the 835 (loop 2100 REF qualifier IG for claim-level adjustments, loop 2110 REF for line-level). It replaced deactivated CARC 221.

In workers’ compensation and auto claims, the carrier has to decide whether the injury is covered before it pays medical bills. It may be checking how the accident happened, whether the policy was in force, whether the person was covered, or whether the injury is related to the reported event. Until it decides, bills are held or denied with CO-P8.

Common causes

  • New claim not yet accepted by the carrier.
  • Disputed facts about how or where the injury occurred.
  • Coverage questions, such as whether the policy was active or the claimant is an eligible person.
  • Missing claimant paperwork, such as an application for benefits.
  • Suspected fraud or misrepresentation under review.
  • Relatedness questions about whether a service is tied to the accepted injury.

How to handle it

  1. Contact the adjuster to confirm the investigation, what it covers, and the expected timeline.
  2. Send any requested records or reports promptly.
  3. Tell the patient they may need to cooperate with the carrier, for example by completing forms.
  4. Track the claim with follow-up dates and state deadlines.
  5. Rebill or appeal once the carrier decides. If it denies, get the written determination and move to other coverage.
  6. Check state rules before billing the claimant during the investigation.

How to prevent problems

  • Collect claim details at intake: carrier, claim number, adjuster, date of injury, and employer or policy information.
  • Confirm claim status before scheduling extended treatment.
  • Keep health plan information on file as a backup.
  • Document the mechanism of injury clearly in the first visit note.

Specialty notes

Emergency and urgent care providers often treat before any P&C claim is filed, so their first bills commonly hit CO-P8. Orthopedic and PT practices should confirm acceptance before long treatment plans.

Remark codes that may appear with CO-P8

  • N581 (Investigation of coverage eligibility is pending.): Investigation of coverage eligibility is pending.
  • N675 (Additional information is required from the injured party.): Additional information is required from the injured party.
  • N582 (Benefits suspended pending the patient's cooperation.): Benefits are suspended pending the patient's cooperation.
  • CO-221Deactivated (Claim is under investigation.): The deactivated code that CARC P8 replaced.
  • CO-P4 (Workers' Compensation claim adjudicated as non-compensable.): The workers' comp claim was found non-compensable, a possible outcome of an investigation.
  • OA-P11 (The disposition of the related Property & Casualty claim (injury or illness) is pending due to litigation.): Disposition pending due to litigation, rather than investigation.
  • OA-133 (The disposition of this service line is pending further review. (Use only with Group Code OA).): The service line is pending further review, used outside P&C.

CO-P8 FAQ

How long can a P&C investigation take?

It depends on the state and the type of claim. Many states set time limits for carriers to accept or deny workers' comp and no-fault claims. Ask the adjuster for the expected timeline.

Should I bill the patient's health plan while the claim is under investigation?

Some practices do, especially when filing limits are a concern, but the health plan may deny it as work- or accident-related. Know each plan's rules and keep the carrier's investigation notice.

What should I send the carrier?

Whatever it asks for, often records, reports, or claimant forms. Missing information can extend the investigation.

Is CO-P8 a final denial?

No. It reflects a pending status. Once the investigation ends, the carrier should pay, deny with a different code, or request more information.

Where does the carrier cite the regulation for CO-P8?

At claim level, in the 835 insurance policy number segment (loop 2100 REF, qualifier IG). At line level, in the healthcare policy identification segment (loop 2110 REF).