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CO-P21 Denial Code: Denied Under MPC or PIP Rules

CO-P21 means an auto insurer denied payment based on the jurisdictional regulations or payment policies for Medical Payments Coverage (MPC) or Personal Injury Protection (PIP) benefits. The cited regulation and remark codes explain which rule applied.

Quick facts

Code
CO-P21 (CARC P21)
Status
Active In use since November 1, 2013; last modified March 1, 2018.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The auto carrier won't pay; state no-fault rules decide whether the claimant or another payer can be billed.
  • PR (Patient Responsibility): Used when the carrier indicates the patient is responsible, for example when the policy has no PIP or MPC. Consider the patient's health plan first.
Official description
Payment denied based on the Medical Payments Coverage (MPC) and/or Personal Injury Protection (PIP) Benefits jurisdictional regulations, or payment policies. 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') if the jurisdictional regulation applies. 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) if the regulations apply. To be used for Property and Casualty Auto only.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-P21 means

CARC P21 says payment denied based on the Medical Payments Coverage (MPC) and/or Personal Injury Protection (PIP) benefits jurisdictional regulations, or payment policies. X12 limits it to property and casualty auto claims. It replaced deactivated CARC Y1.

Auto medical benefits are governed by the policy and by state law. No-fault states have detailed PIP rules on who qualifies, what must be filed, deadlines, examinations, and limits. When an auto carrier denies a medical bill under those rules, it uses P21 and cites the regulation.

This is the auto-specific counterpart to CO-21. CO-21 is a health plan saying the auto carrier should pay; CO-P21 is the auto carrier saying it won’t.

Common causes

  • No PIP or MPC coverage on the policy on the date of loss (N651).
  • Claimant didn’t file an application for benefits or an assignment of benefits.
  • Missed independent medical exam or examination under oath.
  • Late notice or late billing under state no-fault deadlines.
  • Claimant not an eligible injured person, such as a non-occupant under some policies.
  • Service unrelated to the accident.

How to fix it

  1. Read the remark codes and cited regulation.
  2. If paperwork is missing, help the claimant complete it and resubmit if state rules allow.
  3. If the carrier’s facts are wrong, request reconsideration with documentation.
  4. Use the state’s dispute process, such as arbitration in some no-fault states, within its deadlines.
  5. Bill other coverage, usually the health plan, with the auto denial attached.
  6. Check state rules before billing the patient.

How to prevent it

  • Collect auto policy, claim number, and adjuster details at the first visit.
  • Confirm PIP or MPC coverage and remaining limits before treatment.
  • Tell claimants about required forms and exams.
  • Track no-fault deadlines for notices and bills by state.

Specialty notes

Chiropractic, PT, and orthopedic practices in no-fault states handle the most PIP claims and benefit from a dedicated auto claim workflow.

Remark codes that may appear with CO-P21

  • N651 (No Personal Injury Protection/Medical Payments Coverage on the policy at the time of the loss.): No PIP or medical payments coverage on the policy at the time of the loss.
  • N594 (Records reflect the injured party did not complete an Application for Benefits for this loss.): The injured party didn't complete an application for benefits.
  • N593 (Not covered based on failure to attend a scheduled Independent Medical Exam (IME).): Not covered because the claimant didn't attend a scheduled independent medical exam.
  • N587 (Policy benefits have been exhausted.): Policy benefits have been exhausted.
  • CO-Y1Deactivated (Payment denied based on Medical Payments Coverage (MPC) or Personal Injury Protection (PIP)): The deactivated code that CARC P21 replaced.
  • CO-P22 (Payment adjusted based on the Medical Payments Coverage (MPC) and/or Personal Injury Protection (PIP)): Payment adjusted, rather than denied, under MPC or PIP rules.
  • CO-P23 (Medical Payments Coverage (MPC) or Personal Injury Protection (PIP)): An MPC or PIP jurisdictional fee schedule adjustment.
  • CO-21 (This injury/illness is the liability of the no-fault carrier.): A health plan says a no-fault carrier is responsible, the other side of the same situation.

CO-P21 FAQ

What are MPC and PIP?

Medical Payments Coverage and Personal Injury Protection are auto insurance coverages that pay medical expenses for people injured in a vehicle accident, often regardless of fault. PIP is required in some states and optional in others.

Where do I bill after CO-P21?

Usually the patient's health plan, with the auto carrier's denial attached, since health plans often deny accident claims until the auto coverage is resolved.

Where is the regulation cited?

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), when regulations apply.

Is CO-P21 used for workers' comp?

No. X12 limits it to property and casualty auto claims.

Can a CO-P21 denial be reversed?

Yes, when it's based on something correctable, such as a missing application or form. Denials for no coverage or exhausted benefits usually aren't reversed.