CO P28 denial code
Claim adjustment reason code P28. Often reported as CO P28 or PR P28.
Adjusted under auto liability rules
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 P28 means
The auto insurer reduced payment under its liability coverage regulations or policies.
It is limited to auto insurance medical claims. The liability carrier paid part of the claim but reduced it based on a liability policy term or regulation, such as a limit.
Fee schedule reductions under liability coverage use P29, so P28 usually points to a policy or rule limit.
Group codes seen with P28
On a remittance, P28 comes after a group code. These are the ones it is most often reported with:
- CO P28 (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.
- PR P28 (Patient Responsibility): The amount is assigned to the patient. Deductibles, coinsurance and copays are the everyday examples. Whether you can collect it still depends on your contract and the patient's plan.
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 liability policy limit was reached for the injured person.
- A regulation limits what the liability carrier pays for the service.
- The payer applied a comparative fault reduction.
What to do next
- Ask the adjuster which policy term caused the reduction.
- Bill any other coverage for the remaining balance.
- Follow state rules before pursuing the patient for the difference.
Related codes
- P27 (reason code) Denied under auto liability rules
- P29 (reason code) Auto liability fee schedule adjustment
- P22 (reason code) Adjusted under auto PIP or MPC rules
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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