CO P23 denial code

Claim adjustment reason code P23. Often reported as CO P23.

Auto PIP or MPC fee schedule adjustment

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 P23 means

The auto insurer reduced the charge to the fee schedule amount that applies to personal injury protection or medical payments claims.

Auto carriers report it on medical claims under a car insurance policy. It is the auto version of a fee schedule reduction: the payer priced the service at the jurisdiction's PIP or medical payments fee schedule.

The remittance may identify the fee schedule used. Many states limit balance billing in these cases, so check before billing the patient.

Group codes seen with P23

On a remittance, P23 comes after a group code. These are the ones it is most often reported with:

• CO P23 (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 billed charge exceeds the state's auto fee schedule amount.
• The payer applied a fee schedule from another region or year.
• Fee schedule rules for multiple services reduced the allowance.

What to do next

1. Compare the payment with the applicable auto fee schedule.
2. Ask for reconsideration if the payer used the wrong schedule.
3. Post the difference as an adjustment if the payment matches the schedule.

Related codes

• P21 (reason code) Denied under auto PIP or MPC rules
• P22 (reason code) Adjusted under auto PIP or MPC rules
• P12 (reason code) Workers' comp fee schedule adjustment