CO P13 denial code

Claim adjustment reason code P13. Often reported as CO P13.

Reduced under workers' comp 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 Nov 11, 2026.

What P13 means

The workers' compensation payer reduced or denied the line under a jurisdiction rule or payment policy not covered by another code.

Only workers' compensation payers use this code. P13 is a general jurisdictional code: the payer applied a state workers' compensation regulation or payment policy and could not find a more specific code to report it with.

A rule reference may come with it on the remittance, and that reference is the best guide to what happened.

Group codes seen with P13

On a remittance, P13 comes after a group code. These are the ones it is most often reported with:

• CO P13 (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

• A state billing rule, such as one on report requirements, was not met.
• The service is limited under the jurisdiction's payment policy.
• The claim lacked information the jurisdiction requires.

What to do next

1. Read the remark codes and any rule reference to identify the regulation applied.
2. Check the state's workers' compensation rules for that requirement.
3. Correct and resubmit or appeal through the state process as appropriate.

Related codes

• P12 (reason code) Workers' comp fee schedule adjustment
• P1 (reason code) State rule drove the adjustment
• P15 (reason code) Outside workers' comp treatment guidelines