CO P26 denial code

Claim adjustment reason code P26. Often reported as CO P26.

Adjusted under a voluntary network (VPN)

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 P26 means

On a property and casualty claim, the payment was adjusted under a voluntary provider network (VPN) agreement.

Expect it from workers' compensation or auto medical carriers, since it is limited to property and casualty claims. A voluntary provider network is an arrangement providers choose to join to get access to property and casualty patients at negotiated rates. P26 means the payer applied that network's rate.

It is only used with group code CO. Check that you actually agreed to the network before accepting the reduction.

Group codes seen with P26

On a remittance, P26 comes after a group code. These are the ones it is most often reported with:

• CO P26 (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 provider joined a voluntary network that includes this carrier.
• The network applied a discount below the fee schedule.
• The carrier applied a network agreement you did not sign.

What to do next

1. Identify the voluntary network the carrier used.
2. Check your agreement with that network and its rates.
3. Dispute reductions that are not supported by a signed agreement.

Related codes

• P24 (reason code) Adjusted under a PPO arrangement
• P25 (reason code) Adjusted under a medical provider network