CO 155 denial code

Claim adjustment reason code 155. Often reported as CO 155.

Patient refused the service

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 155 means

The payer reports that the patient declined the service or procedure, so nothing is payable for it.

The claim or the payer's records show the patient refused the service. If the service was not given, it should not have been billed. If it was given, the claim data or the record is likely wrong.

This code usually traces back to a coding or charge entry problem. Check the record before doing anything else.

Group codes seen with 155

On a remittance, 155 comes after a group code. These are the ones it is most often reported with:

• CO 155 (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 charge was entered for a service the patient declined.
• The claim included a code or indicator showing the patient refused the service.
• Charges from an order were posted even though the service never took place.

What to do next

1. Check the record to confirm whether the service was given or refused.
2. Void or correct the claim if the service was not performed.
3. Fix charge capture so declined services are not billed in the future.

Related codes

• 115 (reason code) Procedure postponed, canceled or delayed
• 203 (reason code) Service discontinued or reduced