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CO-155 Denial Code: Patient Refused the Service

CO-155 means the payer is not paying because the patient refused the service or procedure. If the service was actually performed, the claim or the payer's records are wrong and should be corrected or appealed.

Quick facts

Code
CO-155 (CARC 155)
Status
Active In use since June 30, 2003; last modified September 30, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider carries the adjusted amount. Because the patient declined, the payer treats the service as not billable to it.
  • PR (Patient Responsibility): The payer indicates the patient may be responsible, for example if the patient declined a covered alternative and chose something else. Check the plan and any signed patient agreement first.
  • OA (Other Adjustment): Informational use where neither party is assigned responsibility for the line.
Official description
Patient refused the service/procedure.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-155 means

CARC 155 reads simply “Patient refused the service/procedure.” It tells you the payer believes the patient declined the service billed, so there is no service to pay for. It is uncommon on professional claims and is usually a sign that something was billed that should not have been, or that the payer has conflicting information.

If the patient really did refuse, the charge should not have been on the claim. If the patient did not refuse, the payer needs corrected information.

Example: a vaccine is ordered and charged automatically at check-in, but the patient declines it in the exam room. The charge goes out anyway, and the payer, seeing the refusal in the records it requested, adjusts it as CO-155.

Common causes

  • Charges generated from orders rather than from documentation of what was performed.
  • Templates or protocols that auto-add services (screenings, immunizations, tests) the patient declined.
  • Refusal documented in the record that was sent to the payer for another reason.
  • Partially performed procedures billed as if completed, with notes that describe the patient stopping it.
  • Payer data error, where the refusal belonged to a different date or patient.

How to fix it

  1. Review the record for the date of service. Confirm whether the service was refused, partially performed, or fully performed.
  2. If refused, void the line or submit a corrected claim (resubmission code 7) removing it. Do not move the charge to the patient.
  3. If partially performed, submit a corrected claim with the discontinued-service modifier the payer requires and documentation of what was done.
  4. If fully performed, contact the payer to find the source of the refusal and file a reconsideration or appeal with the procedure note and any consent form.
  5. Write off any CO amount that remains after correction or appeal.

How to prevent it

  • Drop charges from documentation, not from orders, especially for injections, vaccines, and screenings.
  • Give staff a simple way to record refusals so the charge is removed at the same time.
  • Audit auto-added template services periodically for charges without matching documentation.
  • Scrub claims for services lacking a completed note before submission. More on avoidable errors in preventable claim denials.

Remark codes that may appear with CO-155

  • M127 (Missing patient medical record for this service.): The payer may need the medical record to confirm what was and was not done.
  • M111 (We do not pay for chiropractic manipulative treatment when the patient refuses to have an x-ray taken.): A specific refusal case: chiropractic manipulation is not paid when the patient refused a required x-ray.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): Denial for medical necessity, not because the patient refused.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): The service is not covered under the patient's benefit plan, which is a coverage issue rather than a refusal.
  • CO-96 (Non-covered charge(s).): A general non-covered charge denial.

CO-155 FAQ

Why would a claim be billed for a refused service?

Usually by mistake: a charge was loaded from an order or template, or the service was started and then stopped. Some payers also receive the refusal through records or a care-management report.

Can I bill the patient after CO-155?

Not under the CO group code. If the service was truly refused, there is usually nothing to bill anyone for it. Void the charge rather than transferring it to the patient.

What if the procedure was started but not finished?

That is not the same as a refusal. Bill the discontinued service with the appropriate reduced or discontinued modifier (such as 52, 53, 73, or 74, depending on setting and payer) and document why it stopped.