CO-197 Denial Code: No Prior Authorization

The official definition

“Precertification/authorization/notification/pre-treatment absent”

That is the verbatim definition of CARC 197 from the X12 Claim Adjustment Reason Code set, the standardized codes every insurer uses on EOBs and remittance advices. The letters in front of the number are the group code. CO: Contractual Obligation: an adjustment between the provider and the insurer. An in-network provider should not bill you for CO amounts.

What it means in plain English

The insurer required pre-approval for this service and none was on file when the claim processed. In most cases, obtaining authorization was the provider's job. If they failed to do it, that's their problem, not yours. Emergency services are exempt from prior authorization entirely.

What to check on your EOB

• Whether this was emergency care. Prior authorization cannot be required for emergency services under federal law.
• Whether the provider's office told you authorization was needed, obtained, or pending before the service.
• The group code: CO on an authorization denial means the provider carries the contractual responsibility.

What to do next

1. Call the provider's billing office and ask directly: was prior authorization required, and did you obtain it?
2. If the provider failed to get authorization, tell them to pursue retroactive authorization or absorb the cost. Do not pay a bill caused by their failure.
3. If it was an emergency, contact the insurer and cite the prudent layperson standard and No Surprises Act emergency protections.
4. Check your state's rules. Many states prohibit billing patients when providers fail to obtain required authorization.

Who's responsible

Provider. Most denials carry a clear owner. Knowing whether the fix belongs to you, your doctor, or the billing office is half the battle. If it's the provider's error, you should not be paying for it.

Want the fundamentals first? Start with how to read an EOB and the 7 most common billing errors. This page is general information about standardized denial codes, not legal or medical advice.