CO 197 denial code

Claim adjustment reason code 197. Often reported as CO 197.

No prior authorization on file

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 197 means

The payer required precertification, authorization or notification for this service and has no record that it was obtained.

This is one of the most common front-end denials. The plan wanted approval or notice before the service, and when it checked its system it found nothing that matched this patient, service and date.

With group code CO the denial usually counts as provider liability, so the patient is normally not billed. A match can fail even when an auth exists, for example if the dates, units, codes or provider on the claim differ from what was approved.

Group codes seen with 197

On a remittance, 197 comes after a group code. These are the ones it is most often reported with:

• CO 197 (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

• No authorization was requested before the service was performed.
• An authorization exists but under a different provider, facility, CPT code or date range than the claim shows.
• The authorization number was left off the claim or entered in the wrong field.
• The service was urgent or added during the visit and no retro authorization was obtained.
• The patient's plan changed and the new plan has different authorization requirements.

What to do next

1. Search your records and the payer portal for an authorization covering this patient, code and date.
2. If an auth exists, correct the claim so the auth number, provider, codes and dates match it, then resubmit.
3. If none exists, check whether the payer accepts retro authorization requests for this situation.
4. Appeal with medical records when the service was emergent or the payer's auth list did not include it.
5. Review front-desk authorization checks for this service so the denial does not repeat.

Related codes

• 198 (reason code) Authorization limits exceeded
• 210 (reason code) Authorization not obtained in time
• 243 (reason code) Not authorized by network or PCP provider
• 204 (reason code) Not covered under the patient's plan