CO-197 denials: how to stop missing prior authorizations

A CO-197 denial means the payer expected a precertification, authorization or notification before the service and didn’t find one. The CO group code tells you the adjustment is a contractual obligation: in most cases you can’t bill the patient for it.

That makes CO-197 one of the most expensive denials a practice can receive. The visit happened, the work was done, and recovering payment depends on an appeal the payer has little reason to grant.

Why missing-authorization denials happen

In our experience, almost every CO-197 denial traces back to one of four gaps:

1. The requirement wasn’t checked at scheduling. Staff assumed a service didn’t need authorization because it didn’t last time, or for a different plan.
2. The patient’s coverage changed. A new plan year or a switch to a Medicare Advantage plan brought new authorization rules.
3. The service changed on the day. The provider added a procedure or imaging study that wasn’t on the original authorization.
4. The authorization expired or ran out of units. Therapy and infusion approvals often cover a fixed number of visits or a date range.

A related denial, CO-15, means an authorization exists but doesn’t match the claim: wrong provider, wrong dates, or the wrong number of units. The fix is the same: compare the claim with the approval before it goes out.

A scheduling checklist that prevents most CO-197 denials

Put the authorization check where the information is: at scheduling, not at check-in.

• Verify eligibility and the plan type when the appointment is booked, and again two business days before the visit.
• Check the payer’s current authorization list for the CPT or HCPCS codes you expect to bill. Payers update these lists several times a year.
• Submit with clinicals attached. Requests sent without the supporting notes are the ones that sit in pending.
• Record the approval number, approved codes, units and date range in your practice management system, where billing can see them.
• Flag same-day changes. If the provider adds a service during the visit, the front desk or billing team should check whether it needs its own authorization or a retro-authorization request.
• Track expirations for any authorization that covers a series of visits.

What to do when a CO-197 denial arrives

Not every CO-197 is final. Before writing it off:

• Check whether an authorization was actually obtained and simply not attached to the claim. If so, add it and submit a corrected claim.
• Ask whether the payer accepts retro-authorization for urgent or same-day services. Some do, within a short window.
• If the service was medically urgent, appeal with the clinical record and the payer’s own policy on emergency exceptions.

Faster payer decisions from 2026

Under the CMS Interoperability and Prior Authorization final rule, most Medicare Advantage, Medicaid and CHIP plans must decide standard requests within 7 calendar days and expedited requests within 72 hours from 2026. That shortens the wait, but it doesn’t remove the need to ask: a request that is never submitted still ends in a CO-197.

If missing authorizations are a regular line on your denial report, talk to us about prior authorization support. We check requirements at scheduling and track every request to a decision.