CO 197 denial code

What CO-197 means

CO-197 means the payer required precertification, prior authorization, or advance notification for the service, and its system found none on file. Either nobody obtained the approval, or the approval exists but the claim does not reference it correctly.

The CO group code is the painful part. Contractual obligation means the write-off is yours; the patient cannot be billed for a missed authorization. This is why CO-197 is one of the most expensive preventable denials; the service was likely covered, and the revenue is lost to a process failure.

Common causes

• No one requested authorization before the service was scheduled or performed.
• Authorization was obtained but the number was left off the claim: on paper it belongs in CMS-1500 Item 23; electronically, in the prior authorization reference of the 837 claim.
• The authorization covers a different CPT code, date range, provider NPI, or facility than what was billed.
• The payer changed its authorization list and a service that never needed approval now does.
• A Medicare-required prior authorization (certain hospital OPD services, some DMEPOS items) was non-affirmed or the unique tracking number (UTN) was omitted from the claim.

How to fix and resubmit

1. Check whether an authorization actually exists. Search the payer portal and your PM system by patient, date, and code.
2. If it exists, compare every element (CPT code, dates, rendering NPI, facility) against the claim. Fix the mismatch or add the number to CMS-1500 Item 23 (or the 837 equivalent) and submit a corrected claim.
3. If no authorization exists, check the payer’s policy for retroactive authorization. Many plans allow it within a defined window, especially for urgent or emergent care or eligibility discovered late. Submit the retro request with clinical notes, then resubmit the claim once approved.
4. If retro authorization is refused, appeal. Strongest arguments: the service was emergent, the payer’s own tool said no authorization was required (keep screenshots), or the patient’s coverage could not have been verified in time. Attach documentation for whichever applies.
5. If the appeal fails and no exception applies, write off the CO amount. Track it. A pattern of CO-197 write-offs is a scheduling-workflow problem, not a billing problem.

How to prevent it

Make authorization a hard stop in scheduling: no authorization-required service gets booked without an approval number and its date range recorded. Verify the requirement per payer at booking; check the payer’s policy rather than relying on last year’s list, because payers add and remove codes constantly. Confirm the authorization still matches if the procedure, provider, or date changes after booking. For Medicare OPD and DMEPOS prior-auth programs, append the UTN to every claim. Reconcile weekly: every authorization obtained should match a claim that carried it.

Related: CO-198 covers the neighboring failure (an authorization that exists but was exceeded). See the denial codes index for the full series.