Undeny
PricingSign inBecome a founding pilot
CO-197Usually worth appealing

CO-197 denial: prior authorization absent

The payer says the service needed prior authorization and it did not have one on file when the claim was processed.

Official X12 description
Precertification/authorization/notification/pre-treatment absent.

What the CO group code means

CO — Contractual Obligation

The amount is written off under your contract with the payer. You cannot bill the patient for it.

Is it worth appealing?

CO-197 is one of the most appealable denial codes there is. A large share of these are administrative — the authorization existed, or was never actually required — and the payer simply did not match it to the claim.

Why payers issue CO-197

  • 01An authorization was obtained but the number never made it onto the claim.
  • 02The authorization was on file under a different rendering provider, facility, or date of service than the one billed.
  • 03The service was performed as an emergency or urgent case, where retroactive authorization rules apply instead.
  • 04The plan did not actually require authorization for this service, but the payer's edit fired anyway.
  • 05The authorization was requested and the payer failed to respond within its own decision window.
  • 06The units, site of service, or date range drifted from what was authorized.

What to gather before you appeal

  • The authorization or reference number, plus the date it was issued.
  • Any call reference number, fax confirmation, or portal screenshot showing the request was submitted.
  • The payer's own policy page or provider manual section listing what requires authorization.
  • The clinical documentation supporting that the service was performed as billed.
  • For urgent or emergent care, documentation of why pre-service authorization was not possible.

Arguments that work

  • Authorization existed — show the number and ask the payer to reprocess rather than re-adjudicate.
  • Authorization was not required under the member's plan — cite the payer's own published policy.
  • The payer missed its own decision deadline, so the service is deemed authorized under plan rules.
  • Retroactive authorization applies because the presentation was emergent and stabilization came first.

The deadline

Most commercial plans allow 90–180 days from the remittance date for a first-level appeal; Medicare Advantage plans commonly allow 60 days. The remittance advice states the governing window — always work from that, not from memory.

Common questions about CO-197

Is CO-197 worth appealing?
Usually, yes. CO-197 is an administrative denial far more often than a clinical one. If an authorization exists — or the service never required one — the appeal is largely a matter of putting the proof in front of the payer.
Can I bill the patient for a CO-197 denial?
No. CO is a Contractual Obligation group code, which means the amount is a write-off under your payer contract and cannot be balance-billed to the patient. That is exactly why appealing it matters — nobody else is going to pay it.
Did prior authorization rules change recently?
Yes. Under the CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F), impacted payers — Medicare Advantage, Medicaid and CHIP managed care, and QHPs on the federal exchanges — have been required since January 1, 2026 to decide standard prior authorization requests within 7 calendar days and expedited requests within 72 hours, and to give a specific reason for denials. A payer that blew its own decision window is a strong appeal argument.
What if we never requested authorization at all?
The appeal is narrower but not hopeless. The two live arguments are that the plan did not require authorization for this service, or that the clinical situation was emergent and retroactive authorization rules apply. Check the payer's published policy before writing.

Draft the CO-197 appeal in about three minutes

Upload the denial. Undeny reads it, drafts a payer-specific appeal letter citing this code and the record, and tracks the deadline until the money comes back.

Generate your appeal letterSee pricing

Other denial codes