CO-15: Authorization number missing or invalid
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
Care that needed prior authorization was billed without a valid authorization number — sometimes because one was never obtained, sometimes because a valid number wasn't put on the claim.
CO-15 at a glance
- Code group: CO — Contractual Obligation — in-network providers generally cannot bill you for CO adjustments.
- Who usually fixes it: The provider’s billing office.
- Worth appealing? Sometimes — depends on the facts.
What to do about a CO-15 denial
- Ask the provider whether an authorization existed; if yes, they resubmit with the number.
- If authorization was never obtained, ask about a retroactive authorization request.
- If the payer refuses, appeal — especially where the service was urgent or the auth failure wasn't yours.
Best next read: Prior authorization denials — the full guide (with a free letter template) for this denial type.
Denied? Don’t drop it
Upload your denial letter. Get the whole appeal packet.
GetMyYes reads the actual letter — codes, fine print, deadlines — and drafts your appeal letter, evidence checklist, doctor letter request, and call script. Free preview first.
Start my appeal — free previewFREE PREVIEW · $39 FULL PACKET · NO SUBSCRIPTION. EVER.