CO-243: Services not authorized by network/primary care providers
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
Your plan (often an HMO) required a referral or PCP authorization that isn't on file.
CO-243 at a glance
- Code group: CO — Contractual Obligation — in-network providers generally cannot bill you for CO adjustments.
- Who usually fixes it: You and the billing office together.
- Worth appealing? Sometimes — depends on the facts.
What to do about a CO-243 denial
- Ask your PCP's office whether a referral was issued; if yes, have it resubmitted with the claim.
- If no referral was issued, ask about a retroactive referral — offices handle these routinely.
- Appeal when the care was urgent or a referral genuinely existed.
Best next read: Prior authorization denials — the full guide (with a free letter template) for this denial type.
Denied? Don’t drop it
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