CO-27: Expenses incurred after coverage ended
UPDATED · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
The payer believes your policy had already terminated on the date of service. Frequently an eligibility-file error after job changes or plan renewals.
CO-27 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-27 denial
- Verify your termination date with HR, the marketplace, or the insurer's eligibility department.
- If coverage was active (including COBRA), send proof and request reprocessing.
- Appeal with the paper trail if the payer won't correct the date.
Best next read: Free appeal letter template — the full guide (with a free letter template) for this denial type.
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