CO-27 denial code
Expenses incurred after coverage terminated
How to fix it
Verify the actual termination date. If the patient has new coverage, bill that payer; if not, the balance transfers to patient responsibility.
How to prevent it
Verify eligibility before every visit rather than at intake only. Coverage terminations are invisible until you check.
In practice
A patient attends for a follow-up visit. The claim returns CO-27 — expenses incurred after coverage terminated. Their employment ended six weeks earlier and the plan terminated at the end of that month.
Eligibility had been verified, at the patient's first visit eight months previously. Nothing since. The patient did not mention the change, and from the practice's perspective nothing looked different.
The balance transfers to the patient unless they have new coverage, and a patient who has just lost their job receiving an unexpected bill is both a collection problem and a difficult conversation that a thirty-second eligibility check would have prevented.
What sits behind it
Coverage termination is invisible without checking. There is no notification to the practice, the insurance card remains in the patient's wallet and looks identical, and the patient frequently does not connect their employment change to their medical billing.
Registration and eligibility errors are the single largest denial category industry-wide, at 21.9% in Optum's analysis of 124 million claim remits. Termination is a substantial share of that, and it is among the most mechanically preventable denials in existence.
The control is verifying eligibility before every visit rather than at intake. Electronic verification takes seconds, returns the payer's own record rather than the patient's recollection, and catches terminations, plan changes and coverage that was never active in the first place.
Related codes
Terms used here — Eligibility Verification · Patient Responsibility · Denial
How we handle it — Eligibility Verification · Patient Collections · Denial Management
Primary sources
The rules behind CO-27, at the bodies that publish them.
- Medicare Secondary Payer Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — When Medicare pays second, and to whom the claim goes first. Coordination-of-benefits denials are resolved here rather than with the patient.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Claim Adjustment Reason Codes (CARC) (opens in a new tab)
X12 — The authoritative, maintained CARC list. Our denial code lookup explains these in plain English; X12 is where the canonical definitions live.
Every denial code with a guide
Authorization
Bundling
Contractual
Coverage
Data quality
Documentation
Eligibility
Liability and workers comp
Patient responsibility
Provider eligibility
Timely filing
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-27
Generally yes, since there is no coverage to absorb it. Check first whether the patient obtained new coverage responsible for the date of service, and whether any continuation coverage applies retroactively.
Because termination is invisible without checking. No notification reaches the practice, the insurance card looks identical, and patients frequently do not connect an employment change to their medical billing. Only verification against the payer's record surfaces it.
Verify eligibility before every visit rather than at intake only. Electronic verification takes seconds and returns the payer's current record. Registration and eligibility errors are the largest denial category industry-wide at 21.9%, and termination is a substantial share of it.
Some coverage, including continuation coverage and certain Medicaid determinations, is granted retroactively. Where that applies, rebill the correct payer — but watch the filing deadline, which usually runs from the date of service rather than the coverage determination.
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