How do I resolve a CO-27 denial?

Verify the patient's actual coverage termination date: Request eligibility transaction history or coverage documentation to confirm the exact date coverage ended versus the date of service Compare date of service against confirmed eligibility status: If services were rendered while coverage was active or during a grace period, gather proof of active coverage at time of service including eligibility verification responses Submit appeal with eligibility documentation if dates conflict: Include timestamped eligibility verification showing active coverage at time of service, or documentation of retroactive coverage reinstatement that covers the service date Write off the balance if termination date is confirmed accurate: If the patient was definitively not covered on the date of service and no eligibility error exists, apply contractual write-off and do not bill patient

835 Denial Combination

CO-27

Contractual Obligation · Claim-Level Adjustment

Eligibility

What This Combination Means

The payer has denied this claim because services were rendered after the patient's insurance coverage ended. Under contractual obligation, the provider must write off the denied amount and cannot balance bill the patient for these charges, even though the patient was not eligible at the time of service.

Financial Responsibility

provider writeoff

The provider is contractually required to write off the full amount. The patient cannot be billed for services rendered after their coverage termination date.

15%

Appeal Success

30-60 days (eligibility verification and potential appeal)

Avg. Resolution

Hard

Difficulty

Yes

Appealable

Step-by-Step Resolution

Steps tailored specifically to this CO-27 combination — not generic advice.

Appealable:Eligibility-based denials may be recoverable if the patient was actually eligible and eligibility data was incorrect, or if the service falls under a secondary coverage. Verify eligibility and consider rebilling.

1
Verify the patient's actual coverage termination date
Request eligibility transaction history or coverage documentation to confirm the exact date coverage ended versus the date of service
2
Compare date of service against confirmed eligibility status
If services were rendered while coverage was active or during a grace period, gather proof of active coverage at time of service including eligibility verification responses
3
Submit appeal with eligibility documentation if dates conflict
Include timestamped eligibility verification showing active coverage at time of service, or documentation of retroactive coverage reinstatement that covers the service date
4
Write off the balance if termination date is confirmed accurate
If the patient was definitively not covered on the date of service and no eligibility error exists, apply contractual write-off and do not bill patient

Specialty Context

How CO-27 typically presents across different practice types.

Dental

Commonly occurs when patients lose employer-sponsored dental coverage mid-treatment or when COBRA/continuation coverage lapses during active orthodontic or multi-visit treatment plans.

Medical

Frequent with job changes, Medicare/Medicaid disenrollment, or when services span a coverage termination date such as inpatient stays, ongoing therapy, or chronic care management.

Behavioral Health

Often seen in ongoing therapy or substance abuse treatment when coverage ends mid-treatment episode, or when Medicaid eligibility lapses due to redetermination or income changes.

Individual Code References

View the standalone definition for each code in this combination.

CARC 27

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Synthesized from official definitions — not from training data

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