CO-26: Expenses Incurred Prior to Coverage

What Does CO-26 Mean?

CO-26 indicates the payer is treating the denial as a contractual write-off — the service falls outside the coverage period and your contract does not obligate the payer to pay. Under CO, you cannot bill the patient for this amount directly based on the payer's adjudication. However, if you determine that no insurance covered the service and the denial is correct, you can reclassify the charges as patient self-pay (separate from the CO adjudication) and pursue collection. The first priority is to investigate whether the denial can be resolved through date correction, retroactive coverage, or an alternate carrier.

When CARC 26 appears on a remittance, the payer is telling you that the date of service on the claim falls before the patient's insurance coverage start date. The payer cannot reimburse for services that occurred during a period when the patient was not yet enrolled in their plan. This is a hard denial — no payment will be issued for the denied claim until the coverage gap is resolved.

The most common trigger is straightforward: the patient had not yet enrolled in the insurance plan when services were rendered. This frequently occurs with patients who are transitioning between jobs, aging onto Medicare, switching plans during open enrollment, or newly acquiring coverage through the marketplace. The patient may present an insurance card at registration without realizing the policy has not yet taken effect, or the enrollment processing may be delayed, pushing the official effective date past the service date.

However, not every CARC 26 is permanent. Some insurance programs — particularly Medicaid — offer retroactive coverage that can extend the effective date back to cover services rendered before the enrollment was processed. Additionally, the denial may stem from a simple data entry error where the date of service was recorded incorrectly. Before accepting the denial, providers should exhaust all avenues: verify whether retroactive coverage applies, confirm the date of service is accurate, and check whether the patient had other insurance in effect on the date of service.

Common Causes

How to Resolve

Verify the coverage effective date, check for retroactive eligibility or date errors, and either correct and resubmit or bill the patient if no coverage applies.

1. Verify coverage dates and service date accuracy Compare the coverage effective date against the claim's date of service. Check for data entry errors in either field.
2. Check for retroactive coverage or alternate insurance Contact the payer about retroactive eligibility. Ask the patient about other insurance that was active on the service date.
3. Correct and resubmit, or redirect to another carrier If a date error exists, correct and resubmit. If retroactive coverage is confirmed, request reprocessing. If another carrier was active, redirect the claim.
4. Bill the patient if no coverage existed If the service genuinely occurred before any coverage was active, communicate the situation to the patient and bill them directly.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-26:

How to Prevent CO-26

• Verify the coverage effective date — not just whether a policy exists — through real-time electronic eligibility verification before every visit
• For new patients or patients presenting new insurance cards, specifically confirm when coverage became effective before rendering services
• If coverage has not yet started, inform the patient they will be responsible for charges and collect payment at the time of service
• Submit claims promptly after service delivery to avoid confusion about coverage period applicability
• Flag patients whose insurance is recently activated and verify effective dates carefully during the first few visits

General Prevention

• Verify patient insurance eligibility including the coverage effective date before every visit, not just whether the policy exists but when it started
• Confirm the coverage effective date through real-time electronic eligibility verification, paying specific attention to the coverage start date field
• Ask new patients and patients presenting new insurance cards to confirm when their coverage became effective
• Submit claims promptly after service delivery to avoid confusion about which coverage period applies

Also Filed As

The same CARC 26 may appear with different Group Codes:

Related Denial Codes