OA-166: Payer's Plan Responsibility Ended

What Does OA-166 Mean?

OA-166 appears when the plan termination involves coordination with a successor plan or another payer. The OA group code signals that the responsibility for the claim is being transferred rather than simply denied. This typically occurs during employer plan transitions where the new payer should pick up claims for the transition period, or in situations where continuation coverage (COBRA) is in effect.

When CARC 166 appears on a remittance, the payer is telling you that it is no longer responsible for processing claims under the patient's plan. This does not necessarily mean the service was not covered at the time it was rendered — it means the payer's administrative responsibility for adjudicating claims under that particular plan has ended. The plan may have terminated, the employer may have switched insurance carriers, or the patient may have transitioned to different coverage.

This code frequently appears after plan year transitions, employer insurance changes, and during periods when patients move between coverage types (employer to marketplace, COBRA election or lapse, aging into Medicare). The denial may also trigger when claims are submitted well after the date of service and the plan has since been replaced. In some cases, retroactive plan terminations create a gap where the provider rendered services believing the patient was covered, but the plan was terminated effective a prior date.

The key distinction with CARC 166 is that it is not a judgment about medical necessity, coding accuracy, or coverage policy — it is purely an administrative determination that this specific payer is no longer the right entity to process the claim. Your path forward depends on the situation: if the patient has new coverage, submit to the new payer; if the plan terminated retroactively while the patient was still eligible, appeal to the original payer; if no coverage exists, bill the patient directly.

How to Resolve

Verify the patient's coverage dates, identify the correct payer, and either resubmit to the replacement plan or appeal if coverage was active at the time of service.

1. Identify the successor payer Contact the original payer or the employer to determine which new plan or payer has assumed claim processing responsibility.
2. Submit to the successor plan Redirect the claim to the successor payer with the patient's updated coverage information.
3. Request reprocessing if OA was applied incorrectly If the plan transition does not apply to this patient or date of service, contact the payer and request the claim be reprocessed.

How to Prevent OA-166

• Track plan transitions and successor payer information for major employer groups in your patient population
• Verify coverage during plan transition periods to ensure claims are routed to the correct payer
• Maintain contact with employer benefits administrators for timely notification of plan changes

Also Filed As

The same CARC 166 may appear with different Group Codes:

Related Denial Codes