CO-2: Coinsurance Amount

What Does CO-2 Mean?

CO-2 shifts the coinsurance amount away from the patient and designates it as a contractual adjustment that the provider must absorb. This pairing is less common for CARC 2 but can occur when your participation agreement with the payer includes provisions that limit the coinsurance amount collectible from the patient, or when the payer incorrectly assigns the coinsurance to CO instead of PR.

When CARC 2 appears on a remittance, the payer is telling you that a percentage of the allowed amount has been assigned as the patient's coinsurance obligation. Unlike the deductible (CARC 1), which is a flat dollar threshold the patient must reach before coverage kicks in, coinsurance is a percentage split that applies after the deductible has been satisfied. The payer paid its contracted share of the allowed amount, and the remaining percentage belongs to the patient.

You will see CARC 2 most commonly paired with Group Code PR, confirming it as the patient's direct financial responsibility. The coinsurance percentage varies widely by plan — an 80/20 split is common, but high-deductible and out-of-network scenarios can push the patient's share to 30%, 40%, or higher. Out-of-network claims in particular tend to generate larger CARC 2 adjustments because the patient's plan applies a steeper coinsurance rate for non-participating providers.

While CARC 2 is generally not appealable since the payer adjudicated the claim correctly, you should always verify that the coinsurance percentage applied matches the patient's benefit plan. Errors in coinsurance calculation are not uncommon — the payer may apply the wrong plan tier, use an incorrect in-network vs. out-of-network split, or fail to credit prior payments that should have satisfied the coinsurance maximum. If the calculation is off, contact the payer for reprocessing rather than filing a formal appeal.

Common Causes

How to Resolve

Confirm the coinsurance calculation is accurate, then transfer the patient's coinsurance balance to their account and pursue collection.

1. Review your payer contract Check whether your participation agreement includes clauses that convert coinsurance to a contractual write-off for specific services or patient populations. If the CO designation matches your contract terms, the write-off is correct.
2. Verify the group code is correct CO-2 on a coinsurance adjustment is unusual. Contact the payer to confirm this was not a processing error where PR should have been assigned instead. If confirmed as PR, request a corrected remittance.
3. Post the contractual write-off If CO-2 is validated, write off the amount as a contractual allowance. Do not transfer this balance to the patient — your contract prohibits collection.
4. Flag for contract review If CO-2 coinsurance write-offs are recurring with this payer, document the financial impact and address it during contract renegotiation.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-2:

How to Prevent CO-2

• Maintain a summary of each payer contract's coinsurance collection rules so billing staff can anticipate which plans may generate CO-2 adjustments
• Audit remittances regularly to catch CO-2 assignments that should have been PR-2, since an incorrect group code directly reduces collectible revenue
• Negotiate contract terms that clearly define when coinsurance amounts are the patient's responsibility versus a contractual write-off

General Prevention

• Verify patient insurance eligibility and coinsurance percentage before every visit using real-time electronic eligibility verification tools
• Communicate coinsurance obligations to patients during scheduling and at check-in, including the estimated out-of-pocket cost based on the coinsurance rate
• Collect estimated coinsurance at the point of service using cost estimation tools that calculate the patient's share based on the allowed amount and plan coinsurance percentage
• Confirm whether the patient is using in-network or out-of-network benefits and explain the difference in coinsurance rates before rendering services
• Monitor remittances regularly to verify that coinsurance percentages are being applied correctly by payers and flag discrepancies for follow-up
• Train billing staff on coinsurance calculation methods, plan tier structures, and payer-specific coinsurance policies

Also Filed As

The same CARC 2 may appear with different Group Codes:

Related Denial Codes