CO-100: Payment Made to Patient/Insured

What Does CO-100 Mean?

CO-100 is less common and may appear when the payer's contract directs payment to the patient for specific situations — such as when the provider is out of network and the contract does not allow direct payment to non-participating providers. In this case, the payment routing is a contractual provision rather than an error.

CARC 100 appears on your remittance when the payer processed and paid the claim, but directed the payment to the patient, the insured individual, or the responsible party rather than to the provider. This is fundamentally different from a denial — the payer is not disputing the service, the coding, or the medical necessity. They are simply informing you that the check or EFT went to the patient's address instead of yours.

The most common trigger is a missing Assignment of Benefits (AOB) form. Without a signed AOB on file, the payer has no authorization to send payment to the provider and defaults to paying the patient. Out-of-network status is the second most frequent cause — many payers automatically direct payment to the patient when the rendering provider is not in their network, regardless of whether an AOB exists. Other causes include incorrect billing information (wrong NPI, tax ID, or pay-to address), coordination of benefits errors where the wrong entity receives payment, and terminated coverage situations.

From a workflow standpoint, CARC 100 creates a patient collection scenario rather than a payer dispute. The money is out the door and in the patient's hands. Your options are to collect from the patient, or to contact the payer and request reprocessing if you believe the payment was misdirected due to a payer error (such as an AOB being on file but ignored). Either way, prompt follow-up is essential because the longer the delay, the harder it becomes to recover funds from the patient.

How to Resolve

Determine why payment went to the patient, then either collect from the patient or request payer reprocessing if an AOB was on file.

1. Review the payer contract Check the provider's participation agreement with the payer to understand the payment routing rules, especially for out-of-network or non-participating scenarios.
2. Collect from the patient Contact the patient, explain that their insurance paid them directly for your services, and request payment of the amount owed.
3. Consider network participation If CO-100 is a recurring issue with a specific payer, evaluate whether joining the payer's network would resolve the payment routing problem.

How to Prevent CO-100

• Understand each payer's payment routing rules for participating and non-participating providers before rendering services
• Inform out-of-network patients that payment may be directed to them and obtain a payment agreement at the time of service
• Collect estimated amounts at the time of service for out-of-network patients to reduce collection risk

Also Filed As

The same CARC 100 may appear with different Group Codes:

Related Denial Codes