Common causes of code 109 are:

1. Incorrect payer or contractor information: One of the most common causes of code 109 is submitting the claim or service to the wrong payer or contractor. This can happen due to errors in the patient's insurance information or confusion about the correct payer for a specific service.

2. Out-of-network services: Code 109 may be triggered when a claim or service is not covered by the patient's insurance plan because the provider is considered out-of-network. This can occur when a patient seeks care from a provider who is not contracted with their insurance company.

3. Lack of pre-authorization: Some insurance plans require pre-authorization for certain services or procedures. If a provider fails to obtain the necessary pre-authorization before providing the service, the claim may be denied with code 109.

4. Non-covered services: Code 109 can also be caused by submitting a claim for a service that is not covered by the patient's insurance plan. This can include experimental or investigational treatments, cosmetic procedures, or services that are deemed medically unnecessary.

5. Incorrect coding: Incorrect coding can lead to claim denials with code 109. If the provider uses incorrect procedure codes or diagnosis codes that are not covered by the payer, the claim may be denied.

6. Termination of coverage: Code 109 may be triggered if the patient's insurance coverage has been terminated or if the policy has expired. This can happen if the patient fails to pay their premiums or if their coverage is terminated for other reasons.

7. Coordination of benefits issues: Code 109 can also be caused by coordination of benefits (COB) issues. This occurs when a patient has multiple insurance plans, and there is confusion about which plan should be billed first.

It is important for healthcare providers to address these common causes of code 109 to ensure accurate and timely reimbursement for their services.