Patient cannot be located to verify eligibility (Updated for 2026)

Common Causes for CO-31

Denials with code CO-31 typically happen for the following specific reasons:

• Outdated, incorrect, or incomplete patient demographic information (such as telephone number or physical address) recorded during patient intake.
• The payer is attempting to complete an annual coordination of benefits (COB) update, and the patient has failed to respond to the payer's inquiries.
• A mismatch between the patient's submitted name, date of birth, or member ID and the data on file in the payer's master member registry, preventing successful automated lookup.
• The patient has discontinued their policy or switched employers, and the payer cannot contact the subscriber to confirm the coverage end date.

How to Prevent CO-31 Denials

To avoid receiving this denial in the future, implement these specific checks:

• Utilize real-time eligibility (RTE) verification systems prior to or at the time of service to confirm active enrollment and identify any demographic discrepancies.
• Mandate front-desk staff to verify, update, and document patient contact information, including physical address and primary phone number, at every visit.
• Obtain a copy of both the front and back of the current insurance card during registration to verify the accurate payer contact details and member ID.
• Proactively counsel patients with potential Coordination of Benefits (COB) issues on the necessity of contacting their insurer directly to update their files.

Appeal Letter Template for CO-31

If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.

[Your Practice Header]
[Date]

[Payer Name]
[Appeals Department Address]

RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: CO-31 - Patient cannot be located to verify eligibility

Dear Appeals Department,

I am writing to appeal the denial of the above-referenced claim, which was denied with code CO-31: "Patient cannot be located to verify eligibility".

We are formally appealing the denial of this claim under code CO-31. On the Date of Service, our office verified active coverage for the patient, [Patient Name], under Member ID [Policy ID], as documented by the enclosed real-time eligibility response. We have attached the patient's verified demographic sheet, a copy of their insurance card, and proof of active coverage at the time of service. According to standard CMS and industry claims processing guidelines, when a provider confirms active eligibility at the time of registration and submits clean demographic data, the claim should be adjudicated accordingly. We request that you utilize the verified contact and demographic information enclosed to resolve the eligibility query and process this claim for payment.

Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].

We respectfully request that you reprocess this claim for payment.

Sincerely,

[Your Name]
[Title]
[Practice Name]