CO-31: Payer cannot match patient to coverage

The payer is saying they do not see this person as insured under the information on the claim. The member ID, name, date of birth, relationship, or plan on the claim does not line up with what their system has for any active member. Mechanically, the claim fails eligibility edits before pricing. The payer compares the claim fields to their enrollment file and cannot find a valid match, so they assign CO-31 and pay zero. Because it is a CO adjustment, the payer expects the balance to be written off unless you correct the data and resubmit as a new or corrected claim.

In behavioral health, CO-31 often shows when eligibility was verified once at admission, then the member quietly changed plans during a long stay. A residential or PHP claim that spans a month boundary can deny if the client moved between Medicaid MCOs or into a carve-out, and you billed the wrong plan for some or all dates. It is also common with IOP and PHP per-diem billing on UB-04 when front desk staff used an old member ID from a prior employer plan, but the client is actually on an exchange plan or Medicaid now. The authorization may sit with the correct behavioral-health carve-out, but claims accidentally go to the medical payer that no longer shows the patient as covered. For OTP and MAT services billed weekly, CO-31 shows up when the Medicaid ID is mistyped or when the state moves the member into a different MCO mid-month and the clinic keeps submitting under the old payer. You lose the entire week of bundled payments until the ID and payer are corrected and re-billed.

• Check the payer's eligibility portal or IVR for the exact member ID, name format, date of birth, and plan for the dates of service.
• Confirm you billed the correct payer and product line, especially for Medicaid MCOs and behavioral-health carve-outs active on those dates.
• Compare the eligibility data to the claim: correct any member ID typos, name sequence issues, missing middle initials if required, or wrong subscriber vs dependent selection.
• If the payer changed mid-stay, split the claim by date range and submit each portion to the correct active plan with matching authorization if required.
• Rebill clean claims to the correct payer or resubmit as a corrected claim following payer rules, including any required frequency code or resubmission reference.
• If eligibility truly did not exist for the dates, document the finding, update the account to patient-responsibility or charity policy as appropriate, and close out the balance.

• Run and document real-time eligibility for all behavioral levels of care at admit and again at each month rollover for long stays.
• Train intake staff to capture the exact member ID from the current card and to verify payer, product, and behavioral-health carve-out details.
• Configure your billing system and clearinghouse edits to flag missing or format-incorrect member IDs, subscriber relationships, and primary payer mismatches before submission.
• When a payer change is detected mid-episode, update the patient registration and authorization records immediately and route future claims to the new payer.