835 Denial Combination

CO-31

CO

Contractual Obligation · Claim-Level Adjustment

Eligibility

What This Combination Means

The payer has denied the claim because the patient's information does not match their enrollment records, indicating they cannot verify the patient as a covered member. Despite this being an eligibility issue, the CO group code requires the provider to write off the amount rather than bill the patient, which may indicate the provider was required to verify eligibility prior to service or submitted claims under a participation agreement that places eligibility verification responsibility on the provider.

Financial Responsibility

provider writeoff

The provider must write off the denied amount per contractual agreement with the payer, even though the denial stems from patient identification issues. The patient cannot be billed for this amount.

20%

Appeal Success

30-45 days (corrected claim or appeal with verification)

Avg. Resolution

Medium

Difficulty

Yes

Appealable

Step-by-Step Resolution

Steps tailored specifically to this CO-31 combination — not generic advice.

Appealable:If the patient was actually covered by the plan on the date of service but eligibility data was incorrect, a corrected claim with eligibility verification may recover payment.
  1. 1

    Obtain current insurance card and photo ID from patient

    The patient identification mismatch must be resolved by collecting accurate demographic and policy information directly from the patient to compare against what was originally submitted

  2. 2

    Compare submitted claim data against insurance card details for discrepancies in name, DOB, member ID, or subscriber information

    Common mismatches include misspelled names, transposed digits in member ID, incorrect date of birth, or wrong subscriber relationship

  3. 3

    Contact payer eligibility verification line or portal to confirm active coverage using corrected demographic information

    Real-time verification confirms the patient is enrolled and provides correct identifiers to use on the corrected claim

  4. 4

    File corrected claim with accurate patient identifiers or submit appeal with proof of eligibility if original data was correct

    Use Claim Change Reason Code (Claim Adjustment Reason Code for corrections) if demographic error was on provider side; use formal appeal process with eligibility printout if payer error is suspected

Specialty Context

How CO-31 typically presents across different practice types.

Dental

Common when dental offices collect outdated insurance cards or when patients have both medical and dental coverage under different member IDs with the same carrier

Medical

Frequently occurs with name changes due to marriage/divorce not updated in payer system, newborns not yet added to family policies, or when subscriber vs dependent information is reversed

Behavioral Health

May arise when behavioral health benefits are carved out to separate payer and patient provides medical plan information, or when patients have recently changed insurance but used old card

Individual Code References

View the standalone definition for each code in this combination.

CARC 31

Medicare Contractor Guidance for CARC 31

Noridian

Incorrect Medicare number was submitted on the claim. Beneficiary is not enrolled in Medicare.

How to Prevent CARC 31 Denials

  • ✓

    If the record on file is incorrect, the beneficiary's family/estate must contact the Social Security Administration to have records corrected.

Noridian Medicare Portal

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Synthesized from official definitions — not from training data

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