CO-29 Denial Code: Timely Filing Limit Expired

Every payer sets a time limit for submitting claims, measured from the date of service or from the primary payer's adjudication for secondary claims. Medicare's limit is 12 months from the date of service. Commercial and Medicaid limits vary by contract and state and can be as short as 90 days. CARC 29 means the payer has no record of a timely claim.

The group code (CO, PR, OA, PI) tells you who is responsible. The CARC number tells you why.

CO-29 means the payer received the claim after its filing deadline. You can only overturn it with proof that the claim was filed on time, such as a clearinghouse acceptance report. Without that proof it is usually a write-off, and in-network contracts typically bar billing the patient.

Common causes of CO-29.

• Clearinghouse or payer rejections that were never worked, so the claim never reached the payer
• Claims held for coding, documentation, or charge entry backlogs
• The wrong payer was billed first and the correct one was billed too late
• Secondary claims sent long after the primary paid
• Corrected claims submitted after the correction window

How to work a CO-29 denial.

The order matters: confirm the facts before deciding between a corrected claim, a reconsideration, or an adjustment.

1. 1Look for proof of timely filing: a clearinghouse acceptance report (999 and 277CA) showing payer acceptance, a prior denial from this payer, or a denial from another payer dated within the window.
2. 2If you have proof, submit a reconsideration or appeal with it attached.
3. 3If there is no proof, adjust the balance per your contract. Do not transfer it to the patient on in-network claims.
4. 4Trace why the claim was late and fix that step in the workflow.

How to keep CO-29 from coming back.

• Work clearinghouse rejections and payer acknowledgments daily
• Keep a timely filing table by payer and contract and flag claims approaching the limit
• Follow up on unpaid claims well before the deadline, not after

Fixing this at the source usually sits with ar follow-up specialists →

Questions about CO-29.

Denials that often travel with this one.

Browse all denial codes →

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