CO-29 Denial Code: Timely Filing Limit Expired

What CO-29 means

CARC 29 says the time limit for filing has expired. Every payer sets a deadline for submitting claims, usually counted from the date of service (or discharge date for inpatient stays). If the payer receives the claim after that deadline, it denies with CO-29 regardless of whether the care was covered and necessary.

Because the group code is CO, the loss belongs to the provider. Unless you can prove the claim was filed in time, or an exception applies, the amount is typically written off. That makes CO-29 one of the most costly preventable denials: the service was delivered, documented, and often covered, but the revenue is gone.

For a full breakdown, see our deep dive on CO-29 timely filing denials.

Common causes

• Claims stuck in the system. Charges held for missing information, unsigned notes, or coding questions until the deadline passes.
• Front-end rejections not worked. A clearinghouse or payer rejects the claim, no one fixes it, and by the time it’s resubmitted the limit has passed. See claim rejection vs. denial.
• Wrong payer first. The claim went to the wrong insurer, and by the time the correct one was identified, its deadline had expired.
• Secondary claims filed late while waiting on the primary.
• Corrected claims past the limit. Some payers apply the original deadline to corrected claims as well.
• Short commercial or Medicaid limits that differ from what staff assume.
• Credentialing delays, where claims are held until a provider is enrolled.

How to fix it

1. Check the dates. Confirm the date of service and the date the payer first received the claim. Make sure the denial isn’t based on a wrong service date.
2. Gather proof of timely filing. Clearinghouse acceptance reports showing payer receipt, 277CA acknowledgments, payer portal submission records, earlier ERAs, or denial letters for the same claim.
3. Appeal or request reconsideration with that proof, following the payer’s process and its appeal deadline.
4. Look for an exception. Retroactive eligibility, payer error, or a delayed primary payment can support an exception under some payer policies. Include documentation.
5. If there’s no proof and no exception, write off the amount as a timely filing adjustment. Do not bill the patient.
6. Record the root cause so the same gap doesn’t repeat.

How to prevent it

• Keep a timely filing table for every payer you bill, including limits for original claims, corrected claims, secondary claims, and appeals.
• Submit claims promptly, ideally within days of the service.
• Work rejections daily. A rejection is a clock that keeps running.
• Save proof of submission for every claim, including clearinghouse acceptance and payer acknowledgments.
• Run aging reports by payer deadline, not just by days outstanding, so claims near their limit get priority.
• Scrub before submission. A Claims Validator reduces rejections that eat into filing time.
• Verify coverage up front so claims go to the right payer first. See eligibility and COB denials.

Specialty notes

Behavioral health and therapy practices with high visit volumes can lose many small claims to timely filing when a payer setup problem goes unnoticed for months. Workers’ compensation and auto claims have their own filing rules under state law, which differ from group health limits.