Denial playbooks

Timely Filing Denials (CARC 29): The Recovery Playbook for Dental Claims

Revamend team · July 2, 2026 · 7 min read

Claim Adjustment Reason Code 29, printed as CO-29, means "the time limit for filing has expired." The payer is saying your claim arrived after its filing deadline, and the CO group code makes the balance a provider write-off that cannot be billed to the patient. It feels final. It frequently is not. Timely filing denials are overturned more often than almost any other administrative denial, because the payer's only question is whether you can prove the claim was filed on time or had a valid reason to be late. Often you can.

Typical filing windows by payer type

Filing limits run from the date of service unless the contract says otherwise. Always confirm the limit in your specific participation agreement, but these ranges are typical:

• Commercial dental PPOs: commonly 90 days to 12 months, with 6 or 12 months most frequent. In-network contracts often impose shorter limits than the plan's out-of-network rule.
• Medicaid dental programs and their managed care plans: often 90 to 180 days, and some states are stricter. Managed care organizations can set their own limits within state rules.
• Medicare Advantage plans with dental benefits: typically 12 months, but plan contracts vary.
• Secondary claims: the clock usually runs from the primary payer's EOB date, not the date of service, though contracts differ. This distinction wins many appeals on its own.

The proof-of-timely-filing appeal

The strongest CO-29 appeal is not an argument, it is a receipt. Payers deny for timely filing based on the date they show the claim in their system. If you can document an earlier submission, the denial should be reversed. Evidence, in rough order of strength:

• Clearinghouse acceptance reports. The 999 or 277CA acknowledgment showing the payer accepted the claim on a specific date is the gold standard. Pull the acceptance report for the original submission, highlight the claim, and attach it.
• Clearinghouse submission logs. Even without a payer acknowledgment, a dated log showing the claim left your clearinghouse for that payer supports the appeal.
• Practice management system records. Batch submission reports and claim status history from your PMS showing the original submission date.
• Payer correspondence. Any earlier rejection, development request, or EOB referencing the same claim proves the payer had it inside the window.

Write a short cover letter: the claim was originally submitted on this date, within the filing limit, evidence attached, please reprocess. Send it through the payer's designated appeal channel and keep proof of the appeal submission too.

Exceptions that excuse late filing

Even when the claim genuinely was filed late, most payers recognize exceptions. Cite the specific circumstance and document it:

• Coordination of benefits delays. You could not bill the secondary until the primary paid. Attach the primary EOB showing its date and note that the secondary claim followed promptly.
• Retroactive eligibility. The patient's coverage was granted or discovered after the date of service, common with Medicaid determinations and employer coverage corrections. The window should run from the date eligibility was established or discoverable.
• Payer-caused errors. The payer gave you wrong eligibility information, misdirected the claim, lost a correctly filed claim, or had a portal or EDI outage. Reference call dates, reference numbers, and any payer notices.
• Incorrect insurance information from the patient. Many contracts allow an exception when the practice billed the wrong carrier in good faith and refiled promptly after learning the correct one. Attach the first carrier's rejection or denial as proof of the timeline.

When to write it off

Some CO-29 denials are legitimate: the claim sat unbilled past the deadline with no exception available and no proof of earlier submission. Appealing those wastes staff time and dilutes your credibility with the payer. Write them off, but record the root cause. A pattern of legitimate timely filing write-offs is an operations problem with a calculable monthly cost, and it is usually cheap to fix.

Prevention through claim tracking

• Submit claims daily, not weekly. Batching is the quiet killer of filing windows.
• Work clearinghouse rejections within 48 hours. A rejected claim has not been filed for timely filing purposes with most payers.
• Run an unbilled procedures report weekly and an outstanding claims aging report at 30 days, well inside even the shortest windows.
• Keep a payer filing limit reference sheet from your actual contracts, and flag the short-window payers in your PMS.
• Archive clearinghouse acceptance reports where you can retrieve them by claim, since they are your appeal evidence.