CO-29 Denials: Reconstruct the Filing Timeline Before You Write Off the Claim

A timely-filing denial can arrive months after the work that caused it: an unresolved rejection, a claim sent to the wrong payer, or a charge that never left the billing queue. Before closing the balance, reconstruct what happened from the date of service through payer receipt.

CARC 29 identifies an expired filing limit. The code alone does not establish which deadline applied, what the payer received, or whether an exception is available.

Build one filing timeline

Collect the date of service, charge-entry date, original submission date, clearinghouse responses, payer acknowledgment, claim number, and dates of any corrections. Include earlier remittances and payer correspondence.

An internal “submitted” status is incomplete evidence. Check the acknowledgment to determine whether the payer accepted the claim for processing, rejected it, or never received it. Keep those records together so the next person working the account can follow the sequence.

Check the rule for that payer and claim

Original Medicare generally requires claims to reach the correct Medicare Administrative Contractor within one calendar year after the service. CMS also states that an untimely-filing denial is not an initial determination and is not subject to the ordinary appeal process.

Commercial plans and other programs can have different filing limits, correction windows, and dispute procedures. Check the applicable contract and payer guidance. Record the rule, its source, and the deadline calculated for the account.

Use three review paths

1. The claim contains an incorrect date.

Compare the billed date with the clinical record. Noridian’s Part B guidance says to verify the date of service and submit a new claim with the corrected date when it was wrong. Change the date only to reflect when the service actually occurred. Document the correction and retain the original submission history.

2. Evidence shows a timely submission.

Identify the payer acknowledgment and claim reference that support the receipt date. Follow that payer’s process for reviewing an incorrectly applied filing denial. A clearinghouse transmission log may be useful, but establish what it proves about payer receipt before relying on it.

3. The claim was received late.

Check whether a defined exception applies. CMS describes exceptions involving qualifying administrative error, retroactive Medicare entitlement, certain Medicaid recoupments tied to retroactive entitlement, and qualifying retroactive disenrollment from Medicare Advantage or PACE. Each has conditions. Follow the contractor’s exception instructions and provide the relevant notices and dates.

Assign an owner to each path, with a dated next action. If the claim cannot be recovered, resolve the balance under the applicable payer rules and the practice’s adjustment process. Review patient liability before moving any amount to a patient account.

Prevent the next CO-29

Create a weekly list of claims approaching their filing deadline. Include encounters with unposted charges, rejected submissions, unresolved payer routing, and corrections awaiting action. Sort by days remaining and collectible balance.

For specialty practices, look at delays between the signed note, completed coding review, and first accepted submission. A chart hold can consume the filing window while the account still looks like routine work in progress.

Track days from service to submission, time spent in rejection queues, and CO-29 adjustments by cause. Use the review to fix the step that lost time and verify that the change reaches the next billing cycle.

Sources

X12: Claim Adjustment Reason Codes, CARC 29

https://x12.org/codes/claim-adjustment-reason-codes

CMS: Medicare Billing, Timely Filing and Exceptions for Late Filing

https://www.cms.gov/Outreach-and-Education/MLN/WBT/MLN4462429-MLN-WBT-1500/1500/lesson01/08/index.html

https://www.cms.gov/outreach-and-education/mln/wbt/mln4462429-mln-wbt-1500/1500/lesson01/09/index.html

Noridian: Timely Filing, JF Part B

https://med.noridianmedicare.com/web/jfb/topics/claim-submission/reason-code-guidance/timely-filing

How Syntra can help

Syntra reviews charts and claims before submission to identify coding and compliance issues. Practices can use a Syntra audit to examine encounters delayed by coding questions or documentation gaps, then establish review guidelines and targeted provider feedback. Bringing those issues into a consistent pre-bill workflow can help teams address chart-related holds while time remains to submit the claim.