CARC CO-29: Timely Filing Expired — DME Appeal Guide

CO-29 means the claim was submitted after the payer's allowed filing period expired. The official description: "The time limit for filing has expired." This is one of the few denials that can result in permanent write-off — once the window closes and no exception applies, the revenue is gone.

• Long setup-to-billing cycles. DME requires documentation from the ordering physician, CMN completion, delivery confirmation, and insurance verification before billing. When this chain takes too long, claims fall outside the filing window.
• Coordination of benefits delays. If you billed primary first and the COB process took 90+ days, the secondary filing window may have closed by the time you had the primary EOB.
• Staff turnover or claims sitting in queue. Denied claims that aren't worked promptly age past the appeal window. CO-29 on a re-billed claim is a billing management failure.
• Payer system errors. The payer's portal was down, the EDI gateway timed out, or a clearinghouse routing error caused a delay that wasn't the provider's fault.

1. Confirm you actually missed the deadline. Calculate exact days from DOS (or delivery date, per the payer's policy) to claim submission. If you're within the window, this is a payer error — appeal with EDI acceptance timestamps.
2. For Medicare: The timely filing limit is 12 months from DOS. If you're outside 12 months, the only path is a claim reopening under one of four CMS exceptions: (a) administrative error, (b) retroactive entitlement, (c) MAC system failure, or (d) other documented barrier outside your control.
3. For commercial payers: File an appeal with proof of timely submission (clearinghouse timestamp, EDI acceptance report, portal screenshot) or documentation of the exception (payer system outage, COB delay with primary EOB attached).
4. Write a tight appeal letter — state the denial reason, the filing deadline, your submission date, and the documented exception. One page. Attach every timestamp.
5. If there's no valid exception: Accept the write-off. Do not bill the patient for CO-29 denials — the contractual obligation write-off rule applies.