Denial code CO-29: Timely filing limit exceeded
The claim reached the payer after its filing deadline, so it will not be adjudicated — and in most contracts the balance cannot be billed to the patient.
The time limit for filing has expired.
What CO-29 actually means
This is the most expensive denial in the book, because it is pure lost revenue on a service that was actually rendered: the payer never evaluated medical necessity or coverage, it simply refused to look. Filing windows range from 90 days to a year or more depending on the contract, and most provider agreements bar billing the patient for a claim lost to the provider’s own filing delay. CO-29 is worth appealing only where you can prove timely submission or a qualifying exception — and worth systematically preventing everywhere else.
Why this denial happens
- The claim sat unbilled in a work queue, a hold, or a charge-entry backlog.
- The claim was filed on time to the wrong payer and re-routed after the window closed.
- A denied claim was reworked slowly and resubmitted past the deadline.
- A clearinghouse rejection was never worked, so the payer never received the claim at all.
How to resolve a CO-29 denial
- Look for proof of timely submission — a clearinghouse acceptance report or payer acknowledgement is the strongest evidence available.
- Appeal with that proof attached where the original submission was in fact timely.
- Where another payer’s adjudication delayed filing, cite the primary’s remittance date, which many contracts recognise as an exception.
- Check the provider agreement before billing the patient — most contracts prohibit it for provider-caused filing delays.
How to prevent it
- Track days-since-date-of-service on every unbilled and denied claim and escalate well before the deadline.
- Work clearinghouse rejections daily — a rejected claim was never received and the clock keeps running.
- Record each payer’s filing window and drive a worklist from the earliest deadline first.
Frequently asked
What does denial code CO-29 mean?
The claim reached the payer after its filing deadline, so it will not be adjudicated — and in most contracts the balance cannot be billed to the patient. The X12 description reads: "The time limit for filing has expired."
How do I fix a CO-29 denial?
Look for proof of timely submission — a clearinghouse acceptance report or payer acknowledgement is the strongest evidence available. Appeal with that proof attached where the original submission was in fact timely. Where another payer’s adjudication delayed filing, cite the primary’s remittance date, which many contracts recognise as an exception. Check the provider agreement before billing the patient — most contracts prohibit it for provider-caused filing delays.
Can CO-29 be billed to the patient?
Generally no. The recommended path for this code is "appeal or correct and resubmit" — check your payer agreement before transferring any balance to the patient.
Related denial codes
Related billing terms
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General revenue-cycle guidance, not legal, coding, or payer-specific advice. Claim adjustment reason codes are maintained by X12 and are revised periodically; payer policy and your provider agreement govern in any specific case. Always read the remark codes transmitted with the denial — they frequently carry the detail this code does not.