CO 29: Timely Filing Limit Expired
Filed after the payer deadline.
Not appealable on Original Medicare, so do not file a redetermination there. If you can prove the Medicare contractor received the claim in time, or one of the four exceptions in 42 CFR 424.44(b) applies, send that proof to the contractor and ask it to review the denial, through the process it publishes. A commercial or Medicare Advantage payer is different: appeal or ask for reconsideration under its own process, with proof of timely filing.
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What CO 29 means
CO: Contractual obligation. The provider absorbs it and cannot bill the patient.
So the balance cannot move to the patient. Either the appeal recovers it or the practice absorbs it. That makes the appeal decision the whole decision on this line.
Is It Worth Appealing?
Usually lost. Recoverable only with unusual evidence. Triage by dollar value.
Why It Fires
In the order we see it.
The claim was filed after the payer's deadline.
An Original Medicare claim reached the Medicare contractor more than 1 calendar year after the date of service. A submission that was rejected or returned as incomplete does not count as filed.
The primary paid late and the secondary clock ran out.
The claim rejected at the clearinghouse and was never resubmitted.
How to Appeal CO 29, Step by Step
Not appealable on Original Medicare, so do not file a redetermination there. If you can prove the Medicare contractor received the claim in time, or one of the four exceptions in 42 CFR 424.44(b) applies, send that proof to the contractor and ask it to review the denial, through the process it publishes. A commercial or Medicare Advantage payer is different: appeal or ask for reconsideration under its own process, with proof of timely filing.
- 1Step 1: Read the remark code. Find the remark code printed next to CO 29 on the 835 or EOB. It says what the payer wants back.
- 2Step 2: Find the cause. Match the denial to one of the 4 causes in Why It Fires above, and fix that one.
- 3Step 3: Take the first action. Not appealable on Original Medicare, so do not file a redetermination there. If you can prove the Medicare contractor received the claim in time, or one of the four exceptions in 42 CFR 424.44(b) applies, send that proof to the contractor and ask it to review the denial, through the process it publishes. A commercial or Medicare Advantage payer is different: appeal or ask for reconsideration under its own process, with proof of timely filing.
- 4Step 4: Attach the documentation. The payer's own receipt date for the first submission, from its claim acknowledgement or claim status. For Original Medicare this is the date that counts: the date the Medicare contractor received the claim. For a commercial or Medicare Advantage payer, a clearinghouse acceptance report carrying the original submission date. The primary payer's EOB date, where the delay was theirs. For an Original Medicare exception, the documents 42 CFR 424.44(b) calls for, for example the notice of retroactive entitlement or the written notice of the contractor's own error.
- 5Step 5: Send the appeal before the deadline. Send it to the payer with the claim, the denial and the documentation, inside the payer's appeal window. See what an appeal letter must contain and the filing limits by payer.
Medicare claims. Medicare sets one limit for every Part A and Part B claim, 12 months from the date of service, and a late claim cannot be appealed. See the Medicare timely filing limit for how the dates are counted and the four exceptions. Medicare Advantage plans and commercial payers set their own limits: check your contract.
The common mistake. Do not send an Original Medicare timely filing denial to redetermination. The denial carries no appeal rights, so the request only uses up time. With any payer, do not argue without a date stamp: without proof the claim arrived in time there is nothing to argue.
Free: the Denial Code Appeal Playbook. 53 codes on one sheet: appeal, fix and resubmit, or let it go, and what to attach. Get the playbook
CO 29 description
Filed after the payer deadline.
Filed after the payer deadline. So the balance cannot move to the patient. Either the appeal recovers it or the practice absorbs it. That makes the appeal decision the whole decision on this line.
This is our plain-English wording, not the official X12 text. X12 asserts copyright over the published descriptions, so we write our own and say what it means for the money rather than restating the code.
Where this comes from. This is our own reading of the code, not the payer's and not a copy of the standards text. We classify it from how these denials actually resolve. Where we are unsure, we say so rather than guessing.
Your Questions Answered
What does CO 29 mean?
Filed after the payer deadline. Contractual obligation. The provider absorbs it and cannot bill the patient.
Can you appeal CO 29?
Usually lost. Not appealable on Original Medicare, so do not file a redetermination there. If you can prove the Medicare contractor received the claim in time, or one of the four exceptions in 42 CFR 424.44(b) applies, send that proof to the contractor and ask it to review the denial, through the process it publishes. A commercial or Medicare Advantage payer is different: appeal or ask for reconsideration under its own process, with proof of timely filing.
Why does CO 29 happen?
The claim was filed after the payer's deadline. An Original Medicare claim reached the Medicare contractor more than 1 calendar year after the date of service. A submission that was rejected or returned as incomplete does not count as filed. The primary paid late and the secondary clock ran out. The claim rejected at the clearinghouse and was never resubmitted.
What documentation wins a CO 29 appeal?
The payer's own receipt date for the first submission, from its claim acknowledgement or claim status. For Original Medicare this is the date that counts: the date the Medicare contractor received the claim. For a commercial or Medicare Advantage payer, a clearinghouse acceptance report carrying the original submission date. The primary payer's EOB date, where the delay was theirs. For an Original Medicare exception, the documents 42 CFR 424.44(b) calls for, for example the notice of retroactive entitlement or the written notice of the contractor's own error.
How do I appeal a CO 29 denial?
Step 1: Read the remark code. Find the remark code printed next to CO 29 on the 835 or EOB. It says what the payer wants back. Step 2: Find the cause. Match the denial to one cause: The claim was filed after the payer's deadline. An Original Medicare claim reached the Medicare contractor more than 1 calendar year after the date of service. A submission that was rejected or returned as incomplete does not count as filed. The primary paid late and the secondary clock ran out. The claim rejected at the clearinghouse and was never resubmitted. Step 3: Take the first action. Not appealable on Original Medicare, so do not file a redetermination there. If you can prove the Medicare contractor received the claim in time, or one of the four exceptions in 42 CFR 424.44(b) applies, send that proof to the contractor and ask it to review the denial, through the process it publishes. A commercial or Medicare Advantage payer is different: appeal or ask for reconsideration under its own process, with proof of timely filing. Step 4: Attach the documentation. The payer's own receipt date for the first submission, from its claim acknowledgement or claim status. For Original Medicare this is the date that counts: the date the Medicare contractor received the claim. For a commercial or Medicare Advantage payer, a clearinghouse acceptance report carrying the original submission date. The primary payer's EOB date, where the delay was theirs. For an Original Medicare exception, the documents 42 CFR 424.44(b) calls for, for example the notice of retroactive entitlement or the written notice of the contractor's own error. Step 5: Send the appeal before the deadline. Send it to the payer with the claim, the denial and the documentation, inside the payer's appeal window.
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