Denial codes · Denial code
CO-29 timely filing denial: what still works and what doesn't
By Javier Alvarez · Updated · 4 min read
| Official description | The time limit for filing has expired. |
|---|---|
| Group code | CO: in network, not billable to the patient |
| Medicare Part B limit | 1 calendar year after the date of service (42 CFR 424.44) |
| Commercial limits | Set by contract; often 90 to 180 days, some up to a year |
| What wins an appeal | An accepted acknowledgment dated within the window |
| What doesn't | A rejected submission, or 'we sent it' |
CO-29 is the denial with the fewest ways out. The payer never looked at whether your nutrition visit was covered; it only looked at the date the claim arrived. The good news is that the few ways out are concrete, and the prevention is simple enough to become a weekly habit.
What CO-29 means
The X12 CARC list defines code 29 as:
"The time limit for filing has expired."
Every payer sets a deadline for receiving a claim, counted from the date of service (or, for secondary claims, often from the primary payer's remittance date). Miss it and the claim is denied as CO-29. The CO group code puts the loss on the provider.
Filing limits: Medicare vs commercial
- Medicare Part B: the claim must be filed no later than one calendar year after the date of service (42 CFR 424.44).
- Medicare Advantage, Medicaid and commercial plans: set by the payer and your contract. Deadlines of 90, 120 or 180 days from the date of service are common, some are longer, and a few are shorter. The number that binds you is the one in your contract or the payer's provider manual, not a list on the internet. Our timely filing limits by payer explains where to find it.
- Corrected claims and appeals have their own windows, usually counted from the original remittance date.
How nutrition claims end up past the deadline
These are the patterns we see most in dietitian practices:
- The claim was rejected and nobody noticed. A missing member ID prefix or referring NPI bounced the claim at the clearinghouse. It sat in a rejection queue for months. A rejected claim does not count as filed. This is by far the most common path; see claim rejection vs denial.
- The visit was never billed. The note was signed, but the claim was never created, often for visits charted late or moved between tools.
- It went to the wrong payer first. An out-of-state Blue member billed to the home plan, or a Medicare Advantage member billed to Medicare, came back CO-109. By the time it reached the right payer, the window had closed.
- Secondary claims waited on the primary. The secondary deadline often runs from the primary's remit, and that date is easy to lose.
- Retroactive changes. The patient's coverage was reinstated or changed retroactively, and the claim was filed to the new payer late.
Can you still get paid? The exceptions that work
Proof of timely filing
This is the only strong appeal for most CO-29s. You need a document showing the payer (or its designated clearinghouse) accepted the claim within the window:
- A clearinghouse acceptance report or payer acknowledgment (277CA) that shows the claim was accepted by the payer, with the date and claim identifiers.
- A prior remittance or EOB for the same claim dated inside the window (for example, an earlier denial for a different reason).
- A payer portal record of an accepted submission.
A screenshot that says "sent" or a practice-management log is weak. A rejection report is proof that the claim was not accepted.
Recognized exceptions
- Medicare extends the deadline for a limited set of situations listed in 42 CFR 424.44, including an error or misrepresentation by a Medicare contractor or employee, and retroactive Medicare entitlement. Each has its own conditions and extended deadline.
- Commercial and Medicaid plans often allow exceptions for retroactive eligibility, coordination-of-benefits delays or payer error. They are in the provider manual; if they are not, ask provider services in writing.
How to file the appeal
- Pull the proof (acceptance report, earlier remit) and highlight the date and claim number.
- Write a short cover letter: claim, date of service, original submission date, the proof attached, and the exception if one applies.
- Submit through the payer's reconsideration or appeal channel within its appeal window. The step-by-step is in how to appeal a denied nutrition claim.
Can you bill the patient?
In network, generally no. Filing on time is the provider's job under the contract, and CO-29 assigns the loss to the provider. Out of network, it depends on your agreement with the patient and state law. Either way, a patient who paid their copay on time did nothing wrong.
The prevention system
- Bill within days. The shorter the gap between visit and claim, the more room you have for a rejection, a correction and a resubmission.
- Check rejections weekly. Every rejected claim gets fixed and resent within the week. Accepted is the only status that stops the clock.
- Keep acceptance reports. Download or retain the clearinghouse and 277CA acknowledgments so proof exists when you need it. Our clearinghouse guide covers where to find them.
- Track every visit to a claim. Once a week, compare signed notes against claims created. A visit without a claim is revenue with a timer running.
- Calendar the short deadlines. Know which of your payers have the shortest windows and work those claims first. Our timely filing calculator does the date math.
For every other nutrition denial code, see the denial code lookup.