Denial code · group CO
CO-29: The claim arrived after the payer's deadline for filing an original or corrected claim
Short answer
CO-29 means the claim reached the payer after its filing limit, counted from the date of service or, for some secondary claims, from the primary's remittance. The way back is proof of timely filing: a payer acceptance on the 277CA, an earlier remittance, or a payer rejection report where the payer's manual accepts one (Texas Medicaid does, UnitedHealthcare does not). Without proof it is a contractual write-off.
Look up other codes in the denial code library.
Last reviewed by the Remitwright billing team. Editorial policy
Group CO means contractual obligation: the balance is written off, not billed to the patient. The number is the reason; the two-letter group says who carries the balance.
Common causes
A rejection nobody worked
The clearinghouse or the payer's front end rejected the claim on the 277CA for a formatting or identifier error, the rejection report sat unread, and the payer never adjudicated the claim. When someone finds it months later the window has closed. To the payer, the first claim it received is the late one.
A corrected claim after the correction window
The original was filed on time and denied for something fixable. The correction went out after the payer's corrected-claim deadline, which many payers count from the remittance date of the original denial rather than from the date of service.
A wrong-payer round trip
The claim went to a payer that returned it CO-109 or CO-22, and the correct payer did not see it until after its own limit. The correct payer counts from the date of service, not from the day you learned who it was.
A late secondary claim
The primary paid slowly or the primary's 835 was never posted, and the secondary claim went out after the secondary's limit. Some payers count secondary claims from the primary remittance date, others from the date of service, and the difference decides whether this is appealable.
Eligibility or coverage found late
The patient's coverage was unknown or disputed at the time of service, or retroactive eligibility was granted later. The claim could not have been filed on time, which is one of the few arguments payers accept.
The limit was shorter than you assumed
Filing limits vary by payer, plan type and contract. Medicare requires claims to be filed no later than 12 months, or one full calendar year, after the date of service unless an exception applies. A commercial or Medicaid contract can set a much shorter limit, and the same payer can run different limits for different products.
How to fix it and resubmit
- 1
Find the proof before you write the appeal
Pull the clearinghouse acceptance report (the 999 and the 277CA) showing the payer accepted the claim, or the payer's own denial notice, or its rejection report if the payer's manual accepts one, dated inside the window. For a secondary claim, pull the primary's 835 with its remittance date. A screenshot of your practice management system's submission date is rarely accepted on its own.
- 2
File a timely filing reconsideration with the proof attached
Use the payer's reconsideration or appeal form, state the date the claim was first received by the payer, attach the acceptance report or earlier remittance, and ask the payer to reprocess. Keep it to the facts; the payer is checking a date, not a story.
- 3
Argue an exception when the claim could not have been filed
Retroactive eligibility, payer error, a wrong-payer return with proof of the earlier filing, or a member who did not disclose coverage are the usual grounds. Each payer defines its own exceptions, so quote the payer's manual rather than another payer's rule.
- 4
Write it off correctly when there is no proof
A CO-29 without evidence is a contractual adjustment. Under most participating contracts you cannot bill the patient for a claim the practice filed late. Code the write-off so the cause is visible on your denial reports.
- 5
Check the rest of the batch
A late claim rarely travels alone. Search the clearinghouse rejection reports and the unbilled and unacknowledged claim lists for the same period and payer, and file whatever is still inside a window today.
How to prevent it
- Rejection reports from the clearinghouse and the 277CA worked every business day, with every rejected claim fixed and resent inside the week
- A filing-limit table per payer and plan type in the practice management system, with alerts on unbilled and unacknowledged claims well before each limit
- Secondary claims generated automatically when the primary 835 posts, so the secondary window is never the one that closes first
- Acceptance reports stored with the claim, so proof of timely filing is retrievable without a search
- A weekly aging review of claims with no payer acknowledgement, which catches the ones that never left
A CO-29 that started as a clearinghouse rejection
An urgent care sends a batch of claims to a commercial payer in March. The clearinghouse rejects the batch for an invalid taxonomy code and posts the rejection to a report nobody reads. In August an accounts receivable review finds the claims unpaid, fixes the taxonomy and resubmits. The payer denies every claim CO-29; the practice's contract sets a 90-day filing limit from the date of service. The practice has only a clearinghouse rejection, not a payer acceptance, so no proof of timely filing exists and the balances are written off. The next week the clinic assigns the daily rejection report to a named person. This is a hypothetical example.
Official text: the X12 claim adjustment reason code list. The meaning above is our paraphrase for billers; the list is the authority.
FAQ
Questions about CO-29
What counts as proof of timely filing?
How long is the timely filing limit?
Can I bill the patient after a CO-29?
Does a rejected claim count as filed?
The payer took months to deny and now my correction is late. What can I do?
Next step
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