Claim adjustment reason code
CO-29: Time limit for filing has expired
CO-29 means: The time limit for filing has expired. The claim arrived after the payer’s filing deadline. This one is usually terminal, which is why it deserves attention before it happens rather than after.
Read the group code before you act on this
29 is the reason. The CO in front of it is the group code, a separate field on the remittance, and it is the one that decides who owes the money: CO means contractual obligation — the payer says the amount is not billable to anybody, and it is written off unless the denial itself is overturned. You may not bill the patient. What the other group codes mean.
What causes CO-29?
- The claim sat in a hold queue or a scrubber rejection nobody worked
- It was originally submitted to the wrong payer and the clock kept running
- Coordination of benefits was unresolved and the secondary was filed late
- The practice assumed a 365 day window when the payer contract says 90
How do you fix a CO-29 denial?
- Check whether you can prove timely submission: a clearinghouse acceptance report with a date inside the window will overturn many of these
- If the delay was caused by the payer, for example an eligibility or COB error on their side, appeal with the evidence and cite it
- If it was filed to the wrong payer first, many contracts allow the clock to run from the primary’s remittance date — check the contract, not the general rule
- Where it is genuinely late and unprovable, write it off and move on rather than spending forty dollars of labour on it
Can CO-29 be prevented?
Every CO-29 is a claim that was already worked once and then abandoned. An aged AR queue that nobody calls on generates these steadily and silently.
A denial like this one is the recurring cost that medical billing outsourcing is built to take off your desk — a dedicated seat working the queue instead of it waiting for whoever has a free hour.
Who does this work
A ar calling & denial management seat at $1,700 per seat per month works this queue full time, during your business hours, inside your own system. Every call is logged with the payer reference number and the outcome, and every Friday you get it in writing.
Specialties that name this among their costliest
These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.
- Primary CareLow-dollar denials — the patient assigned to a different primary care provider, a wrong place of service — left in the queue as not worth the call, then aged past timely filing.
What leaving it costs
Working a denied claim costs $57.23 per denied claim in administrative time (source) — before any of it is recovered, and whether or not it ever is.
Payers ultimately pay roughly 90% of claims even while using an initial denial to slow payment (source), so the reason one sits is rarely that nobody knows how to work it. Put your own denial count in.
Questions
What does denial code CO-29 mean?
The time limit for filing has expired. In plain terms: The claim arrived after the payer’s filing deadline. This one is usually terminal, which is why it deserves attention before it happens rather than after.
What causes CO-29?
The claim sat in a hold queue or a scrubber rejection nobody worked. It was originally submitted to the wrong payer and the clock kept running. Coordination of benefits was unresolved and the secondary was filed late. The practice assumed a 365 day window when the payer contract says 90.
How do you fix a CO-29 denial?
Check whether you can prove timely submission: a clearinghouse acceptance report with a date inside the window will overturn many of these. If the delay was caused by the payer, for example an eligibility or COB error on their side, appeal with the evidence and cite it. If it was filed to the wrong payer first, many contracts allow the clock to run from the primary’s remittance date — check the contract, not the general rule. Where it is genuinely late and unprovable, write it off and move on rather than spending forty dollars of labour on it.
Can CO-29 be prevented?
Every CO-29 is a claim that was already worked once and then abandoned. An aged AR queue that nobody calls on generates these steadily and silently.
Is CO-29 the same as PR-29?
Same reason, different group code. The number 29 is the reason: The claim arrived after the payer’s filing deadline. This one is usually terminal, which is why it deserves attention before it happens rather than after. The prefix says who carries the amount. CO means contractual obligation — the payer says the amount is not billable to anybody, and it is written off unless the denial itself is overturned. PR-29 is the same reason assigned to patient responsibility — the payer says the amount is owed by the patient, and it is billed to them. Read the prefix before the number: it decides whether you appeal, write off, or bill the patient.
What about the codes next to CO-29?
CO-28 and CO-30 are separate codes and this site does not yet cover them. The authoritative list is the X12 Claim Adjustment Reason Codes at x12.org/codes/claim-adjustment-reason-codes; a code is only described here once its official text, causes and fix have been written and checked.
Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.
Last updated 2026-09-14. This is operational guidance drawn from payer remittance practice, not legal, coding or reimbursement advice. Payer-specific rules vary and change; confirm against the payer’s own policy before acting on a specific claim.
Other denial codes
- CO-286 — Appeal time limits not met
- OA-23 — Prior payer’s adjudication
- CO-136 — Failure to follow the prior payer’s coverage rules
- CO-185 — Rendering provider not eligible
- CO-B7 — Provider not certified or eligible on this date
- CO-10 — Diagnosis inconsistent with patient gender
- How to overturn a timely filing denial
- Why prior authorizations get delayed, and how to stop it
- How denial management works, and what it costs to skip
Next step
Is CO-29 one of the denials costing you most?
Send a ninety-day denial report and an aged AR summary, with no patient identifiers. Within two working days you get a written summary of which denial reasons are costing you most and what is recoverable.
Or write to ops@softhomeglobal.com