CO-29 denial code
The claim was filed after the payer's deadline. Timely filing limits are contractual, they are strict, and this denial is usually final.
CO — Contractual Obligation. The write-off is yours. You agreed to it in your contract with the payer, and you cannot bill the patient for it.
Why you got it
- 1The claim genuinely was submitted late.
- 2The claim was submitted on time but to the wrong payer, and the clock kept running.
- 3The claim was rejected at the clearinghouse and never actually reached the payer — a rejection is not a submission.
- 4The original was submitted on time but a corrected claim was filed after the limit.
How do I fix a CO-29 denial?
- Find proof of timely submission. A clearinghouse acknowledgement showing the payer accepted the claim within the window is the thing that overturns this.
- If it was rejected rather than denied, the rejection report is your evidence that you tried — but it may also be evidence you never actually filed.
- Appeal with the documentation. Without proof, this one usually stands.
How to stop the next one
Watch the rejections, not just the denials. A claim sitting in a clearinghouse rejection queue is a claim that was never filed, and the timely filing clock does not care.
Our diagnosis scrubber will not catch this one. CO-29 is driven by procedure codes, modifiers, or eligibility rather than by the diagnosis set — and procedure-side checking needs an AMA CPT licence we do not hold yet. We would rather tell you that than sell you a tool that quietly misses your most common denial.
If denials like this are a volume problem rather than a one-off, the denial management page explains how the paid workspace catches the coding causes on every claim, and the free ICD-10-CM lookup shows the coding notes behind any diagnosis code on the remittance.