CO-29
Depends on the detailsTime limit for filing has expired
Group CO — Contractual Obligation — an adjustment tied to the contract between the insurer and the provider. You usually cannot be billed for a CO amount.
CO-29 means the claim was filed after the plan's timely-filing window (the period a provider has to submit a claim after the date of service). It's about when the claim was submitted, not about your care.
Because it's a Contractual Obligation (CO), this is generally the provider's responsibility — you typically should not be balance-billed because your provider filed the claim late.
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Why you're seeing CO-29
- The provider submitted the claim after the plan's filing deadline.
- The claim was first sent to the wrong payer, using up the filing window.
- A claim was rejected and not corrected and resubmitted in time.
Can you appeal it?
Primarily a provider issue — but appealable with proof of timely submission or good cause, and you generally shouldn't be billed for the provider's late filing.
What to do next
- 1Ask the provider for proof the claim was originally submitted on time (a clearinghouse or submission report).
- 2If there's good cause for the delay (e.g., it went to the wrong payer first), document it.
- 3Make sure you aren't being billed for a denial caused by the provider's late filing.
- 4Appeal with proof of timely filing if one exists.
Evidence that helps
- Clearinghouse or electronic submission reports showing the original filing date.
- Records showing the claim was first sent to another payer.
Frequently asked questions
Can I be billed because my provider filed late?
Generally no. CO-29 is a contractual obligation, meaning the timely-filing rule is between the provider and the plan. If a provider tries to bill you for a claim denied only for late filing, you can dispute it.
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Other common denial codes
Last reviewed July 18, 2026. Denial-code lists (CARC/RARC) are updated three times a year; we review these explanations against the current list.
Sources & references
These explanations are written in plain language and based on the authoritative sources below. Always confirm the specifics against your own plan documents and denial letter.
- ASC X12 — Claim Adjustment Reason Codes (CARC)
The standards body that maintains the official CARC list (the CO/PR codes), updated three times a year.
- CMS / X12 — Remittance Advice Remark Codes (RARC)
The remark codes (N-/M- codes) that accompany a CARC and give the specific reason for an adjustment.
- HealthCare.gov — Appealing a health plan decision
Official overview of internal appeals and external review rights for Marketplace and most private plans.
- Your state's insurance regulator
State agencies enforce external review and consumer protections; find yours via the NAIC directory.
Important: this is not legal or medical advice.
AppealBrain is a free, self-help tool that helps you draft an appeal letter using the information you provide. We are not a law firm, medical provider, or insurance company, and using this tool does not create an attorney–client relationship. Appeal rules and deadlines vary by plan and state — always review your own denial letter and plan documents, and consider consulting a licensed professional for your specific situation. We do not guarantee any outcome.