Timely filing limits by dental payer — and how to fight a CO-29 denial
What the common filing windows are, why "the time limit has expired" is often wrong, and how to prove you filed on time.
A timely-filing denial (CARC CO-29, "the time limit for filing has expired") is one of the most frustrating — and most reversible — denials in dental billing. Payers deny for late filing readily, but a large share of those claims were filed on time and denied anyway because of a payer-ID error, a coordination-of-benefits delay, or a lost transmission. When your records show the claim went out inside the window, CO-29 is appealable.
Common timely-filing windows
Filing limits vary by payer, plan, and state — these are commonly cited figures, not guarantees. Always confirm the exact window in the payer's provider manual before you rely on it.
| Payer | Commonly cited limit | Notes |
|---|---|---|
| Delta Dental | ~12 months | Varies by Delta member company, plan, and state. |
| Cigna Dental | 90 days (par) | 180–365 days for non-participating providers. |
| Aetna | ~120 days | Up to 180 days–1 year for some employer and MA plans. |
| UnitedHealthcare | ~90 days | Often a shorter preferred window; plan-specific. |
| MetLife | ~90–180 days | Commercial range; confirm per plan. |
| Medicare (Part A/B) | 12 months | CMS-mandated one-calendar-year deadline from date of service. |
| Medicare Advantage | ~90–120 days | Set by the MA plan, not CMS — often much shorter. |
| Medicaid | 90 days–1 year | Varies by state program. |
When CO-29 is worth appealing
- You filed within the window. The clearinghouse or portal report shows the original transmission date inside the limit — the strongest possible proof.
- Proof of prior timely filing. The claim was submitted on time, denied or lost for another reason, and re-filed — many payers count the original date.
- Coordination of benefits. The delay was caused by waiting on the primary payer's EOB; most payers extend the window in COB cases.
- Wrong payer ID / claim routing. A claim sent to the wrong payer within the window and rerouted often still qualifies.
How to prove it
The evidence that overturns CO-29 is the submission record: the clearinghouse acknowledgment (277CA), the payer-portal confirmation, or the batch report showing the claim's original transmission date. Attach it, reference the date explicitly, and cite the payer's own filing window. Keep the appeal factual: "Claim #… was filed on … , within the plan's …-day window (attached). We request reprocessing."
Frequently asked questions
What is CO-29?
CARC CO-29 means "the time limit for filing has expired." If the claim was actually filed within the window, it's appealable — prove the original filing date.
What is the timely filing limit for Delta Dental?
Commonly about 12 months from the date of service, but it varies by the specific Delta company, plan, and state. Confirm in the plan's provider manual.
How do I appeal a CO-29 denial?
Attach the submission report showing the original transmission date within the window (or COB / rerouting evidence) and reference it in the appeal.
Sources
- CMS: Medicare Part A/B claims must be filed within one calendar year of the date of service.
- X12, Claim Adjustment Reason Codes (CO-29).
- Payer filing windows compiled from published medical/dental billing references, 2025; figures vary by plan and state and must be verified per payer.
General information, not billing or legal advice. Filing limits change and vary by plan, state, and contract — always verify in the payer's provider manual.
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