The timely filing limit is not merely a flexible recommendation; it is a contractual deadline. Failure to meet it results in one of the most difficult denials to overturn in medical billing the CO-29 denial which is almost never reversed without documentary evidence proving the claim was actually submitted on time. Furthermore, Aetna’s filing windows are not uniform across its product lines, making it risky to rely on a single "90-day" or "120-day" rule of thumb. Aetna’s timely filing limit for 2026 are detailed below.

The Standard Commercial Limit: 120 Days

For the majority of in-network commercial and PPO providers, Aetna’s standard timeframe for the timely filing of claims is 120 days from the date of service. Out-of-network providers typically have a longer window, usually 180 days from the date of service. Aetna has not announced major structural changes to these timeframes for 2026; however, exact figures may vary based on the specific provider contract and state regulations, meaning the participation agreement governing your practice takes precedence over any general industry figure.

Aetna Medicare Advantage: A Different Clock Entirely

This is the distinction that often confuses most billing teams: Aetna Medicare Advantage claims are subject to a 365-day timely filing limit from the date of service, rather than the 120-day limit applicable to commercial plans. Since CMS establishes a national minimum deadline of 365 days for Medicare Advantage plans, Aetna’s timely filing limit for these plans aligns with that federal standard as opposed to the terms of the company's own commercial contracts. A claim denied for missing the filing limit even if submitted within three or four months of Medicare Advantage care is highly likely to be the result of the erroneous application of a commercial rule rather than a legitimate denial; therefore, it is worth appealing based solely on this argument.

Aetna Medicaid Managed Care (Aetna Better Health)

Aetna Better Health plans, including Aetna Better Health Kids, generally allow a 180-day window from the date of service for the initial claim submission. For inpatient hospital claims, this period typically begins on the date of discharge rather than the date of admission. State-specific Medicaid regulations may alter this timeframe; therefore, it is advisable to verify the rules applicable to the Aetna Better Health contract in your state.

Corrected and Resubmitted Claims

Generally, corrected claims are subject to a longer filing window than initial submissions: typically 365 days from the original date of service or for certain types of plans 365 days from the date of the provider's Remittance Advice, provided the original claim was submitted on time. This distinction is important: a corrected claim submitted late does not gain a new 120-day period simply because it is a correction; rather, the original filing timeframe is extended, not reset.

Appeals and Reconsiderations

Timely filing limits for appeals with Aetna often differ from those for the initial claim; generally, they range from 60 to 180 days from the date of the denial or determination, depending on the plan type and whether the claim is commercial, Medicare Advantage, or Medicaid. Specifically for Medicare Advantage Part C Level 1 redeterminations, a 65-day limit applies following the denial notice, after which the case may be automatically forwarded to an Independent Review Entity, if applicable.

Secondary and Coordination of Benefits (COB) Claims

Timeframes for secondary claims are governed by their own specific rules; generally, they are calculated based on the date shown on the primary payer's Explanation of Benefits (EOB), rather than the original date of service. For Aetna Medicare Advantage secondary claims, there is typically a 120-day window starting from the primary EOB date; conversely, Medicare crossover claims where Aetna acts as the secondary payer to Medicare may allow for a period of up to 36 months from the original submission date to Medicare, depending on the circumstances.

Quick Reference: Aetna Timely Filing Limits 2026

These figures reflect Aetna's standard policy; however, the plan type, state regulations, and your specific provider agreement may alter the exact figure. Therefore, always verify the information in your participation agreement before treating any of these figures as final.

Why CO-29 Denials Are So Hard to Recover

A rejection with code CO-29 indicates that the payer has determined the claim was received beyond the filing limit; overturning this decision requires proof such as a clearinghouse acceptance report, proof of certified mailing, or documented evidence that the delay was caused by Aetna’s own system (e.g., an eligibility error) rather than the provider's office. Without such proof, the claim is typically closed permanently, which is why prevention is more important than an appeal strategy in this instance.

How Practices Protect Themselves From Timely Filing Losses

1. Track filing deadlines based on the specific payer and plan type, rather than applying a single, blanket deadline across your entire payer portfolio.
2. Submit claims shortly after care is provided rather than waiting until the end of the billing cycle to allow a buffer for potential coding delays or clearinghouse rejections.
3. Verify whether the patient’s plan is a commercial plan or Medicare Advantage before assuming which deadline applies; the difference between the two can exceed 240 days.
4. Retain clearinghouse submission records for all claims, as these serve as the primary evidence needed to contest an improper denial with code CO-29.
5. Review your participation agreement with Aetna annually, as specific contract terms may differ from the general industry figures mentioned above.

The Takeaway

Aetna’s timely filing limits are not defined by a single figure; rather, they consist of a set of rules that vary significantly depending on the plan type. The 120-day standard for commercial plans often applied by default does not apply to Medicare Advantage, Medicaid, corrected claims, or appeals. A denial based on code CO-29 is one of the few billing errors that is virtually irreversible once it occurs; therefore, knowing the specific deadline for each claim is one of the most valuable practices a billing team can adopt.

ESOFTX, Inc. helps medical practices manage payer-specific filing deadlines, reduce avoidable CO-29 denials, and streamline the claims workflow within the revenue cycle, thereby preventing unnecessary revenue loss. If you are receiving denials for untimely filing on your Aetna claims, we would be happy to analyze your workflow.