If you have ever had a claim denied with code CO-29, you already know the pain of missing a
timely filing deadline. With Aetna, getting the timing right is not optional — it is the difference
between getting paid and losing revenue entirely. This guide breaks down every key deadline
you need to track in 2026.
What Is a Timely Filing Limit?
A timely filing limit is the maximum number of days a provider has to submit a claim to an
insurance payer after the date of service. Once that window closes, the claim is denied — and
in most cases, that denial is final. Aetna is no different. It enforces strict filing windows
depending on your plan type, provider status, and the state you practice in.
The Standard 120-Day Rule for Initial Claims
For most providers billing Aetna, the standard window for submitting an initial claim is 120 days
from the date of service. This applies to both participating and non-participating providers
across commercial plans. The clock starts ticking on the day the patient receives care — not the
day you prepare the claim or drop it in the mail. Aetna must actually receive the claim within that
window.
There are some important exceptions to note. Medicare Advantage plans follow CMS rules,
which set the floor at 12 months from the date of service. Aetna Better Health Medicaid plans
typically allow 180 days, though this varies by state. Federal Employee plans depend entirely on
the individual contract.
Corrected and Resubmitted Claims
Mistakes happen in billing. The good news is that Aetna does allow corrected claims, but the
rules are stricter than many providers realize.
If your original claim was denied due to a billing or coding error, you have 365 days from the
date of service to submit a corrected version. However, Aetna will only consider this if the late
submission was due to an unusual circumstance and your practice has a consistent track record
of timely filing. Be aware that reimbursement may be reduced by up to 25% in these cases.
For claims denied for non-clinical reasons, resubmission is allowed within 180 days from the
denial date. In Maryland specifically, Aetna Better Health gives providers just 60 days from the
original payment date to dispute a claim.
Secondary Claims and COB Deadlines
When Aetna is the secondary payer, the filing window is tied to the primary payer’s Explanation
of Benefits. For commercial COB claims, providers have 60 days from the primary EOB date to
file with Aetna. For Medicare Advantage secondary claims, the window is either 12 months from
the date of service or 60 days from the primary EOB — whichever comes later.
To file a secondary claim successfully, make sure you have the primary payer’s EOB or
Remittance Advice, the patient’s primary insurance ID, documentation of what the primary payer
paid, and a completed COB form.
Appeals: Know Your Window Before You File
If a claim is denied and you want to appeal, timing is everything here too. Standard appeals for
non-Medicare providers must be filed within 60 calendar days of the denial. Appeals related to
medical necessity or experimental treatment coverage get a longer window of 180 calendar
days. Medicare-contracted providers have 60 days, while non-contracted providers get 65 days.
When Exceptions Apply
Aetna does not forgive routine billing errors, but it does recognize legitimate hardship situations.
Filing deadline exceptions are considered in cases involving FEMA-declared disasters,
retroactive patient eligibility changes, delays from the primary payer in COB situations, and
verified Aetna system outages. Provider credentialing delays may qualify on a case-by-case
basis. Staff errors, software glitches, or patients failing to provide insurance information do not
qualify.
How to Count Your Days Accurately
One of the most common mistakes billing teams make is miscounting the filing window. Every
calendar day counts — weekends, holidays, and all. Start from the actual date of service and
count forward. For a 120-day window starting January 10, 2026, your deadline falls on May 10,
2026. For a 12-month window, simply move the year forward: a March 15, 2026 service date
means your deadline is March 15, 2027.
Final Takeaway
Aetna’s timely filing rules are detailed, but they are manageable if your billing team has a clear
system in place. Always verify the specific deadline for each plan type before submitting,
document your submission dates carefully, and never assume one rule applies to every claim.
When in doubt, submit early — there is no penalty for filing before the deadline expires
