Timely Filing and Late Bills

Health insurance claims must be submitted within a defined window after care is delivered. When a provider misses that window, the claim is denied — and the question of who absorbs the cost depends on whether the provider is in-network, what your state law requires, and whether the denial can be appealed. Understanding how timely filing works protects you from paying bills that should have been the provider’s problem to resolve.

For the broader context of reading an EOB and understanding denial codes, visit the Reading an EOB and a Medical Bill guide.

What timely filing means and why it exists

Timely filing is the rule that a provider must submit a claim to an insurer within a specific number of days after the date of service. The date of service — the date care was actually delivered — is the starting point for the clock in almost every scenario.

Insurers set timely filing limits to ensure claims are reviewed while records are current, prevent fraud through stale billing, and manage administrative workloads. These limits are written into every provider contract and into the plan’s governing documents.

The timely filing window varies by plan type:

Plan or Program	Typical timely filing window
Commercial / employer-sponsored (most plans)	90 to 365 days from date of service
Medicare (Part A and Part B)	One calendar year from date of service
Medicaid	Varies by state; commonly 90 to 365 days
TRICARE (military)	One year from date of service
Marketplace (ACA) plans	Set in the plan contract; commonly 180 days

These are typical ranges. Your plan’s Summary of Benefits and Coverage, Evidence of Coverage, or Summary Plan Description will state the exact rule that applies to your coverage. When in doubt, your insurer’s member services line can confirm the window.

What happens when a provider files late

When a claim arrives outside the timely filing window, the insurer will deny it. On the EOB, this denial appears as Claim Adjustment Reason Code CO-29: “The time limit for filing has expired.”

The CO group code is significant. CO stands for Contractual Obligation — meaning the write-off is the provider’s responsibility under their contract with the insurer. An in-network provider who files a claim late is generally barred from billing you for the denied amount. The provider absorbed the cost by failing to meet their own administrative obligation.

If you receive a bill from an in-network provider for a service that was denied CO-29, you have grounds to dispute it in writing. Reference the group code, the claim date, and the provider’s contractual write-off obligation.

When a timely filing denial can be appealed

Timely filing denials are not always final. There are circumstances where the denial can be successfully reversed:

The provider has proof of timely submission. If the provider sent the claim on time but it was lost in transit, rejected by a clearinghouse, or sent to the wrong payer address, proof of that original submission — a clearinghouse acceptance receipt, a certified mail receipt, or a fax confirmation page — is usually sufficient to overturn the denial. The insurer cannot penalize the provider for a delay they did not cause.

The insurer provided incorrect billing information. If the insurer gave the provider a wrong address or billing ID that caused the claim to go astray, the denial may be reversed.

Coverage was retroactively applied. When a patient’s coverage was added retroactively — for example, when a Medicaid application was approved months after the date of service — the timely filing clock may be reset to run from the date of coverage confirmation rather than the date of service.

Administrative error. Some insurers will consider appeals that document a bona fide administrative mistake that was not the provider’s fault.

How to appeal a timely filing denial: steps

1. Request the full EOB showing the denial code (CO-29) and the date the claim was received by the insurer.
2. Ask the provider’s billing department whether they have proof of timely submission — clearinghouse receipts, dated fax logs, or electronic submission records.
3. Ask the provider to file an appeal with the insurer, attaching that proof. Most appeals must be filed within a defined window after the denial — often 60 to 180 days.
4. If the provider refuses to appeal and you believe the denial was improper, file a complaint with your state insurance commissioner’s office and, if applicable, with your employer’s benefits administrator.
5. Keep copies of all correspondence, including the denial notice, the appeal letter, and any response.

Documents and terms you’ll see

When a timely filing issue appears on your EOB or in a provider bill, you will encounter these terms:

• Timely filing — the contractual requirement that a claim be submitted within a defined window; failure triggers a denial the provider must absorb if they are in-network
• Date of service — the date care was delivered; the start of the timely filing clock in most cases
• Claim — the formal billing request submitted by the provider; a claim submitted outside the window will be denied
• EOB (Explanation of Benefits) — the document that shows denial reason codes; CO-29 on the EOB indicates a timely filing denial
• Appeal — the formal process for asking the insurer to reconsider a denial; timely filing denials can be appealed if the provider has proof of original timely submission

Protecting yourself from late bills as a patient

You cannot control when a provider submits a claim, but you can take steps to reduce your exposure to late billing disputes:

• Keep your insurance cards and EOBs. If a bill arrives long after the date of service, you will need your EOB to verify what was or was not processed.
• Request a copy of your EOB after each visit. Most insurer member portals post EOBs within days of processing. Check them so you can spot missing claims before the timely filing window closes.
• Follow up on missing EOBs. If you had a procedure and do not receive an EOB from your insurer within six to eight weeks, call member services to check whether a claim was submitted. If no claim was received, notify your provider’s billing department promptly.
• Do not pay a provider bill without reviewing the corresponding EOB. If a bill arrives but you have no EOB, ask your insurer whether a claim was filed and processed.

Out-of-network providers and timely filing

The CO-29 write-off obligation is a contractual protection that applies only to in-network providers. Out-of-network providers do not have a contract with your insurer, so if their claim is denied for late filing, they may still attempt to bill you for the full charge.

Your recourse in that situation depends on your state. Some states have prompt billing statutes that limit how long after care a provider can bill a patient, regardless of network status. Others do not. Contact your state insurance commissioner’s office or a consumer advocacy organization if you are facing a large bill from an out-of-network provider whose claim was denied for late filing.