Timely Filing Limits by Payer (2026 Reference)

Short answer

A timely filing limit is the deadline by which a payer must receive a claim. Miss it and the payer denies with CARC 29, and that denial is almost always final. Medicare is set by federal statute: 12 calendar months from the date of service, with two narrow exceptions (administrative error by a government employee, retroactive Medicare entitlement) under 42 C.F.R. § 424.44 and the CMS Medicare Claims Processing Manual, Pub. 100-04, Chapter 1, § 70. Commercial payers set their own windows, commonly 90 to 180 days in-network, but the number that controls is in your contract and the payer's current provider manual. Medicaid fee-for-service ranges from under 90 days to a full year by state. The table below is the reference; verify every commercial window against your contract before relying on it.

What timely filing is and why it matters

Every claim has a deadline by which the payer must receive it. Miss it and the payer denies with CARC 29, "The time limit for filing has expired."

Timely filing is the rare denial where the correctness of the claim is irrelevant. A claim can be perfectly coded, properly authorized, and sent to the right payer, and still be denied if it arrives one day late. The payer owes nothing, and the provider usually cannot bill the patient either, because participating provider agreements require writing the balance off. The revenue is gone.

That puts it outside the standard denial toolkit. Writing a letter, sending the record, and appealing to a medical director do not apply. The only path to recovery is proving the original claim was submitted within the window, or that a recognized exception applies.

How the filing clock is measured

Payer reference table

The commercial windows below are commonly cited defaults, not facts about your contract. The number that controls your claim is in your provider contract and the payer's current provider manual, and both can change. Verify directly with the payer before relying on any third-party source, including this one. Medicare's 12-month rule is the only window set by federal statute, and it applies uniformly. Where a payer publishes a window (Cigna), it is cited directly; treat everything else as order-of-magnitude until confirmed.

A note on the contract-over-manual order: commercial provider manuals can change with 30 days' notice, and contract language may control over the manual. Confirm both.

Proof of timely filing and how to document it

When you submitted within the window but the payer denies CO-29 anyway, usually a processing error on their end, proof of timely filing is what overturns it. What counts varies by payer; this set covers most situations:

• **277CA acceptance from the payer**, dated within the window. This is the key document — it shows the payer accepted a processable claim, and it carries a date. The clearinghouse 999 confirms only that the file reached the clearinghouse, not the payer, so it is not sufficient on its own.
• **Clearinghouse transmission report** showing the date the file was forwarded to the payer's EDI gateway.
• **EDI 837 submission confirmation** with a timestamp.
• **Paper claims:** certified mail receipt or overnight delivery proof with a date stamp.

Store these at the claim level. If you rely on clearinghouse reports that batch hundreds of claims into one file, you need to pull the per-claim timestamp when a CO-29 lands six months later. Mid-appeal is the wrong time to discover you cannot isolate the proof.

Recognized exceptions to the filing deadline

Medicare exceptions

Medicare recognizes exactly two exceptions under 42 C.F.R. § 424.44(b):

• **Administrative error** by a CMS employee, Medicare Administrative Contractor, or authorized agent of the Department. If a government-side failure caused the missed deadline, the extension runs through the last day of the sixth calendar month after notice of the correction. This is not a general "technical difficulties" exception.
• **Retroactive Medicare entitlement.** When a beneficiary is notified of Medicare coverage retroactive to or before the date of service, the window extends to six months after the notice of entitlement.

There is no hardship exception, no force majeure exception, and no "the clearinghouse was down" exception. If the miss does not fit one of those two, the denial is final. A Medicare CO-29 requires a reopening request to the MAC, not a standard redetermination, and the required forms depend on the MAC for your region.

Commercial payer exceptions

Commercial payers recognize a broader but still narrow set:

• **Coordination of benefits.** When a commercial plan is secondary, the window often starts from the date of the primary payer's EOB, not the date of service. Common but not universal — verify, and note whether the contract keys off the EOB date or the date you received it.
• **Retroactive eligibility.** If coverage was established or terminated retroactively after the service date, most payers allow a new window measured from the date eligibility was confirmed.
• **Provider error corrections.** Some payers extend the window when a claim was submitted in time but returned or rejected for a correctable error. Whether a clearinghouse rejection resets the clock depends entirely on the contract. Do not assume it does.
• **State insurance regulations.** Some states set minimum filing windows by statute that supersede shorter contractual periods (California is one). Where the state minimum is longer, it controls, but you need to know it in advance because payers will not volunteer it.

How to appeal a timely filing denial

The relevant code is CO-29. The CO group code puts the obligation on the provider, which is why most CO-29 denials are final without proof of timely original submission. The path depends on whether you have that proof.

• **With proof** (a 277CA dated within the window, or clearinghouse transmission records): submit an appeal or reconsideration with the proof attached, and frame it as a payer processing error, not a request for an extension. Most payers overturn CO-29 when the proof is clean and dated.
• **Without proof:** assess whether a recognized exception applies (COB timing, retroactive eligibility, verified administrative error). If none does, write off the balance. An appeal without proof or a cognizable exception will not produce revenue.
• **Medicare CO-29:** file a reopening request with your MAC, not a redetermination, and attach whatever supports the exception.

Document the outcome either way. Recovery or write-off, the data feeds the process change that prevents the next one.

The billing company tracking problem

A solo practice watches one filing window. A billing company with 30 client practices billing 15 payers each watches hundreds of deadlines in motion at once. The risks specific to that scale:

• **Rejections age the claim but not the clock.** A clearinghouse rejection resets the claim's age in the billing software but not the filing window with the payer. A claim rejected on day 60 and resubmitted on day 95 is already out-of-window against a 90-day limit.
• **Late eligibility means late first submission.** Practices that confirm eligibility close to filing, including retroactive confirmation for visits months earlier, generate claims already near the window before the first attempt.
• **Staff turnover creates backlogs.** A gap at a client practice where claims sit unsubmitted for weeks means some are at risk by the time the billing company inherits them.
• **Contract terms differ per client.** A large group may have a 180-day window with a payer that gives most in-network providers 90. A uniform rule across clients produces errors in both directions.

The structural defense is a system that tracks age from date of service independent of claim status and flags approaching deadlines across all client practices at once. Clearinghouse portals expose this per practice, not across the whole book. A platform that aggregates it is a different tool.

How Medi helps billing companies track filing deadlines

Medi is built for the multi-practice billing company. The work queue surfaces claims by days-remaining-to-file across every client practice at once, not per practice in isolation. A claim sitting unsubmitted or rejected with a narrowing window appears in the queue with lead time to act.

Denial tracking ties CO-29 denials to the submission history. When one lands, the appeal packet workflow pulls the clearinghouse timestamps and 277CA records for that claim, so the proof-of-filing question is answerable at the denial, not after a manual log search.

Medi does not predict which payers will deny, guarantee recovery on late claims, or replace the contract-level verification each practice owes each payer. It closes the gap between knowing the rule and catching the claim before the clock runs out.

For how denial tracking fits the broader workflow, see the denial management workflow guide. To see the work queue run across a book of business, schedule a walkthrough.

When Medi is not the right fit

Medi is for billing companies running revenue cycle work for multiple client practices: claims, ERA posting, denial follow-up, A/R, and work queues across the book. It is not the right fit if:

• You are a single practice doing your own billing and want a practice management system with scheduling and EHR integration
• Your primary need is clinical documentation, prior authorization, or coding workflows, which sit upstream of where Medi operates
• You need patient scheduling, appointment reminders, or portal messaging as primary features
• You are a clearinghouse looking for a claims routing and translation platform

If the filing-window tracking problem resonates and you bill for multiple practices, Medi is worth a look. If not, there are better-fit tools for your context.

Frequently asked questions

Does a clearinghouse rejection reset the timely filing clock?

It depends on the payer. A clearinghouse rejection means the claim never reached the payer, so the payer's window never stopped, and the corrected claim is evaluated against the original date of service. Some payers accept a documented rejection with timestamps inside the window as support for an appeal when the resubmission falls outside it. Others hold that only the receipt date of the accepted claim governs. Your contract and the payer's published policy decide.

Before assuming a rejection extends your window, pull the payer's policy and document the original transmission date, the rejection acknowledgment, and the corrected resubmission date for every claim near the deadline. That record is the only thing that supports an appeal if the resubmission is late.

What is the filing window for a COB claim when the plan is secondary?

For coordination of benefits where a commercial plan is secondary, most payers start the window from the date of the primary EOB, not the date of service, so you can bill the primary, wait for the EOB, and then bill the secondary without the date-of-service clock consuming the window.

The triggering event varies: some payers use the primary EOB date, some the date you received it, a few use the date of service with a longer COB window. The contract or provider manual specifies which. For Medicare as secondary payer, CMS guidance (IOM Pub. 100-05) allows filing up to 12 months from the date of the primary EOB. Retain the primary EOB either way — it is both the triggering document and the required attachment for most secondary submissions.

Can a Medicare timely filing denial be appealed with no proof of original submission?

For Medicare Original, almost never through the standard process. A CO-29 has no redetermination or reconsideration rights unless one of the two statutory exceptions under 42 C.F.R. § 424.44(b) applies: administrative error by a CMS employee or contractor, or retroactive Medicare entitlement. Neither is a hardship exception, and neither covers misses from internal billing errors, staff turnover, or clearinghouse issues.

If an exception applies, the mechanism is a reopening request to your MAC, not a redetermination; the guidance is IOM Pub. 100-04, Chapter 1, Section 70.7. Without a qualifying exception and documentation, the denial is final and the amount is written off. Commercial payers set a lower bar — many consider extenuating circumstances even without a clean timestamp — but each payer's appeal policy governs.

What documentation should we keep at the claim level to support a timely filing appeal?

For every electronic claim at original submission: the 999 functional acknowledgment from the clearinghouse, the 277CA from the payer confirming the claim was accepted for processing, and the clearinghouse transmission report with the date and time the claim was forwarded to the payer's EDI gateway. The 277CA matters most — it is the payer's confirmation of receipt of a processable claim, and its date is what you cite in a CO-29 appeal. For paper claims, keep the certified mail receipt or overnight tracking with the delivery date.

Store all of it at the claim level, not in a bulk transmission log, so it is retrievable when a CO-29 returns months later. Rebuilding from an archived bulk file is slow and error-prone under time pressure. A denial system that links submission history to the claim record removes that search cost.

How do Medicare Advantage timely filing windows differ from Original Medicare?

Medicare Advantage plans are run by private insurers approved by CMS, and each sets its own window. CMS requires MA plans to allow at least one calendar year for clean claims, but plans may set shorter windows in some circumstances and contracts differ, so in practice windows vary — some mirror the 12-month standard, others are shorter for specific claim types or provider categories.

The implication: treating every Medicare-billed claim as a 12-month window is a mistake if the practice participates in any MA plan. The plan's provider manual and your contract govern. When a practice joins a new MA plan, pulling the timely filing section is a first-day setup task, alongside the billing NPI, claim address, and authorization requirements. Discovering a shorter window after a denial is a preventable revenue leak.