Timely Filing Limits by Payer (2026 Reference)

Short answer

A timely filing denial is one of the few denial categories that has almost no appeal path. Once the clock runs out, the payer has a categorical defense: the claim was late. Medicare is governed by federal statute — providers have exactly 12 calendar months from the date of service, with only two narrow exceptions (administrative error by a government employee and retroactive Medicare entitlement). Authority comes from 42 C.F.R. § 424.44 and the CMS Medicare Claims Processing Manual, Pub. 100-04, Chapter 1, Section 70. Commercial payers set their own windows, commonly 90 to 180 days for in-network providers, but those numbers change by plan, state, and the specific language in your contract. Medicaid fee-for-service windows are set by each state and range from under 90 days to one full year. For billing companies, the filing clock runs against dozens or hundreds of practices at once, making it a tracking problem as much as a billing problem.

What timely filing is and why it matters

Every claim has a deadline by which the payer must receive it. Miss that deadline and the payer denies the claim with CARC 29 — "The time limit for filing has expired." That denial is almost always final.

What makes timely filing different from most other denial types is that correctness of the underlying claim is irrelevant. A claim can be perfectly coded, properly authorized, and submitted to the right payer — and still be denied if it arrives one day past the window. The payer does not owe payment. In most cases the provider cannot collect from the patient either, because writing off the balance is required by participating provider agreements. The revenue is simply gone.

That makes timely filing a category of unappealable revenue leak — meaning the standard denial management toolkit (write a letter, send the record, appeal to a medical director) generally does not apply. The only path to recovery is proving that the original claim was submitted within the window, or that a recognized exception applies.

For a billing company managing dozens of practices, the risk compounds. Each practice has different payers. Each payer has a different window. Some windows are measured from date of service; others from date of discharge. The clearinghouse adds transmission time. Rejections reset the clock for some payers and do not reset it for others.

How the filing clock is measured

The clock typically starts on the date of service (DOS) — the day the patient received care. For inpatient facility claims with multiple covered days, payers generally start the clock from the last date of service (the "through" date on the claim), not the first day of admission. Check the specific payer's policy because a few measure from discharge date rather than last date of service, which can differ by one or two days.

The clock stops when the payer receives a processable claim — not when you press send in your billing software. That distinction matters. Electronic claims travel through a clearinghouse, which transmits the claim to the payer's EDI gateway. Payer receipt of a processable 837 is what counts, not the clearinghouse submission timestamp.

A clearinghouse 999 acknowledgment (functional acknowledgment) confirms the file was received and structurally valid. A 277CA transaction from the payer confirms that the payer accepted the claim for processing. Between those two points sits the risk. If the clearinghouse holds the claim for scrubbing, or the payer rejects it with a 277CA reject, the clock has not stopped — and you may be working against a deadline you thought was already met.

For paper claims, the payer's mailroom date stamp is the receipt date. Certified mail with return receipt provides proof of that date and is the practical minimum for any paper claim close to a deadline.

Payer reference table

The window shown for each commercial payer is a commonly cited default. The number that controls your claim is in your provider contract and the current version of that payer's provider manual. 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 filing window set by federal statute and applies uniformly.

Cigna's in-network and out-of-network windows are cited directly from Cigna's published provider-facing policy page. All other commercial windows in this table should be treated as illustrative order-of-magnitude guidance until you confirm them in your current payer contract and the payer's current provider manual. Commercial provider manuals can change with 30 days' notice; contracts may have language that controls over the manual.

Proof of timely filing and how to document it

When you did submit within the window but the payer denies CO-29 anyway — often because of a processing error on their end — proof of timely filing is what gets the denial overturned. What counts as proof varies by payer, but the following set of documents covers most situations:

• 277CA acceptance from the payer (not just the clearinghouse 999) showing the claim was accepted for processing, dated within the filing window
• Clearinghouse transmission report showing the date the file was sent to the payer's EDI gateway
• EDI 837 submission confirmation with a timestamp
• For paper claims: certified mail receipt or overnight delivery proof with date stamp

The 999 functional acknowledgment from the clearinghouse is not sufficient on its own. It confirms the file was received by the clearinghouse, not by the payer. The 277CA is the document that shows payer acceptance.

Store these records at the claim level. If you are relying on clearinghouse reports that aggregate hundreds of claims into a single file, you need a way to pull the per-claim timestamp when a CO-29 lands six months later. Searching a bulk transmission log mid-appeal is the wrong time to discover you cannot isolate the proof.

Recognized exceptions to the filing deadline

Medicare exceptions

Medicare recognizes two narrow 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 processing 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 receives notification of Medicare coverage that is retroactive to or before the date of service, the filing window extends to six months after the notice of entitlement.

Medicare has no general hardship exception, no force majeure exception, and no "the clearinghouse was down" exception. If the missed deadline does not fit one of those two categories, the denial is final.

For Medicare, a CO-29 denial requires a reopening request to the MAC, not a standard redetermination. The process and required forms depend on the MAC servicing your region.

Commercial payer exceptions

Commercial payers generally recognize a broader (but still narrow) set of exceptions:

• Coordination of benefits: when a commercial plan is secondary, the filing window for the secondary claim often starts from the date of the primary payer's explanation of benefits (EOB), not the date of service. Verify this with each payer — the COB exception is common but not universal, and the language in the EOB remittance date is what governs.
• Retroactive eligibility: if coverage was established or terminated retroactively after the service date, most payers allow a new filing window measured from the date eligibility was confirmed.
• Provider error corrections: some payers allow an extended window when a claim was originally submitted within the window but returned or rejected for a correctable error. Whether a clearinghouse rejection resets the clock depends entirely on the payer contract. Do not assume it does.
• State insurance regulations: a number of states set minimum filing windows by statute or regulation that supersede shorter contractual periods. California is a notable example. If your state has a longer statutory minimum, the state minimum controls, but you need to know this in advance — payers will not volunteer it.

How to appeal a timely filing denial

The relevant CARC is CO-29 ("The time limit for filing has expired"). The group code CO means the contractual obligation is on the provider, which is why most CO-29 denials are final without proof of timely original submission.

The appeal path depends on whether you have proof:

If you have proof of timely original submission (a 277CA dated within the window, or clearinghouse transmission records), submit an appeal or reconsideration with that proof attached. Most payers will overturn CO-29 when the proof is clean and dated. Frame the appeal as a payer processing error, not a request for an extension.

If you do not have clean proof of original submission, assess whether a recognized exception applies — COB timing, retroactive eligibility, or a verified administrative error. If none apply, write off the balance. Spending billing time on an appeal without proof or a cognizable exception is time that will not produce revenue.

For Medicare CO-29 denials: file a reopening request with your MAC. The standard redetermination form does not apply. Attach whatever documentation supports the exception claim.

Document the outcome either way. Whether you recover the claim or write it off, the data feeds the process improvement that prevents the next one.

The billing company tracking problem

A solo practice billing one payer watches one filing window. A billing company with 30 client practices, billing 15 payers each, is watching potentially hundreds of claim deadlines in motion at any given time.

The practical risks in that environment:

• Rejections from the clearinghouse reset the age of a claim in the billing software, but do not reset the filing clock with the payer. A claim rejected on day 60 and resubmitted on day 95 may already be out-of-window if the payer uses a 90-day limit.
• Practices that run insurance eligibility close to filing — including retroactive eligibility confirmation for visits that occurred months earlier — often generate claims that are close to the window before the first submission attempt.
• Staff turnover at a client practice can create a gap where claims are not submitted for weeks. By the time the billing company inherits the backlog, some claims are already at risk.
• Payer contract terms differ across client practices. A large group practice may have negotiated a 180-day window with a payer that gives most in-network providers 90 days. Applying a uniform rule across all clients produces errors in both directions.

The only structural defense is a system that tracks age from date of service independent of claim status — one that flags approaching deadlines before they become CO-29 denials, across all client practices at once. Clearinghouse portals expose this data per practice, not across the whole book of business. A billing software 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 structure. The work queue surfaces claims by days-remaining-to-file across every client practice in the book of business, not per practice in isolation. When a claim sits in an unsubmitted or rejected state and the filing window is narrowing, it surfaces in the queue with enough lead time to act.

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

Medi does not predict which payers will deny for timely filing, guarantee recovery on late claims, or replace the contract-level verification that each practice needs to do with each payer. What it does is reduce the operational gap between "we know the rule" and "we catch the claim before the clock runs out."

For more context on how denial tracking fits into the broader workflow, see the denial management workflow guide. To see how the work queue operates across a multi-practice book of business, schedule a walkthrough.

When Medi is not the right fit

Medi is designed for billing companies that handle revenue cycle work on behalf of multiple client practices — claims, ERA posting, denial follow-up, A/R, and work queues across the book of business.

Medi is not the right fit if:

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

If you are a billing company and the filing window tracking problem resonates, Medi is worth a look. If you are 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, and the answer matters more than most billers realize. A clearinghouse rejection means the clearinghouse rejected the claim before it reached the payer. Since the payer never received a processable claim, the payer's filing window has not been stopped. When the corrected claim reaches the payer, it will be evaluated against the original date of service.

Some payers acknowledge that a documented clearinghouse rejection — with timestamps showing the original attempt was within the window — supports a timely filing appeal when the corrected resubmission falls outside the window. Others take a strict position: the receipt date of the accepted claim is what governs. Your contract language and the payer's published policy control. Before assuming a rejection extends your window, pull the payer's specific policy and document the original transmission date, the rejection acknowledgment, and the corrected resubmission date for every claim that comes close to the deadline. That documentation 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 claims where a commercial plan is secondary, most payers start the filing window from the date of the primary EOB rather than the date of service. The practical effect is that you can bill the primary payer, wait for the EOB, and then bill the secondary — without the date-of-service clock consuming the entire window during that waiting period.

However, this is not a universal rule, and the triggering event varies. Some payers use the date of the primary EOB. Others use the date you received the EOB. A few use the date of service regardless and simply allow a longer window for COB claims. Each payer's contract or provider manual specifies which applies. For Medicare as secondary payer, CMS guidance allows filing up to 12 months from the date of the primary EOB when Medicare is secondary — the Medicare manual section for this is CMS IOM Pub. 100-05. In all cases, retain a copy of the primary EOB as part of the COB claim documentation. It is both the triggering document for the window and the required attachment for most secondary submissions.

Can a timely filing denial for Medicare be appealed if we have no proof of original submission?

For Medicare Original, the answer is almost always no — not through the standard appeal process. Medicare's CO-29 denial has no appeal rights under the standard redetermination and reconsideration process unless you can demonstrate that 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 general hardship exception, and neither covers missed submissions caused by internal billing errors, staff turnover, or clearinghouse issues.

If an exception applies, the mechanism is a reopening request to the Medicare Administrative Contractor for your region, not a standard redetermination. The applicable CMS guidance is in IOM Pub. 100-04, Chapter 1, Section 70.7. Without a qualifying exception and supporting documentation, the denial is final and the amount must be written off. For commercial payers, the threshold is lower — many will consider proof of extenuating circumstances even without a clean submission timestamp — but each payer's appeal policy governs what they will accept.

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

At minimum, retain the following for every electronic claim at the time of original submission: the 999 functional acknowledgment from the clearinghouse confirming the file was received and structurally valid; the 277CA transaction from the payer confirming the claim was accepted for processing; and the clearinghouse transmission report showing the date and time the claim was forwarded to the payer's EDI gateway. The 277CA is the most important document. It is the payer's confirmation of receipt of a processable claim, and it carries a date. That date is what you cite in a CO-29 appeal.

For paper claims, retain the certified mail receipt or overnight tracking confirmation showing the delivery date. Store all of this at the claim level — not in a bulk transmission log — so it is retrievable when a CO-29 comes back months later. Rebuild-on-demand from an archived bulk file is slow and error-prone under time pressure. A denial management system that links the submission history to the claim record saves that search cost when it matters most.

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

Medicare Advantage plans are administered by private insurers approved by CMS. Each plan sets its own timely filing window, which may be shorter than Medicare's 12-month statutory standard. CMS regulations require that MA plans provide at least one calendar year for clean claims, but plans are permitted to set shorter windows in some circumstances, and plan-specific contracts may differ. In practice, MA plan windows vary — some mirror the 12-month Medicare standard, others set shorter windows for specific claim types or provider categories.

The operational implication is that treating all Medicare-billed claims as having a 12-month window is a mistake if the practice participates in any MA plans. Each MA plan's provider manual and your contract are the governing documents. When a practice joins a new MA plan, pulling the timely filing section of the provider manual is a first-day billing setup task — the same way you confirm the billing NPI, the claim address, and the authorization requirements. Failing to do that and discovering a shorter window after a denial is a preventable revenue leak.