What Happens When a Skilled Nursing Facility Misses a Timely Filing Deadline?

The answer is short and worth stating plainly at the start: the claim is denied, and the revenue cannot be recovered. There is no appeal process that overrides the timely filing deadline. There is no clinical documentation strong enough to reverse it. There is no exception for claims that were denied for other reasons and not corrected in time. If a claim is not filed within Medicare’s 12-month timely filing period from the date of service, payment cannot be recovered.

That finality is what makes timely filing denials different from every other denial category in skilled nursing billing. A medical necessity denial can be appealed. A coding error denial can be corrected and resubmitted. A documentation deficiency denial can be resolved with additional records and a strong appeal letter. A timely filing denial cannot be fixed. The only question is how much revenue was lost and how the billing process allowed it to get there.

This post covers what the timely filing rule requires, what happens operationally when the deadline is missed, the narrow circumstances where an exception may apply, and most importantly the specific billing process failures that allow accounts to reach the deadline without anyone acting on them.

What the Timely Filing Rule Requires

Medicare requires that claims for Part A SNF services be submitted within twelve months of the date of service. The twelve-month window runs from the date the service was provided the first day of the billing period covered by the claim, in the case of SNF Part A claims not from the date the claim was created, not from the date a prior claim was denied, and not from the date the billing team discovered the account.

For corrected claims submitted after a Medicare denial, the timely filing clock does not restart at the denial date. If a claim for services provided in January 2025 is denied in March 2025 and the corrected claim is not submitted until February 2026, the timely filing deadline from the January 2025 service date has passed. The corrected claim will be denied for timely filing regardless of whether the underlying billing error was corrected correctly.

This is the timely filing trap that catches the most accounts in SNF billing operations. Denied claims that enter the rework queue, wait for documentation corrections, get assigned and reassigned during staff transitions, or simply fall below the priority threshold of a busy billing cycle can quietly reach the twelve-month window while still appearing as open accounts in the AR aging report.

What this means for your facility: The date that matters for every denied SNF claim is the original date of service not the denial date. Every denied claim in your AR queue should be evaluated against its original service date, and any claim within 60 days of the twelve-month anniversary of that date should be treated as a billing emergency regardless of its dollar amount.

What the Denial Looks Like When the Deadline Is Missed

A timely filing denial arrives with a specific Medicare denial reason code CO-29 (Timely Filing) under the CARC code set, which communicates that the claim was not filed within the allowed time limit. The denial is issued by the Medicare Administrative Contractor processing the claim and applies to each line of service that falls outside the filing window.

When the denial arrives, it looks like any other denial in the queue. It has a reason code, a claim number, a payment amount of zero, and a date of determination. Nothing in its appearance signals that this denial is categorically different from every other denial the billing team is working. The distinction that matters that this denial has no remedy, while every other denial in the queue may have one is not communicated in the remittance. It is a billing knowledge issue: the team must know, when they see CO-29, that the account is closed.

The appropriate action when a CO-29 denial is received is to confirm the original date of service against the denial date, confirm that the twelve-month window has passed, document the write-off rationale in the account record, and write the balance off. Spending billing staff time attempting to appeal a CO-29 denial wastes resources on a process that will not succeed and delays attention to accounts that can still be recovered.

Are There Any Exceptions?

There are very limited exception categories that Medicare recognizes as grounds for accepting a claim outside the twelve-month timely filing window. These exceptions are narrow, require specific supporting documentation, and are reviewed by the MAC on a case-by-case basis. They include:

Administrative Error by Medicare

If the claim was submitted within the timely filing period but was rejected or lost due to an administrative error by Medicare or the MAC not by the facility the facility may submit the claim with documentation establishing that the original submission was timely and that the delay was caused by the Medicare system. This exception requires proof of the original timely submission, which is why maintaining claim submission records with timestamps is an operational necessity, not just a best practice.

Retroactive Eligibility

When a beneficiary’s Medicare coverage is retroactively established for example, when a Medicaid pending patient is later determined to have had Medicare coverage during the SNF stay the facility may file the Medicare claim within twelve months of the date the retroactive eligibility was established, rather than twelve months from the date of service. This exception requires documentation of the retroactive eligibility determination and the date it was received.

Disaster or Extraordinary Circumstances

CMS has authority to grant timely filing exceptions in geographic areas affected by declared disasters or extraordinary circumstances such as the national public health emergency provisions applied during the COVID-19 pandemic. These exceptions are granted systemically by CMS rather than applied for individually, and they apply only during the specified exception period to facilities in the affected area.

Outside of these specific categories, there is no mechanism for filing a claim after the twelve-month deadline and receiving Medicare payment. A sympathetic appeals process does not exist for timely filing. The deadline is absolute.

What this means for your facility: Do not spend billing staff time building appeal packets for CO-29 denials that do not meet one of these three narrow exception categories. Document the write-off, identify how the account reached the deadline without action, and correct the process that allowed it. The appeal will not succeed, and the time spent on it is time not spent on recoverable accounts.

The Billing Process Gaps That Allow Accounts to Reach the Deadline

Denied Claims Without a Rework Deadline

The most common path to a timely filing write-off is a denied claim that enters the rework queue without a documented deadline. The denial arrives, gets routed to the follow-up queue, and waits for the billing team to get to it. If the queue is managed by volume rather than by urgency working the newest denials while older ones wait accounts with earlier service dates quietly age toward the twelve-month mark without anyone tracking the original service date against the approaching deadline.

The process fix is a denial management workflow that assigns every denied claim a rework deadline based on the original date of service not the denial date and flags accounts within 90 days of the timely filing window for immediate escalation above all other work in the queue.

AR Aging Reports That Sort by Denial Date Rather Than Service Date

An AR aging report sorted by the date the account entered the AR system or the date the denial was received does not show the timely filing risk hiding in the account population. An account denied in month ten of a twelve-month service window looks like a recent denial. An account denied in month two but never worked looks like a two-month-old denial. Neither appearance reflects the timely filing reality, which is determined by the original service date.

Billing teams that rely on standard AR aging reports without a separate timely filing exposure view specifically showing open accounts sorted by original service date with days remaining in the filing window are managing AR without visibility into their most irreversible financial risk.

Staff Transitions That Orphan Accounts

When a billing specialist leaves voluntarily or through a vacancy the accounts they were actively managing may not transfer cleanly to a replacement. During the transition period, accounts that were in active rework may stop receiving attention. If any of those accounts have original service dates approaching the twelve-month window, the transition delay can be the difference between a recovered claim and a write-off.

Protecting against transition-related timely filing risk requires account ownership documentation that exists independently of the individual biller so that when the biller leaves, every account’s status, the rework steps in progress, and the timely filing deadline are visible to whoever takes over the file.

Medicaid Pending Accounts Without Timely Filing Coordination

When a resident is Medicaid pending applying for Medicaid at or after SNF admission the account may sit in a billing holding pattern while the eligibility determination is awaited. During that holding period, if the resident has Medicare eligibility that was not identified at admission, the Medicare timely filing clock may be running. When the Medicaid determination eventually reveals that Medicare coverage also existed, the Medicare filing window may have already passed.

Retroactive eligibility exception provisions can sometimes address this situation, but they require timely action when the eligibility determination is received, and they require documentation that supports the exception. Billing teams that discover retroactive Medicare eligibility late and fail to file immediately upon discovery frequently miss even the retroactive exception window.

Building a Timely Filing Protection Process

The facilities with the lowest timely filing write-off rates share one practice that protects them: they treat timely filing exposure as a daily operational metric, not a periodic AR review finding. Every open denied claim is evaluated against its original service date, not its place in the denial queue. A dedicated timely filing exposure report showing every open account within 180 days of its twelve-month window, sorted by days remaining is reviewed weekly and escalated immediately for any account within 60 days of the deadline.

Accounts within 60 days of the timely filing deadline should be the first accounts worked each billing cycle ahead of new submissions, ahead of recent denials, ahead of everything else. Revenue that can still be saved takes priority over revenue that cannot be lost yet.

How MCA Medical Billing Solutions Protects SNF Clients From Timely Filing Losses

MCA Medical Billing Solutions, L.L.C. maintains a timely filing exposure report for every client account tracking open denied claims against original service dates and escalating accounts within 60 days of the Medicare deadline as the top billing priority in every cycle. We do not manage AR by denial date. We manage it by service date, because that is the date that determines what can still be saved.

If your facility has experienced timely filing write-offs, contact MCA Medical Billing Solutions for a free billing assessment.