What is the Medicare timely filing limit?

An Original Medicare Part A or Part B claim must be filed no later than 12 months, or 1 calendar year, after the date of service (42 CFR 424.44).

When does the Medicare timely filing clock start and stop?

It starts on the date of service, which is generally the From date on the claim. For an institutional claim with span dates it is the Through date, and for a professional claim with span dates it is the line item From date. It stops on the date the appropriate Medicare contractor receives the claim.

Can you appeal a Medicare timely filing denial?

No. A determination that a claim was not filed timely is not an initial determination, so it is not subject to appeal (42 CFR 405.926(n)). If one of the exceptions in 42 CFR 424.44(b) applies, you ask the Medicare contractor for an extension of the filing time and send the documentation for it.

What are the exceptions to the Medicare timely filing limit?

There are four: administrative error by Medicare or its contractor, retroactive Medicare entitlement, retroactive Medicare entitlement where a State Medicaid agency recovered its payment 6 months or more after the service, and retroactive disenrollment from a Medicare Advantage plan or PACE organization where the plan recovered its payment 6 months or more after the service.

What is the timely filing limit for commercial payers and Medicare Advantage plans?

Each one sets its own limit in its contract. Check your payer contract first, then the payer's provider manual. The Medicare rule on this page does not apply to them.

Medicare timely filing limit: 12 months from the date of service

Q: Which denial code does Medicare use for timely filing?

CMS instructs its contractors to deny a late claim with reason code 29, the time limit for filing has expired, and remark code N211, you may not appeal this decision.

The facts in one place

Limit	1 calendar year (12 months) after the date of service. 42 CFR 424.44(a).
Clock starts	The date of service, generally the From date on the claim.
Clock stops	The date the appropriate Medicare contractor receives the claim.
Last day on a weekend	If the last day is a Saturday, Sunday, legal holiday, or other federal nonworkday, the deadline moves to the next workday. 42 CFR 424.44(c).
Denial	Reason code 29 with remark code N211. On the remit this reads CO 29.
Appeal	None. The denial is not an initial determination. 42 CFR 405.926(n).
Exceptions	Four, in 42 CFR 424.44(b). Each extends the time through the last day of the 6th calendar month after the triggering event.

This covers Original Medicare fee-for-service claims. A Medicare Advantage plan or a commercial payer sets its own filing limit in its contract. Check your payer contract, then the payer's provider manual. We do not print their numbers here, because the contract you signed is the only one that counts.

How the 12 months are counted

The rule is in the Medicare Claims Processing Manual, Chapter 1, section 70. Which date starts the clock depends on the claim type:

A claim with one date of service: that date, the From date.
An institutional claim with span dates (UB-04, 837I): the Through date.
A professional claim with span dates (CMS-1500, 837P, including DME supplies and rentals): the From date of each line item. If a line's From date is late but its To date is not, the contractor splits the line and denies the late part.
A date of service on February 29: the claim must be filed by February 28 of the following year.

For example, a service on March 10, 2026 must be received by March 10, 2027. The clock stops on the receipt date the Medicare contractor gives the claim, not on the date you sent it.

A submission that came back is not a filed claim. A claim returned to the provider (RTP) as incomplete or invalid is not a claim for timely filing, and neither is one sent to the wrong Medicare contractor until the right one receives it. The clock keeps running in both cases. Fix and resubmit early, not in month 11.

What a late claim looks like on the remit

CMS tells its contractors to deny a claim received after the time limit with reason code 29 (the time limit for filing has expired) and remark code N211 (you may not appeal this decision). See CMS Transmittal 830. Our page on CO 29 covers the code itself.

The provider carries the loss. Where the provider was responsible for the late claim, it may not charge the beneficiary for the service, except the deductible and coinsurance that would have applied if Medicare had paid.

Can you appeal a timely filing denial?

No. Under 42 CFR 405.926(n), a determination that a provider or supplier failed to submit a claim timely is not an initial determination and is not appealable. The manual says the same in section 70.4. A redetermination request is the wrong tool here.

What you can do is show that an exception applies. The exceptions are not an appeal. You ask the Medicare contractor to extend the filing time, and you send the documentation it needs to decide. If you file a late claim with no explanation attached, the contractor assumes you accept responsibility for the late filing.

The four exceptions

From 42 CFR 424.44(b) and manual section 70.7. Each one extends the filing time through the last day of the 6th calendar month after the month of the triggering event.

Administrative error. An employee, contractor, or agent of Medicare caused the late filing through error or misrepresentation, for example wrong coverage information or an excessive delay in information you needed to file. The time runs from the month you were notified that the error was corrected. Send a statement of how you learned of the error and when it was corrected, with a written report, letter, or statement from Medicare or its contractor that shows the error. The contractor does not accept these requests more than 4 years after the date of service.
Retroactive Medicare entitlement. The patient was not entitled to Medicare on the date of service and was later notified of entitlement effective on or before that date. The time runs from the month of that notice. Send the official Social Security Administration letter with the entitlement date, and the services and dates of service.
Retroactive entitlement with a Medicaid recovery. As above, and the State Medicaid agency recovered its payment from you 6 months or more after the date of service. The time runs from the month of the recovery. Send proof of the recovery date, of the retroactive entitlement, and of the services.
Retroactive disenrollment from Medicare Advantage or PACE. The patient was enrolled in a Medicare Advantage plan or a PACE organization, was later disenrolled effective on or before the date of service, and the plan recovered its payment from you 6 months or more after the date of service. The time runs from the month of the recovery. Send proof of the prior enrollment, the disenrollment notice and its effective date, and the plan's recovery.

Two traps near the deadline

You cannot add a service after the limit. If a service was left off the original claim, an adjustment to add it is not allowed once the filing time for the original claim has expired.
A correction to a timely claim is different. An adjustment that corrects information on a claim that was filed on time follows the reopening rules, not the filing limit.

Sources

42 CFR 424.44, Time limits for filing claims, eCFR
Medicare Claims Processing Manual, Pub. 100-04, Chapter 1, section 70, CMS.gov
42 CFR 405.926, Actions that are not initial determinations, eCFR
Transmittal 830, Change Request 4041, Denial of Claims Not Timely Filed, CMS, February 2006

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