One calendar year. CMS says to "File Medicare claims with your MAC no later than 1 CY after the date of service," and the regulation, 42 CFR 424.44(a)(1), says the claim must be filed "no later than the close of the period ending 1 calendar year after the date of service." If a claim misses that deadline, CMS: "You can't appeal a determination that a claim wasn't filed on time."
Scope: this is Medicare fee-for-service. Other payers set their own filing limits, so check your payer contracts.
The rule, in CMS's words
From CMS's MLN booklet on CMS-1500 and 837P billing (MLN006976, Dec 2025):
CMS: "File Medicare claims with your MAC no later than 1 CY after the date of service."
"CY" means calendar year. The regulation says the same thing in its own words:
42 CFR 424.44(a)(1): the claim must be filed "no later than the close of the period ending 1 calendar year after the date of service."
When the clock starts
In general, the start date is set by the claim itself, not by when someone gets around to working it:
CMS: "In general, the start date for determining the 1 CY timely filing period is the date of service or From and Through date on the claim."
What happens after the deadline
Know this before a claim gets close to the line. CMS is direct:
CMS: "We deny claims filed after the deadline. When a claim is denied for timely filing, it's not the same thing as an initial determination. You can't appeal a determination that a claim wasn't filed on time."
In other words, a timely-filing denial doesn't open an appeal path. CMS says it isn't an initial determination, and that it can't be appealed.
Exceptions exist, and CMS points to the manual
CMS: "There are limited exceptions to the 1 CY timely filing deadline. For more information, see Medicare Claims Processing Manual, Chapter 1, section 70."
This page deliberately doesn't list or summarize those exceptions. For the details, go to the manual section CMS names.
A habit that helps
An operational suggestion, not a CMS rule: run a weekly aging view that flags claims getting close to the one-year mark before they reach it. That way you see which claims are nearing the deadline while there's still time to file them.
Scope: Medicare fee-for-service only
Everything above is Medicare fee-for-service. Other payers set their own filing limits, so check your payer contracts.
FAQ
What is the Medicare timely filing limit?
CMS: "File Medicare claims with your MAC no later than 1 CY after the date of service." 42 CFR 424.44(a)(1) says the claim must be filed "no later than the close of the period ending 1 calendar year after the date of service."
When does the Medicare timely filing period start?
CMS: "In general, the start date for determining the 1 CY timely filing period is the date of service or From and Through date on the claim."
Can I appeal a Medicare timely filing denial?
CMS: "You can't appeal a determination that a claim wasn't filed on time." CMS also says that when a claim is denied for timely filing, "it's not the same thing as an initial determination."
Are there exceptions to the 1 calendar year deadline?
CMS: "There are limited exceptions to the 1 CY timely filing deadline. For more information, see Medicare Claims Processing Manual, Chapter 1, section 70."
Related resources
- How to start with one focused aging A/R project
- How to define a denial queue before asking for outside help
Know what's moving, what's stuck, what happens next. Start with one queue.
This page is run by RxRev.
Sources: - CMS, MLN006976, Medicare Billing: CMS-1500 & 837P (Dec 2025), "Time Limits for Filing Claims," p. 9 - 42 CFR 424.44, Time limits for filing claims (via Cornell LII)