This varies by insurance company. Each one is different but common periods are 90, 120, 180, and 365 days. If the insurance company does not receive your claim within their period it will be denied and you will be responsible for all charges. This has nothing to do with any other denial reason and very difficult to override.
The Website below has the timely filing period for many popular insurance plan.
Remember to confirm that your claim was sent.
Contact the insurance company within 7-10 days to confirm they received it.
You should get an Explanation of Benefits (EOB) within 30-60 days.
Do not allow Timely Filing Period to Expire.
Note that if you appeal a denied claim the clock starts again. Multiple appeals can take many months and even a year or more.
An updated Reimbursement Checklist is below. If you follow it meticulously you should be reimbursed.