Final answer:
If Medicare denies a claim, the appellant has 120 days from the date of notice to file an appeal. The appellant must act promptly within this period to present their case with the necessary documentation.
Step-by-step explanation:
When Medicare has denied a claim, the appellant has 120 days from the date of the Medicare Summary Notice (MSN) or Explanation of Benefits (EOB) to file an appeal. This 120-day period is known as the filing window for the appeal process at the first level of appeal, which is the redetermination by a Medicare Administrative Contractor (MAC). If the appellant misses this deadline, the opportunity to appeal may be lost unless there are exceptional circumstances that warrant a late filing. It is important for the appellant to act promptly and make sure that all necessary documentation is in order to support their case for an appeal within this timeframe.