Yes. A disability insurance claim is not like an automobile accident claim, where you may have years after the incident to file a lawsuit. Under ERISA rules and regulations, you only have 180 days from the date on the insurance company’s denial letter to file your appeal. It is critical that you give notice of your appeal before this deadline.
Note: Some long-term disability policies provide for a second level appeal, and the deadline is often shorter than 180 days.