A commercial umbrella policy protects your company if underlying limits are exhausted.
For businesses, lawsuits can come from anywhere. An employee strikes a pedestrian with his car. A patron slips and falls, injuring himself while exiting your business. An advertisement lists the wrong phone number, causing thousands of annoying calls to an unrelated business.
Without sufficient general liability and commercial auto limits, you and your business are open to risk.
A commercial umbrella policy increases your liability protection if a lawsuit exhausts the limits of your current coverages.