What is a "double tapped" circuit breaker?

A double tapped circuit breaker, commonly referred to as a “double tap” is an electrical defect inside an electrical panel. 

Double taps are only visible when the panel cover is removed and is the most common electric panel defect that we find at Pro-Elements Home Inspection. Double taps are a fire hazard, and therefore should be addressed as a homeowner becomes aware of them.

A double tap occurs when two wires are connected to a single circuit breaker that is only engineered to accept one wire (see photo below). 

This is a defect because two wires in a single breaker may not be properly tightened to the breaker and loose wires have the potential to cause overheating and arcing.