This study introduces and applies a new method for studying under-reporting of injuries. This method, “one-to-one injury matching”, involves locating and comparing individual incidents within company and insurer recording systems. Using this method gives a detailed measure of the difference in injuries recognised as “work-related” by the insurer, and injuries classified as “recordable” by the company. This includes differences in the volume of injuries, as well as in the nature of the injuries. Applying this method to an energy company shows that only 19% of injuries recognised by the insurer were recognised by the company as recordable incidents. The method also demonstrates where claiming behaviour and claims management have created systematic biases in the disposition of incidents. Such biases result in an inaccurate picture of the severity and nature of incidents, over-estimating strike injuries such as to the hand, and underestimating chronic and exertion injuries such as to the back.