In legal cases seeking damages, it's essential to show that harm was caused to the person making the claim due to unlawful actions by the defendant. The chapter delves into how this harm suffered by the claimant is measured or quantified. A tricky issue often faced is the concept of pass-on, especially in competition law damages claims, which has been handled differently in the US compared to the EU. This aspect is crucial as it plays a significant role in shaping policies related to these claims. Additionally, the chapter touches on the topic of indirect purchaser standing, which is treated differently in the EU compared to the US, where a more straightforward approach is taken.