»Opting Out of The Application of UN Sales Law Due to Legal Uncertainty«: In practice, parties still regularly - consciously or unconsciously - opt out from the application of UN Sales Law. One of the most common reasons given is an allegedly too high degree of legal uncertainty when applying UN Sales Law. The author examines the extent to which the deselection of UN Sales Law on the basis of alleged legal uncertainty is convincing. It is shown that the blanket accusation of too much legal uncertainty when applying UN Sales Law can no longer be upheld. The focus of the study lies, among other things, on an in-depth assessment and presentation of the abundance of working materials and German as well as international case law on UN Sales Law. Furthermore, a detailed analysis of the existing international literature and case law is undertaken in order to demonstrate the great degree of legal certainty with which both the scope of application of UN Sales Law can be determined and central (exemplarily selected) substantive legal questions can be answered.