Unique in its breadth, this book undertakes a comparative analysis of the ways in which legal systems in all regions of the world deal with agreed sums payable upon breach of an obligation. The book shows divergences and convergences and indicates trends as to the future development of the law. It also deals with the treatment of agreed sums under the 1980 UN Convention on Contracts for the International Sale of Goods (CISG), offering the first comprehensive solution to this issue based on comparative analysis. For practitioners as well as researchers, this book is a valuable source of information and offers suggestions for solutions to current and future issues.