Nearly all national insolvency laws contain rules which provide for the avoidance or nullification of legal acts which have been performed prior to the opening of insolvency proceedings. However, these transactions avoidance laws are quite diverse, not only in intensity but also in detail. This hampers cross-border business, insolvency proceedings, and restructuring significantly. It is for this reason that the European Commission strives for the harmonisation of this legal field in the EU. This book is the result of an intensive research project that digs-deep into this matter, comprising national reports from 24 jurisdictions and analysing the relevant topics from a principle-based perspective. The authors elaborate on the principles supporting and shaping transactions avoidance law, identifying the topics to be addressed from a principle-based perspective, and weighing and balancing the relevant principles to find adequate solutions for every single topic. The final result is a Model Law, comprising nine sections, which the authors recommend implementing into all national insolvency laws of the EU Member States in order to provide for legal certainty as to which transactions should (or should not) be challengeable in all Member States under the same conditions.