Michael Rush, B.Ec(Hons), LL.B(Hons) (Monash), BCL, M.Phil, D.Phil (Oxon), is a barrister and solicitor of the Supreme Court of Victoria and part time lecturer at the University of Melbourne.

The identity and existence of a loss-based defence in the law of unjust enrichment is disputed. Widely known as 'passing on', but better identified as 'disimpoverishment', this defence has generated confusion and disagreement across and within England, Australia, Canada and the United States of America. This book seeks to address these problems in three ways. First, by providing a solution to the defence's terminological problems and presenting a coherent picture of the current state of the law. Secondly, by examining whether a defendant's unjust enrichment can be said to have come 'at the expense of' a claimant when a third party has borne the cost of that enrichment. Put another way, whether awards of restitution are, or should be, restricted by the value of a claimant's loss. And finally, by analyzing the reasons in favour of accepting or rejecting a loss-based defence in the law of unjust enrichment. Numerous scholarly textbooks and law journals have devoted space to these issues. This work, however, has tended to focus narrowly on either particular cases or sets of issues. This book seeks to address this deficiency by collating, and providing total coverage of, the controversies and questions pertaining to a loss-based defence in the law of unjust enrichment.This work will be essential reading for anyone interested in the law of restitution, and in its relationship with other areas of private law.

1 Introduction
A. Thematic Outline
B. Chapter Summaries
Part I The Foundations
2 Introduction to the Defence of Disimpoverishment
A. Introduction
B. Questions in Unjust Enrichment
C. Definition
D. Change of Name
E. Another Problem with Pseudonyms
F. Triggering the Defence of Disimpoverishment
G. Assumptions
H. Taxation Agents
I. Burden of Proof
J. Judicial Responses to Disimpoverishment
K. Conclusion
3 Common Law Cases on the Defence of Disimpoverishment
A. Introduction
B. England
C. Australia
D. Canada
E. United States of America
F. Conclusion
4 Statutory Defence of Disimpoverishment
A. Introduction
B. The Defence of Unjust Enrichment
C. Operation of the Unjust Enrichment Defence
D. Recovery for Third Parties of Overpaid VAT
E. Influence of European Jurisprudence
F. Conclusion
Part II 'At The Expense Of' 5 What Might 'At the Expense of 'Mean?
A. Introduction
B. Two Interpretations of 'at the Expense of '
C. The Meaning of 'Loss'
D. Loss and Restitution
E. The Meaning of 'From'
F. Differences between 'From' and 'Loss'
G. Conclusion
H. Addendum
6 What do the Cases say 'At the Expense of 'Means?
A. Introduction
B. Situation 1: 'Gain' Exceeds 'Loss' at the Moment of Receipt
C. Situation 2: 'Gain' Increases After Receipt
D. Conclusion
7 What should 'at the Expense of 'Mean?
A. Introduction
B. The Problem Restated: The Status Quo Ante cannot be Restored
C. Four Conceptions of What 'At the Expense of 'Means
D. Whenever Loss and Gain Do Not Equate
E. 'Gain' Exceeds 'Loss'at the Moment of Receipt
F. 'Gain' Increases After Receipt
G. Conclusion
Part III Other Reasons to Reject or Accept the Defence of Disimpoverishment
8 Other Arguments for Accepting the Defence of Disimpoverishment
A. Introduction
B. False Bases for Accepting the Defence
C. A Legitimate Basis for Rejecting the Defence
D. Conclusion
9 Other Arguments for Rejecting the Defence of Disimpoverishment
A. Introduction
B. False Bases for Rejecting the Defence
C. Potential Bases for Rejecting the Defence
D. Three Reasons for Rejecting the Defence
E. Conclusion
Part IV Third Parties
10 Third Parties
A. Introduction
B. When Can an Action be Brought Against a Claimant?
C. Class Actions
D. Recovery of Overpaid Tax by a Third Party (from the Claimant)
E. Conclusion
11 Conclusion
A. The Problems Restated
B. The Conclusions Reached
C. Restatement