Change of position is a defence to a claim in unjust enrichment

Unjust enrichment

Unjust enrichment is a legal term denoting a particular type of causative event in which one party is unjustly enriched at the expense of another, and an obligation to make restitution arises, regardless of liability for wrongdoing.Definition:...

, or for restitution

Restitution

The law of restitution is the law of gains-based recovery. It is to be contrasted with the law of compensation, which is the law of loss-based recovery. Obligations to make restitution and obligations to pay compensation are each a type of legal response to events in the real world. When a court...

. Ordinarily, someone who has been unjustly enriched at the expense of another is strictly liable

Strict liability

In law, strict liability is a standard for liability which may exist in either a criminal or civil context. A rule specifying strict liability makes a person legally responsible for the damage and loss caused by his or her acts and omissions regardless of culpability...

 to disgorge his gains. However, a "change of position" defence operates where it would be inequitable to compel him to make restitution.

In English law, explicit recognition of the defence in response to an unjust enrichment claim was only first made in Lipkin Gorman v Karpnale Ltd

Lipkin Gorman v Karpnale Ltd

Lipkin Gorman v Karpnale Ltd [1991] 2 AC 548 is a foundational English unjust enrichment case. The House of Lords unanimously established that the basis of an action for money had and received is the principle of unjust enrichment, and that an award of restitution is subject to a defence of change...

[1991] 2 AC 548.

Cases

• Ministry of Health v Simpson [1951] AC 251, affirming Re Diplock [1948] Ch 465