Restitution & Unjust Enrichment in English Law: Key Principles, Claims and Remedies

Unjust enrichment is a powerful yet often underused legal remedy that allows a claimant to reverse a defendant’s gain that has come at the claimant’s expense in circumstances the law considers unjust. Unlike claims in contract or tort, restitution focuses not on loss suffered but, on the benefit wrongfully received. The remedy aims to strip the enrichment, returning it to the rightful party.

At LEXLAW, our solicitors and barristers regularly act for clients in high-value commercial, financial, and contractual disputes where unjust enrichment claims play a central role. This guide explores how these claims arise in practice, the applicable legal tests, and the kinds of real-world scenarios where claimants can successfully secure restitution including situations that are frequently overlooked by mainstream guidance.

For tailored advice, see how our Banking Litigation or Commercial Disputes teams can help you take immediate legal action.

What Is Unjust Enrichment?

In the jurisdiction of England & Wales, unjust enrichment has developed into a standalone cause of action. The core principle is simple: no one should retain a benefit that was transferred to them without a legal basis.

The House of Lords formally recognised unjust enrichment as part of English law in Lipkin Gorman v Karpnale Ltd [1991], holding that a recipient of misappropriated funds even if unaware of the wrongdoing could be ordered to make restitution. Since then, the law has evolved through landmark cases such as Banque Financière de la Cité v Parc (Battersea) Ltd

The courts follow a well-established four-part framework when assessing claims:

1. The defendant has been enriched;
2. The enrichment occurred at the claimant’s expense;
3. The enrichment was unjust; and
4. No applicable defence bars the claim.

Each of these elements must be established with evidence. If successful, the court can award restitution, often in the form of repayment, asset recovery, or even disgorgement of profits.

When Can You Bring a Claim for Unjust Enrichment?

Unjust enrichment commonly arises in banking errors, mistaken payments, frustrated contracts, or unauthorised use of client funds. However, its reach extends far beyond these categories.

Take, for example, a business that accidentally pays a supplier twice for the same invoice. If the supplier refuses to return the duplicated payment, claiming it as a performance bonus, the paying party may have a valid restitution claim.

Another example is where a bank holds on to a cutomer’s funds without legal justification delaying transfers under vague “compliance reviews” while using the client’s capital to generate profits this could also give rise to a claim in unjust enrichment, in addition to breach of contract.

In these situations, LEXLAW’s legal team can swiftly assess whether restitution is appropriate and begin steps to recover your funds, even where litigation is necessary.

Case Study Applications: How Unjust Enrichment Claims Work in Practice

Our specialist solicitors frequently advise in high-value disputes involving restitution and unjust enrichment. The following real-world cases demonstrate how the legal principles operate across sectors from banking and insurance to commercial fraud.

1. Mistaken Insurance or Invoice Payments

Based on Kelly v Solari: an insurance underwriter mistakenly pays out a claim to a former policyholder whose coverage had lapsed. After internal audit, the mistake is identified, but the recipient refuses to return the funds, arguing they had believed the payout was legitimate.

Legal Position:
This situation reflects the principle from Kelly v Solari that even innocent recipients must return funds paid under a causative mistake of fact or law. Restitution is available if the payer would not have made the payment had they known the true position. The same principle applies in modern contexts, such as overpayments of invoices or duplicate bank transfers. Our firm regularly secures full recovery for clients by proving the mistaken basis of payment.

2. Receipt of Stolen or Misappropriated Funds

Based on Lipkin Gorman v Karpnale Ltd: A law firm discovers that a former partner embezzled client monies and spent them gambling at a casino. The firm seeks restitution of the lost funds directly from the casino, even though the establishment accepted the money in good faith.

Legal Position:
The House of Lords confirmed that unjust enrichment can apply even where the recipient is innocent, so long as there’s no legal basis for retention. The case clarified that enrichment is unjust where funds are received as a result of a breach of trust or unauthorised transaction. We have pursued similar claims against financial intermediaries, crypto exchanges, and online platforms who unwittingly receive the proceeds of fraud.

3. Void Contracts Due to Legal Incapacity

Based on Westdeutsche Landesbank v Islington LBC: a local authority enters into a complex interest rate swap arrangement with a European bank. Years later, the transaction is declared void because the authority lacked the legal capacity to enter into such contracts.

Legal Position:
This case confirms that money paid under a contract later found to be ultra vires (beyond legal powers) is recoverable in restitution. The key unjust factor is “incapacity.” We apply this principle in disputes involving government bodies, charities, or companies acting beyond their constitutional limits. Restitution ensures recovery even in the absence of wrongdoing, where legal foundations are missing.

What Remedies Are Available For Unjust Enrichment?

The most common remedy is personal restitution: an order requiring the return of funds or equivalent value. In some cases, where the benefit can be specifically traced into a particular asset or account, proprietary restitution may be available, granting claimants rights over specific property.

In finance-related cases, the courts may also award compound interest where the defendant derived measurable benefit from use of the funds as affirmed in Sempra Metals Ltd v HMRC. If the enrichment is accompanied by wrongdoing, claimants may also pursue account of profits or equitable compensation.

If you’re unsure whether restitution or damages are appropriate in your case, LEXLAW’s commercial litigation team can provide strategic analysis and practical next steps advice.

What are the Legal Defences to an Unjust Enrichment Claim?

While a claim may appear straightforward, defendants can rely on several defences. These include:

• Change of position: Arguing that the benefit was spent or used in good faith and cannot be returned without hardship.
• Estoppel: Claimant’s conduct induced reliance.
• Limitation: Most claims must be brought within six years.
• Bona fide purchase: Where the benefit was acquired in good faith with value and without notice.

In our experience, delay in taking action can significantly weaken a restitution claim, particularly if the defendant has altered their position over time. We therefore recommend that clients seek legal advice immediately upon discovering the issue.

Instruct Specialist Unjust Enrichment Claim Lawyers

Restitution for unjust enrichment is increasingly deployed in litigation involving banks, investors, developers, and corporate clients. Whether your funds were wrongly withheld, your services went unpaid under a void contract, or someone else profited from your loss unjust enrichment may be the legal route to strip the benefit and recover what is rightfully yours.

At LEXLAW Solicitors, we specialise in acting on complex restitution claims particularly where financial, contractual, or regulatory elements are involved. We have represented clients in multi-million-pound disputes including claims against major banks, crypto platforms, and public authorities.

If you believe another party has retained a benefit they are not legally entitled to, speak to our specialist unjust enrichment lawyers today.