The doctrine of unjust enrichment applies the principles of restitution to disputes that are not governed by a contract between the parties. It characterizes the result of a failure to make restitution under circumstances that give rise to an implied or quasi-contractual obligation to return those benefits.

The courts describe this claim in general principles. For example, courts have stated that a claim for unjust enrichment seeks to restore money where equity and good conscience require restitution; it is not premised on wrongdoing, but seeks to determine to which party, in equity, justice, and law, the money belongs; and it seeks to prevent unconscionable loss to the payor and unjust enrichment to the payee.

Because recovery based on unjust enrichment of another party relies on the court's sense of fairness or equity rather than the law, it is often referred to as the equitable doctrine of unjust enrichment.

In Pennsylvania, the doctrine of unjust enrichment is a legal principle that allows a party to seek restitution when there is no enforceable contract between the parties, but one party has received a benefit at the expense of another. This doctrine is based on equity, meaning it is grounded in principles of fairness rather than strict legal rules. Pennsylvania courts will consider an unjust enrichment claim when one party has been enriched and it would be inequitable for them to retain that benefit without compensating the other party. The key elements that must be proven for a claim of unjust enrichment in Pennsylvania are: (1) benefits conferred on the defendant by the plaintiff, (2) appreciation of such benefits by the defendant, and (3) acceptance and retention of these benefits under such circumstances that it would be inequitable for the defendant to retain the benefit without payment of value. The goal of this doctrine is to prevent one party from being unjustly enriched at the expense of another, ensuring that the party who provided the benefit is fairly compensated.