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 New Hampshire, the doctrine of unjust enrichment is recognized by the courts as a means to ensure fairness in situations where no formal contract exists between parties. This legal principle allows a party to seek restitution if they have conferred a benefit on another party under circumstances that would make it unjust for the recipient to retain that benefit without providing compensation. The courts in New Hampshire look at the specifics of each case to determine whether an implied or quasi-contractual obligation exists, based on principles of equity and good conscience. The doctrine is not based on the presence of wrongdoing but rather on the equitable concept that the person who has been unjustly enriched at the expense of another should make restitution. The key consideration is where, in equity, justice, and law, the money or benefit rightfully belongs, and the aim is to prevent an unconscionable loss to the person who provided the benefit and to avoid allowing the recipient to be unjustly enriched.