Unlike the other causes of action in this rubric, such as tortious interference or unfair competition, unjust enrichment is not inherently an intentional tort; to the contrary, New York's courts have held that it requires only a showing of the following:
"1) that the defendant benefitted;
2) at the plaintiff's expense; and,
3) that equity and good conscience require restitution."
Kaye v. Grossman, 202 F.3d 611, 616 (2d Cir. 2000) (citation omitted).
As another New York court put it, To state a cause of action for unjust enrichment, a plaintiff must allege that it conferred a benefit upon the defendant, and that the defendant will obtain such benefit without adequately compensating plaintiff therefor.” Nakamura v. Fuji, 253 A.D.2d 387, 390 (1st Dept. 1998).
Importantly, the doctrine of unjust enrichment is available whether the defendant has obtained the money by wrongdoing, illegality, or mere mistake. See, e.g., Parsa v. State of New York, 474 N.E.2d 235, 237-38 (N.Y. 1984). In fact, a cause of action may lie even if the defendant did not intend to injure the plaintiff. See, e.g., Corsello v. Verizon N.Y. Inc., 2012 WL 1032741 (N.Y. 2012) ("Typical [unjust enrichment] cases are those in which the defendant, though guilty of no wrongdoing, has received money to which he or she is not entitled").
A word of caution is in order here.
An unjust enrichment claim will lie only where there is no enforceable contract. Stated differently, you cannot have a valid claim for both breach of contract and unjust enrichment concurrently. If both claims are made, the court is obliged to dismiss either one or the other.