Unjust Enrichment Claims When a Contract Exists

To win on a claim for unjust enrichment, a plaintiff needs to demonstrate that (1) the defendant was enriched by the receipt of a benefit, (2) the enrichment was at the expense of the plaintiff and (3) that it would be unjust to allow the defendant to retain the benefit. Damon v. City of Kansas City, 419 S.W.3d 162, 192 (Mo. Ct. App. 2013). As an example, if someone pays off his neighbor’s mortgage, there may be a claim for unjust enrichment against the neighbor. The neighbor will have benefitted at the payor’s expense. The issue in that scenairio would be whether it would be “unjust” to allow the neighbor to retain the benefit. 
Unjust enrichment is not available in certain situations. If a plaintiff has entered into an express contract for the very subject matter for which he seeks recovery, unjust enrichment does not apply and the plaintiff’s rights are limited to the express terms of the contract. Howard v. Turnbull, 316 S.W.3d 431, 436 (Mo. Ct. App. 2010). To illustrate this point, assume an employee has a contract expressly setting forth his salary for a year. The employee could not sue the employer for unjust enrichment and claim that he has rendered benefits above and beyond the salary because he previously agreed to his salary and compensation in the contract. 
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