entirely unpaid, the simple question is, whether the defendant shall be allowed to retain the money against the plaintiff, against whom he holds it manifestly without consideration, and compel the plaintiff to recover it by using the payment as a counter-claim or set-off against an innocent party, leaving that party to his remedy over against the defendant, or whether the defendant shall be compelled to pay it to the party to whom it will ultimately go, and from whom he received it without consideration. There was no interest to be paid, and the defendant did not apply it to the extinguishment pro tanto of the debt; and the plaintiff’s plea in an action brought against him on the bond would be, not payment, but a counter-claim or set-off.
Not only is the expense of plaintiff to be looked at from an equitable point of view, but in deciding whether the enrichment of the defendant is unjust, the question is to be approached in the same way. Hence, if the plaintiff has under mistake paid that which he could not have been compelled to pay either at law or in equity, but which is clearly a moral obligation, there is no unjust enrichment, and the plaintiff is not entitled to relief. “The rule has always been, that if a man has actually paid what the law would not have compelled him to pay, but what in equity and conscience he ought, he cannot recover it back again in an action for money had and received.”[1] Hence, if a party should, under mistake of fact as to the date when an obligation matured, pay a claim barred by the Statute of Limitations,he could not recover the money on the ground of mistake.[2] So where A, who purchased a promissory note from the payee before maturity, but by mistake failed to get an indorsement thereof, presented it for payment to the maker, and the maker, supposing that it was duly indorsed, paid it, it was held that he could not recover the money from A, notwithstanding the fact that the payee was largely indebted to him, and was insolvent. The Court said it was not against conscience for A to keep that to which but for a mistake he would have been entitled, both legally and equitably, which, however, owing to a technicality and accident, he could not have collected.[3]
Assuming that the mistake is of a kind recognized by the courts, and that the mistake has resulted in a failure of consideration to
