A person having several debts of the same kind in favor of a single creditor may declare, at the time of making a payment, to which of them it is to be applied.\nIf the debtor should accept a receipt from the creditor, setting forth the application of the payment, he cannot make a claim against it, unless there should be some cause which may invalidate the contract.\nHistory —Civil Code, 1930, § 1126.
Puerto Rico Legal Code