​Legal Terms - Payment appropriation
Payment allocation refers to the process of assigning one or more payments to a specific obligation among multiple debts owing by a debtor to the same creditor. The user's text is concise.

The authority to allocate funds initially rests with the debtor, but if the debtor fails to allocate the funds at the time of payment, then the creditor has the right to do so. For current accounts, if there is no specific allocation, payments are typically assigned to the oldest unpaid debt.