noun
corresponding amount; equivalent sum
Used in financial or accounting contexts to refer to an amount that matches or corresponds to another amount, such as a payment matching an invoice or a fund matching a liability.
請求書の対当額を確認してから支払いを行ってください。
Please confirm the corresponding amount on the invoice before making the payment.
この基金は将来の債務に対する対当額として積み立てられている。
This fund is set aside as an equivalent sum for future obligations.
同額 means 'the same amount' in a strict numerical sense, whereas 対当額 implies a corresponding or balancing amount that may not be identical but is matched in purpose.
Compound of 対当 (matching, corresponding) and 額 (amount). The exact historical derivation is uncertain, but the term is used in modern financial and legal contexts.