履約保證金，乃承攬工程之承包商於得標後，須提供業主之保證金，以擔保契約之履行。承包商為避免承攬工程時，須提出鉅額現金作為履約保證金，影響資金之流通，故以銀行開具履約保證書以代替現金給付。履約保證書是為給付保證金之代替，具有現金支付功能。針對此一獨特性之特徵，自有將其契約歸類加以定性之必要。
履約保證書之功能除擔保業主之債權獲得清償外，業主依銀行所出具之保證書上之記載立即照付約款而為請求，銀行之付款為直接之主要義務，業主可以迅速而確定地自銀行獲得付款，銀行依該保證書直接對業主負責。此種擔保模式業主居於相對優勢之法律地位，但另一方面，業主卻也有權利濫用之可能。如就業主、承包商、銀行三方當事人之利益衡量，實有詳予研究探討之必要。
我國實務上對於履約保證書之法律性質見解分歧，保證契約附立即照付約款是德國法特有的制度，本文擬藉助德國法上實務及學說，對保證契約附立即照付約款所生法律問題之研究進行說明，並整理我國近年之實務見解，而提供不同比較法視野，以供參酌。

Performance security deposit, is the hiree after the winning bid shall provide hire the bond to guarantee the performance of the contract. Instead of cash payment, the performance bond issued by the bank is used by the hiree to avoid a lump sum of cash requirement in the construction contract that can have impact to the fund flow. The performance bond acts as an alternative security deposit with a cash payment function, with such unique characteristics, it is important to classify its own nature.
Except secured claim by hire, the function of performance bond is immediately and certainly payment to hire from the bank that based on the first demand requested from the hire according to the performance bond which issued by the bank. The direct principal obligation for the bank is payment, and the bank has direct responsibility to the hire in line with the performance bond. The hire has comparative advantage in the legal status under such security form, but on the other hand, there is possibility fraudulent gain by the beneficiary (or abuse of right). Therefore, it is important to explore the interest balance among hire, hiree, and the bank.
In Taiwan, courts have controversies over the legal nature of the construction performance bond containing a statement of immediate payment. The first demand guarantee is unique to German law. Therefore, this article compared focus on the German legal practice and theory on the first demand guarantee and analyzes recent years court decisions in Taiwan.