退休公教人員存款優惠措施並非公教人員法定退休保障的一環，而係行政機關本於職權逕為實施之社會福利措施的一種，其實施雖無法律明文依據，但由於此等措施非屬法律保留之範圍，應非法所不許。退休公教人員優惠存款措施之提供與變動，均無涉公教人員法定退休保障。有權機關為推動退休公教人員優惠存款措施而訂定的各種辦法與要點，性質上並非源自法律授權的法規命令，而僅係行政規則，其規範對象主要是受託承辦優存業務之台灣銀行，並未授予退休公教人員任何權利主張之地位。承辦優存業務的台灣銀行，並非實施退休公教人員優惠存款措施的行政助手，亦非受委託行使公權力者。優存利息補貼機關與台灣銀行間應認為存有默示委託關係，為私法性質。退休公教人員與台灣銀行間應屬以私法契約所建立的私法上法律關係，所謂二階段理論，於此並無適用餘地。減核優惠存款金額函不具行政處分之性質，而僅是為日後存款契約之續約條件的預先通知性質。此外，本文認為行政規則不應納入人民得以主張信賴保護標的之範疇，而退休公教人員優惠存款措施之法律關係中，並不存有使存款人得以主張信賴保護之信賴基礎。

Preferential deposit for retired civil and teaching personnel is not a part of legal safeguard for civil and teaching personnel but a part of social welfare measures by administrative agencies based on their own legal authorities. The mere fact that such administrative practice is not authorized by legislation should not make it invalid because this practice involves no requirement for legal reservation. Furthermore, the offer and alteration of Preferential deposit for retired civil and teaching personnel have little relevance with the legal safeguard for retirement of civil and teaching personnel. In terms of the legal nature, the administrative regulations and guidelines regarding Preferential deposit for retired civil and teaching personnel instituted by authorities concerned are not legal orders based on the authorization by legislation; instead, they are simply administrative rules. The regulated subject of these correlative regulations is primarily the Bank of Taiwan that undertakes preferential deposit affairs, and these correlative regulations did not grant retired civil and teaching personnel any legal standing. Bank of Taiwan is neither an administrative auxiliary nor is it an entity commissioned to exercise public authority. Between the administrative agencies that offer the interests subvention and the Bank of Taiwan exists an implied mandatory relationship of a private law nature. The relationship between retired civil and teaching personnel (depositor) and the Bank of Taiwan is also in a private law nature that is established by private law contract; therefore, the so-called ”two-stage-theory” is not applicable here. The letter on reducing preferential deposits amount is not an administrative act but merely a notice of terms of future contract renewal. In addition, this article contends that administrative rules should not be the basis for reliance protection claims. As for the legal relationship concerning measures of preferential deposits for retired civil and teaching personnel, there is no reliance basis for the depositor to claim the reliance protection.