實務上，供應商為了提高市場的競爭力，通常願意給予零售商一固定的信用交易期限，允許零售商在收到商品時，貨款可延至信用交易期限到期時才支付給供應商。零售商將信用交易期限內的銷售所得存入銀行帳戶，賺取利息；信用交易期限到期後，零售商將銀行帳戶內存款提出以支付貨款，若存款不足以支付貨款時，不足的部分則向銀行貸款支付。本研究主要針對損耗性物品探討在允許信用交易下的存貨模式。
本研究乃是以零售商的觀點，首先探討供應價小於零售價的存貨模式；再者針對Chung [8]的現金流量折現模式，提出更精確且簡單的演算法，以求得最佳訂購週期；最後，討論在有限倉儲容量下之存貨模式。本研究針對三個存貨模式，建立各存貨模式的目標函數，再根據各目標函數的特性，提出快速且精確的方法求解最佳訂購週期。

In practice, the supplier is willing to offer the retailer a certain credit period without interest during the trade credit period to promote market competition. Before the end of the trade credit period, the retailer can sell the goods and accumulate revenue and earn interest. A higher interest is changed if the payment is not settled by the end of the trade credit period. In this article, we propose some inventory models for deteriorating items under permissible delay in payment.
From the viewpoint of retailer, this article first considers the inventory model that the unit purchasing price is less than the unit selling price. Secondly, for the aim to overcome shortcoming of Chung [8], an algorithm is presented to locate the optimal cycle time and that is really very simple, accurate and rapid. Finally, we discuss the inventory model with limited storage capacity. We develop three models to determine the optimal cycle time and show the object functions that possess some properties. With those properties, the efficient solution procedures are presented to determine the optimal cycle time.

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