考虑一个销售多种可替代产品并提供相应免息消费信贷服务的公司，应用随机效用理论建立多项逻辑选择模型，并将消费者对免息信贷服务的反应纳入模型，分别在线性和非线性信贷服务成本结构下得到企业的最优免息期决策。研究发现，本质上可以将多产品最优问题转化成单一变量寻根问题，降低求解难度。有趣的是，消费信贷的最优免息期并不一定随着信贷服务成本的提升而缩减，也并不一定随着顾客对信贷服务偏好度的提升而增加。数值仿真表明，利润边际越大的产品，其对应的最优免息期也越长。为每个产品都提供专属的最优免息期方案整体利润均高于统一免息期方案，尤其是当企业的销售收入利用能力不强时，前一方案下的利润提升更加显著。

Consumer credit products have prevailed for a long time， allowing customers to spend first and pay later， stimulating customers to purchase products. Banks， financial service companies， and e-commerce platforms have all strategically laid out in this industry and provided corresponding online consumer credit services. To further stimulate consumption， companies will offer interest-free consumer credit services. We consider a firm that sells multiple substitutable products and provides interest-free consumer credit services and bears the service costs. We develop an MNL model and incorporate consumer responses to consumer credit services into the model， the firm’s objective is to make the optimal decisions of grace period for each product to maximize the total profit under linear and nonlinear credit service cost structures， respectively. The findings indicate that we can essentially transform the multiple products optimization problem into a single-variable root searching problem， which reduces the calculation complexity. The optimal grace period does not necessarily shrink with the increase of credit service cost and vice versa. Numerical analysis reveals that products with larger profit margins have longer optimal grace periods. We also compare the advantages and disadvantages of the two different credit options， namely， the uniform optimal grace periods for all products （Option 1） and the exclusive optimal grace period for each product （Option 2）. We find that the firm’s total profit from implementing Option 2 is always larger than that from implementing Option 1， especially when the firm’s ability to utilize the sales revenue is not strong， the profit improvement under Option 2 scheme is more significant.