For bill pay, the business wants recurring monthly payments: the customer picks a day of the month, and if that day falls on a weekend, the payment moves to the next business day. A customer picks the 31st. What questions would you ask the business, and how would you write the acceptance criteria?

账单支付要上线「每月固定日期自动付款」，业务方的原话是：客户选几号就在几号扣款，遇到周末就顺延。如果客户选的是 31 号，你会追问业务方哪些问题？验收标准你会怎么写？