at-once payment

基本解释

Finally, guests can check-out from their mobile device at any time, even once they have left the property, settling outstanding charges via secure payment systems.
最后，客户可以在任何时候通过手机结账，甚至在他们离开酒店之后，他们也可以通过安全的支付系统来结算一些未支付的费用。
Make sure you have a payment schedule in place and make sure your clients understand when you expect to get paid. It could be once a month, up-front, upon completion or at a different set interval.
确定你有一份付款进程表并确定你的客户知道你希望什么时候付款.可以是一月一付,可以是完工后付,也可以是某个间隔时间付.