The bonus is supposed to be applied to the following bill. I took a screenshot of the conversation with support, so that I have proof if something goes wrong. I'm not sure if that will go to the very next bill or the bill after the phone arrives. 

So when do you actually see the bonus? A follow-up email? 

I've seen some confusion in different places as to whether the $50 pre-order bonus was being granted *until* today or *through* today. I just got off a chat with Fi customer service, because I saw no mention of it during my trade-in and order. Customer service confirmed that you have until midnight to get the credit, so I thought some people would like clarification. 

Confirmed Moto X4 $50 pre-order bonus through midnight.