"I added everything to my cart to start the checkout process and the $20 deposit we made [on-site] is not applying?"

I'm getting emails like this a lot. People are prompted to apply the deposit on file when they click next, but instead of doing that they're emailing, which is much harder. This I think illustrates that the end user really expects for a deposit to be showing in My Cart itself.

My suggestion is to put the ~do you want to use deposit on file inside the My Cart itself to clear this up and save a click through screen to get to credit card entry in one less step.

Alternatively, just add an option for IBY that if a customer has a deposit on file, automatically apply that deposit and show it in My Cart.