I've had this same issue come up as well. I got around it by logging into the customer's account with my master password. I'll then place the order online for the customer and redeem any coupons or points they have. This way, the order is in their online account, they'll receive an order confirmation, and they can take advantage of coupons or points. Any one-time use coupons are associated with the customer's account, and that person won't be able to use them online in the future.