The prepayment feature works fine ONLY IF you are manually processing a payment in QB from an estimate or sales order.  It is not working at all when the customer uses an Intuit payment link (send via QB payments).  When the payment makes its way to us we are prompted to apply the payment to the customer's account.  HOWEVER there is no option to use the incoming payment as a prepayment.  If an invoice is not being paid then the other choice is to keep the payment as a credit on the account.  Now how would I apply this credit to a sales order?  Or why can't Intuit fix the payment posting screen to allow the option to post as a prepayment against an order or estimate?  Waiting for a resolution to avoid serious financial errors caused by some prepayments handled correctly and others not.