Once the Supplier window is displayed and is the active window, the Supplier shortcuts are displayed on the Shortcut bar. Select Payment to display the Supplier Payment window:
On the Supplier Payment window, click the Prepayment button.
A message box with information appears. You have the option to continue or abort the prepayment transaction.
Enter the amount you wish to pay and press <ENTER> to confirm.
then save the prepayment.
After you click Save a message is displayed reminding you that this unallocated amount can be linked to current or future invoices:
then you are returned to the Supplier window. If you click on the Transactions tab you will see that the payment has been recorded but is not allocated to any invoices.
For details of the linking procedure please see Unallocated Payments and Linking