Hello Angela,
One way of pre-paying the supplier is by asking supplier to raise an invoice for it. The AP department will get this invoice and the invoice will have all receiving related exceptions since nothing would have been dleivered by then. AP department can then process the invoice and make a payment to the supplier.
I believe this process is not the best industry practice to make the pre-payments. But this is the workaround until we build the complete functionality.
If you want to talk about this more, please do email me at dsanghi@ariba.com.
Regards,
Deepak Sanghi
Director, Product Management, Ariba.