Supplier payment order with payment on account

Hi, Ines

I think problem is in sign of amounts. It was explained somewhere already on this group. 
You can create proposal with supplier payment of accounts. You can create payment order which will include payment on account. But only together with other documents (invoices…) of same supplier -  to make payment amount positive. In case of payment TO supplier, total amount of payment must be positive - creating payment order, you are instructing your bank to send some money from your account to a supplier account. Payment with negative amount means opposite case - instructing bank to withdraw some money from supplier bank account and transfer it to your account - and it requires different process, like direct debit. 

You may check this thread as well: