Using this tab, you can specify the payment terms for the invoice received.
The "Invoice Received (create)" form. The Payment Terms tab
The Payment Terms field if filled automatically with the default terms defined for the supplier (for details, see Purchasing Payment Terms).
If you change the terms, the system will automatically recalculate pay dates and amounts for each payment installment if there are multiple stages in the payment process. You also can add installments and edit the installment amounts manually in the table. The sum of the installment amounts must be equal to the document total amount.