Difference between partial and residual payment
In the case of Partial payment, SAP system will keep all the partial payments and the invoices as OPEN- however they are linked through a field called “Invoice Reference”. By sorting on invoice referencing you will know at any point of time all the payments, invoices and other line items against that invoice references.
If you do the partial payment through “Residual payment” tab, SAP system will CLEAR the original invoice for the full amount and it creates a new line item for the remaining amount yet to be paid. It is the open item.