Financial Settings / General Settings / e-Payments / Basic Settings / Default payment amount on every online payment
Here you define whether in online payments you can freely choose the amount according to the instalments, whether all instalments or overdue instalments have to be paid.
Example in parent’s portal
Setting -> All installments
All installments are preselected and the total amount is locked
Setting -> Payment in advance
The total amount is zero, a parent can click on + and add specific amounts