If a student has the remaining amount in the previous session, then you can forward this remaining amount in the next session.
To carry forward fees, go to Fees Collection > Fees Carry Forward.
Here select Class, Section and then click on Search button.
The list of previous session balance fees will be shown in the below of the page and you can see Due Date present in right side of the page.
To set carry forward due date, go to System Settings > General Setting then go to Fees section and then enter Carry Forward Fees Due Days and then click on the Save button.
The number of days which you enter here due date will be exceed from current date.