To carry forward fees, go to Fees Collection > Fees Carry Forward. If a student has the remaining amount in the previous session, then you can forward this remaining amount in the next session. 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. Here you can see Due Date present in right side of the page.

Fees carry forward image

To set carry forward due date, go to System Settings > General Setting then  go to Miscellaneous 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.