This error usually occur when Fee Setting Done Then changes in Class Fee Structure in the mid-Session.

NOTE:   After Fee Setting done don’t changes in “Class Fee Structure” 

Solution- Go to Student Module. Select Modify section. Select Shift, Class and click on    Load Record. Select Student and click on Edit button. Click on Class Change (Not Recommended) option. Then click on Yes Button. Then Click on Update button. Then again do Fee Setting.

NOTE:   Make sure if you click Yes button then your following Data are Deleted from current Session. (Student Fee Detail, Student Exam Detail and Transport Detail )