Invoice management System

Getting Server error while Creating Invoice management
Refer attached screen shots.
1]When we directly Click on Invoice details and Invoice summary it showing Java Script Error.
2]Getting Server on View Invoice
3]Getting Server error on when click on Show discrepancy when there no Source invoice value is available.

4]Getting Server Error there was already one Invoice we try to create new one.
5]Getting server error:Create Invoice page refer attached screen shots and follow below steps.
1]Create Invoice.Do not bill election Effective:On or after date:3/30/2016
2]Change Do not bill election Effective:On or after date as:2/30/2016
3]Click on Save button.
4]Getting Server error.

6]Getting Server error when deleting more than two invoice generated report at time. refer attached screen shots