How to customize the Balance Sheet Report
This is an example of a Query Report that requires sql query changes.
This may help explain Custom query report
The Balance Sheet report is a very complex report, and I was under the impression ERPNext will have a report builder specifically for the Financial Statement Reports like Balance Sheet, Profit and Loss
Well make no mistake this is a power tool, with the options and flexibility to handle whatever task you need it to do if you are prepared to work with it.