This could happen when you have transactions recorded before the opening balance date.
Let’s take an example where you have entered $1000 as opening balance dated on 01-01-2016. But, you have a transaction recorded for $500 on 25-12-2015. In this case, the opening balance amount would take account of the $500 income and will display the opening balance as $1500.
To rectify this issue, it is advisable to set opening balance to a date before the date on which the transaction was recorded.
and GST filing.