Please note that you can undo only the most recent reconciliation. But, if the reconciliation which you wish to edit is not the most recent one, then you will have to delete all the other reconciliations up to the one which you wish to undo. So for example, if you had selected the wrong check while reconciling 6 months ago, you will have to undo all reconciliations done in last 6 months.
The steps to undo a reconciliation are as follows:-
and GST filing.