How to find errors in a quickbooks bank rec

First export the key information from QuickBooks.  Use Ctrl-F to find transactions for the bank account you're looking to reconcile.  Make sure you only export the uncleared transactions.  No reason to look at already cleared transactions.

Then you need to get the actual bank information in to Excel  Every bank has some kind of export.

Then you need to make sure that the signs (the positive and negative) are correct so you may need to add a little calculation.  I suggest that positive numbers increase the bank balance and negative numbers decrease the balance.  

Then select the range of uncleared items from QuickBooks.  Then press Select Range # 1.  Then Press OK.   Then do the same thing for the bank transactions.  Press Range #2.  Then Press OK.

Then press Compare Ranges and you will see all of the differences.