We've updated the balance tool to allow you to specify an end date or apply to all transactions. We'll look into providing a visual on your last balance date.
Date of last balance
Now that my balance works, I'd like to reccomend that we update the balance tool to capture a date. So the balance should happen according to the ending date on the statement. Once we capture that, we should display the date under account properties or when we show transactions for a particular account. This way its easy to see what account have been balanced and as of when.