I searched the forums and FAQ and couldn't find this, but basically:

I'm not running a business, really just testing out Zoho Invoice, but whenever I remember, "Oh no, I need to go add the payment" it's usually after the due date.  Zoho lets me choose a Payment Received date, but even if I choose a date that is before the entry date, it still says there is a late fee.  Is this a bug or am I doing something wrong?