Assuming that the bill that was sent you pertained to your property that is in a planned unit development subject to association dues, then most likely under the recorded covenants, conditions & restrictions, bylaws and rules, other owners in your complex are entitled to see the invoice sent to you and you are entitled to see their invoice since all homeowners are interconnected with respect to their dues for their units.The best way to resolve the dispute that you have written about is to have a face to face meeting with the person who sent the invoice that you are writing about.