Require communications from Private Parking companies to be traceable/trackable

PoFA 2012 requires that a letter to keeper is delivered within 14 days of an alleged infringement but that it can be assumed that such a letter was delivered on the 2nd day after posting. In modern Britain, I believe that expecting the post office to deliver that quickly is unreasonable, and this makes the system open to abuse by parking operators, who can claim to have sent letters that don't arrive. This potential abuse could be avoided if all letters of this type were tracked and traceable.