On the top it says CHARGE NOTICE. Thats a bit tricky with the wording, obviously to SCARE you, as private parking companies must indicate it is a Parking Charge Notice,
not Penalty Charge Notice(enforceable by the likes of po-po, councils, cnuts in suits, TFL et etc)
I may be wrong, its otherwise know as a "speculative invoice"
If you do abit of digging on the web most, if not all of these companies print their solicitor letters from the same printers.