I have shown up late for car reservations recently (due to flight delays), and sometimes when I pick up my Hertz car (at IAD), the reservation start time is when I originally was supposed to be there -- up to "24 hours ago." Thus, the amount that they attempt to charge me is for the full reservation. Be wary of that.

Otherwise, no, I'm not aware of a no-show fee or cancellation fee.

-mvitale