Well, when you make your AutoEurope reservation--they provide you with the "voucher"....which is probably like a confirmation or reservation number. (They price match after you make the reservation with them.) There is no cancellation penalty that I can see, if you change your mind. I've never booked with AE, but am about to soon.

Problem I'm having is that I can get a killer rate with one of the Avis codes, without insurance or any extras. But as soon as you add CDW, liability, etc, the rate more than doubles (in my case)! And at that point, it actually becomes higher than AE's "inclusive" rate (with insurance coverages already added). And, of course, in order for them to price-match, gotta compare apples to apples. C'est la vie....