I got the couon from when I joined traveler's advantage on AOL. I don't know if it was only good in the US but when I first reserved the car, I included all the promotional information from the coupon in my e-mail. They e-mailed me back a confirmation and said they would accept the upgrade. I did however keep a copy so that if I had a hard time I could prove to National that they had given me that rate. Fortunately, I didn't have a problem.