Discover Card offers to let you redeem $20 of cashback bonus for a certificate that is supposed to be worth $40 at Enterprise, a certificate that is supposed to be worth $40 at Thrifty, or a certificate that is supposed to be worth $40 at Alamo.
Enterprise's website said they had cars. On Discover's site, I found the code (DISCBB) to tell Enterprise's website that I am using one of the certificates ( https://www.discovercard.com/cardmem...modeCode=CP092
), and it says that "No black out dates apply" ( https://www.discovercard.com/cardmem...lPartnersTerms
). However, if I try to reserve online with the code, it says that they sold out and there will be no cars available; if I then start another browser window and do not mention the certificate, it says that there are cars. So they do have cars, just not for anyone using the $20/$40 thing. I thought of calling on the phone, confirming that a car was available, and then saying, "oh wait, I have this certificate", but the rules for the Enterprise certificate require you to use a special phone number and say that you cannot use it at the regular phone number. So they know as soon as your dial. Clever.
I next tried Alamo. Discover's site ( https://www.discovercard.com/cardmem...lPartnersTerms
) admits "Blackout dates may apply", but does not say what those dates are. Also, it says that you do not receive the code until you redeem the cashback for the certificate ( https://www.discovercard.com/cardmem...modeCode=CP198
), so you cannot check in advance to see if you will be able to use it.
The only other rental car company for which I can get the certificates is National, but National charges over $40 more (without the certificates) than other rental car companies at the airport where I am going, so it would cost more using the certificates at National than renting from another company without the certificates.
I do not think that you can even get back the $20. I think you lose it.