I've cancelled a couple of reservations that I booked using certificates. Both times they were unable to issue me a new cert and put a note on my account to credit me for the points when I made my next reservation. The points didn't show up in my account immediatly but there was a note on my account. One of the agents emailed me a confirmation that the points would be there when I needed them, the other said she wasn't allowed to email me the confirmation. In both cases the points were there when I made my reservations a month or two later. In both cases I had certificates for a cat 4 hotel and used the credited points along with my own points to stay at a cat 6 hotel. I liked this option as it didn't tie me to a cat 4 hotel.