I will have to call Carnival to see if they have the same form with the Carnival email and mail and fax numbers to send it to. Doing Carnival Breeze in Europe in October.
Glad I pay for those Future Cruise Credits onboard a ship. They are even more valuable than Shareholder's Credit (I feel pretty sure you can use them BOTH...as the Future Cruise Deposits are Carnival's marketing deal that you can use on ANY sailing) and Shareholder's Credit is for owning 100 or more share of their stock. Hope so. They have in the past.
Otherwise, I wouldn't pay for those Future Cruise Credits while onboard and have my money in their hands til I decide on a cruise.
If you KNOW you are going to do especially a long (12 nights or longer) cruise, you buy the Future Cruise certificate for $100 onboard, then you use that as your "deposit" and they take that $100 you already spent off your cruise (no big deal there...you've paid upfront the $100 anyway). BUT with 12+ nights, you get an ADDITIONAL $200 OBC.