I was told by my Carnival Travel Agent that the only way to get the discount is if you book under the "Early Saver" rate. BUT I just received awesome discounts for five rooms. Three of the rooms were booked under early saver and then we added the 4th / 5th room about two weeks prior to the trip. But I will admit that I tied the reservations together.
Anyway, go to www.carnival.com/earlysaver
and fill out the very simple form. You'll need your booking number, boat name, sailing date, where you saw the cheaper rate and what was the cheaper rate. But I've also read that this only works if you booked directly through Carnival. If you used an independant TA, call them and they have to do it for you.
We set sail on Mon June 1st. I filled out the form mentioned above on all five rooms (only expecting to get the rate adjustment on the first three rooms but figured 'what the heck". We originally paid $329 PP for 1/2nd person in each room and a reduced rate on the 3rd/4th people in a couple of the rooms.
Anyway, to make a very long story short, on the first three rooms (two double occupancy rooms and one four occupancy room) we received d a total of $1,330 in On board credits. After setting aside $40 PP for the gratuity, we ended up splitting the remainder and each person had well over $100 to blow on the spa, alchohol, gift shops, fountain fun cards, and photos. The deal that we had found was $159 with $50 OBC.... So as you can see it was a great price drop.
On the other two rooms that were booked only two weeks prior to the trip, they too got the discount when I asked! They had a three person room and a four person room. They ended up with $105 PP in OBC.
I do need to mention this though. When you fill out the form, they're supposed to send you an email of acceptance or refusal within forty eight hours. We arrived in Florida on Sat. a.m. (almost 48 hours from the time I completed the online forms). I waited till around lunch time and called carnival and they forwarded my call to the department that handled the earlysaver rebate center. They showed record or receipt of my request but it had not been processed. While on the phone, the first three rooms were processed and I called back a couple of hours later and they had processed the 4th/5th room.
When we arrived on the boat, however, our new wonderful OBCs did NOT show up. I went to the pursur's desk and checked, told her the amounts that each room was supposed to get and she said that they would be posted to our rooms within twenty four hours. The first night we just used the cash we'd put down on each card but by the next a.m. the OBC was available on our accounts. Even my kids cards, which did not have charging privelages, worked with the OBC credit.
Just make sure you fill out that form (or have your TA do so), take record with you of your reservation number, and if you don't see an email regarding your request within forty eight hours, call them and make it happen. It's worth the effort.
Also, you can ask for the discount up to forty eight hours before your day you board the ship (so you can request on Sat. a.m. and board ship Mon p.m.).....
Good luck, and enjoy the credits!