Originally Posted by green_rd
I think it depends on the source of the OBC. If it is part of a promotion then it is usually use it or lose it. If it is for $ spent by somebody (pax or TA) you should get it back. Unless you have already made final payment you should see the fuel charge disappear from your final payment.
You've hit the nail on the head. There are "refundable credits" and "non-refundable credits". As Green stated: If it's part of a promotion then it is not refundable (you won't get cash back). If your TA or someone actually "purchased" and OBC for you then it's refundable. This is why some folks have told "Use it or lose it" and others have received refunds.
Most "non-refundable credits" cannot be used for gratuities or the casino.