The other delightful thing about carnets? If your ferry or plane or whatever arrives at the customs post after the carnet office (at which you must check in, usually behind a long line of articulated lorries) is closed, Tough Cheese. You spend the night and wait, or else pay a fortune. Voice of experience (and a near-miss) on that one, trying to drive a concert harp though various European borders. Getting our car through the Berlin Corridor in (then) East Germany with all their police checks was easier. I'm not kidding.

And make sure you get the Right Kind of carnet - there are (or were in those days) a bunch of them. And they are HELL to fill out. Makes VAT forms look like kindergarten scribbling.