In the past, I have dropped off the car at the Dolphin, and the valet has taken the car, returned to give me the keys, and I've gone inside to get my receipt. Last month the guy taking my car said I didn't need to do anything if I had already paid. I was hesitant to leave without the receipt, but checked into my hotel (Swan) without personally returning the keys to the National counter and getting a final receipt. I stopped by the National desk a few hours later when I was back at the Dolphin, and the keys hadn't been returned yet. I checked my credit card statement online when I got home to make sure I wasn't charged for any extra time, and the charge was correct. Still, next time I will ask to return the keys myself.