Not exactly, but you do have a reasonable amount of time to add the car to your policy. It's obviously best if you call your insurance company from the dealership to add it to the policy, but if you wait until you get home, or even a few days, that will be ok. The main problem you could have is that if you only have liability on the first car, then that's all you'll have on the second car if you were to get into an accident before you officially add it. No comp, no collision, etc. You'll have the same coverage that you have on the first car, no more and no less.