Replacement costs For newer makes and models, the car key is often part of the vehicle's security system. If you lose the key you may have to get the system re-coded.
If the key is damaged, and needs to be replaced, you should be able to get a replacement key from your local dealer. If you lose the key, but it's unlikely to be used by anyone else - for example, you drop it over the side of your boat while fishing and you still have the master key, you should be able to get a replacement from your dealer.
You generally get two master keys with a vehicle, the master key operates everything in your vehicle, and is programmed for your car, so replacing it can be inconvenient and time consuming. If you lose your master key and you don't have a spare, you may need to replace the body control module or at least have it reprogrammed.
If your keys are stolen and it is possible that the thief could come back and steal your vehicle, you will need to reprogram or even replace your vehicle's body control module for peace of mind.
Keep a spare master key in a safe place
If you do not have a spare key, have one made as soon as possible. Check the vehicle manufacturer's handbook for key details and follow the instructions about code details.
If purchasing a used car, make sure the seller gives you a complete set of keys, since obtaining additional keys later could be a difficult and costly process.