The car rental deposit, also known as a pre-authorization, is a sum of money held against your credit limit for the rental company's safety. It is not charged as a regular purchase but is held for the duration of your reservation. The deposit is processed when you pick up your rental car, but rest assured that the full amount is returned directly to your balance after you drop off the car in the same condition as when you picked it up. This ensures a hassle-free refund process.