You have to be at least 21 years of age to rent a car with Kalrental. The driver must have held a valid driving license for at least one year before the age of 21. Under-25s are subject to underage driving fees. There is no upper age limit for driving a rental vehicle with Kalrental, although we apply a senior driver’s fee for drivers over 70 years of age. A driving license valid for at least one year is still required.