The kilometers driven and fuel level are automatically calculated by the Auting Connect device installed in the car.
Any extra charges have to be reported by the owner within 36 hours after the end of the reservation.
If the Driver does not return the car with the same fuel level, the difference is automatically calculated based on the car's tank size and a price per liter set at the national average price defined by the Ministry: https://dgsaie.mise.gov.it/prezzi-mensili-carburanti