Speeding offences in Spain are the responsibility of the driver, whether the car is privately owned or rented. The owner of the vehicle is obliged to identify the driver, and rental companies usually charge their customers when they are obliged to provide their data to the authorities.
Car rental with Spanish plates
The rental company may charge a fee for identifying the responsible party. If the driver has a foreign driving licence, you cannot get points. The driver will be notified in Spanish, but it is possible to receive telephone assistance in English. If it is necessary to send information to identify the driver, to contest the fine or to provide proof of payment, it can be done in Spanish or in English.
Rental car with foreign plates
The rental company may charge a fee for driver identification. If the driver has a foreign driving licence, no points can be added for offences committed in Spain. Official notification will be made in the official language of the country where the car is registered, and all communications with Spanish traffic authorities can be made in Spanish or in that language.