We will be in Barcelona in September and want to rent a car and drive into France. Will there be extra fees for taking the car into France, even though we will be returning the car to Barcelona? We would most likely be renting the car at the Barcelona airport.
There should not be since you are returning to Barcelona. However, check with the rental company. Sometimes the car may not have the appropriate tax stamps, etc., necessary to drive in another country.
We did the same thing last year and had no issues from the rental agency. But always alert them that you will be doing so.
FYI - To legally drive in Spain, you must have an International Drivers Permit along with your state drivers license. In the US, you get them from AAA.
It is standard procedure to tell the rental agency your countries of travel when you make the reservation, but this is not one of the areas where that info will raise any red flags. There are no checkpoints at the border crossing. France charges highway tolls on a per-kilometer basis (rather than with a pre-paid tax sticker, etc).